Experimental Chemistry II
Experimental Chemistry II CHEM C1260
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PHYSICAL REVIEW A 79 013628 2009 Multiscale theory of nitesize Bose systems Implications for collective and singleparticle excitations s Pankavich z Shreif1 Y Chen3 and P Ortoleval 1Centerfar Cell and Virus Theory Department of Chemistry Indiana University Blaamingtan Indiana 47405 USA 2Department of Mathematics University of Texas at Arlington Arlington Texas 76019 USA 3Department of Physics Purdue University West Lafayette Indiana 47907 USA Received 18 August 2008 published 29 January 2009 Boson droplets ie dense assemblies of bosons at low temperature are shown to mask a signi cant amount of singleparticle behavior and to manifest collective dropletwide excitations To investigate the balance between singleparticle and collective behavior solutions to the wave equation for a nite size Bose system are constructed in the limit where the ratio a of the average nearestneighbor boson distance to the size of the droplet or the wavelength of density disturbances is small In this limit the lowest order wave function varies smoothly across the system ie is devoid of structure on the scale of the average nearestneighbor distance The amplitude of short range structure in the wave function is shown to vanish as a power of a when the interatomic forces are relatively weak However there is residual short range structure that increases with the strength of interatomic forces While the multiscale approach is applied to boson droplets the methodology is applicable to any nite size Bose system and is shown to be more direct than eld theoretic methods Con clusions for 4He nanodroplets are drawn DOI 101103PhysRevA79013628 I INTRODUCTION Quantum clusters QCs are assemblies such as quantum dots 173 super uid droplets 476 fermion droplets 78 superconducting particles 910 and other structures 1112 They involve processes simultaneously acting over multiple scales in space and time from the interaction of individual particles to dropletwide collective dynamics There have been a number of studies presenting theories of their properties and selected citations are provided above However none appear to address the multiscale character of a QC or introduce a framework that takes full advantage of the separation of scales as a way to solve the wave equation Recently it was shown that the wave equation for a fer mion quantum nanodroplet can be cast in a form that explic itly manifests its multiscale character 13 This formulation enables a deeper understanding of the interplay of angstrom and nanometer scale processes underlying the unique behav iors of a fermion QC imposed by the exclusion principle The objective of the present study is to introduce a novel technique that builds in characteristics of lowtemperature boson droplets he central concept of our earlier approach 13 is that there are two or more distinct spatial scales of motion for the constituent fermions in a QC One is the short characteristic ength ie the average nearestneighbor spacing This short scale is If 3 for average number density n within the QC A second characteristic length is the QC diameter The ratio 9 of the smallerto larger of these lengths was introduced to enable a perturbation method for solving the wave equation ile the interaction potential for a condensed QC is large and thereby cannot serve as the basis of a perturbation analy sis 9 for a QC of 1037106 particles is small say 10 1 to 0 Thus 9 presents itself as a natural candidate for the basis of a perturbation theory of QCs that could yield accu rate approximations even for strongly interacting systems 1050294720097910136288 0136281 PACS numbers 0375Hh 0270Ns 0530Jp 6725dw In a boson QC there are two types of processes to be accounted for The QCwide processes are either collective eg rotations coherent density waves or shape oscilla tions or migrations of particlelike disturbances across the QC ie the coordinated motion of a given particle and a set of others responding to the rst For identical quantum par ticles the latter quasiparticle excitations are not identi able with a speci c particle In contrast to these global processes shortscale ones re ect close encounters of particles related to the interparticle potential For fermions the exclusion principle strongly affects these shortscale motions How ever bosons display the opposite tendency ie a quorum principle At low temperature all bosons tend to be in the same state ie at T0 all bosons are in the single particle like ground state for weakly interacting systems While the N atom wave function is observed to have some long range structure as expressed in the low momentum behavior of neutron scattering experimenm it is stated that only 10 of the 4He atoms are participating in this Bose condensate like behavior 14716 This seems to be a re ection of the strength of the interatomic forces in a 4He liquid In the present work we explore this effect seeking to show how short scale structure increases in intensity as the strength of the interatomic forces increase In particular we seek a de scription wherein the N atom wave function can be under stood as a short lengthscale factor with variability that in creases with the strength of the potential multiplied by a long scale envelope factor representing collective modes We suggest that this is a distinct picture from that wherein it is stated that 10 of the particles are in the Bose condensate BBC and 90 are in higher momentum dressed single par ticle states ie the N atom system cannot be understood in this fashion All atoms participate in the collective motion and are part of the quasiparticle response Though the multiscale analysis is demonstrated for boson droplets the approach also applies to trapped atomic Bose 2009 The American Physical Society PANKAVICH er al Einstein condensates with typical interatomic distances be tween 01 and 1 micron and system size ranging from 1071000 microns hence containing between 1037106 atoms 1718 In the atomic Bose condensate the interatomic in teraction can be tuned by a Feshbach resonance 19 The study of strongly interacting trapped BECs near a Feshbach resonance has een a subject of active investigation 171820725 Many properties such as the condensate frac tion and collective mode frequencies can be modi ed near the Feshbach resonance 222 Such strongly yet still short ranged interacting Bose condensates offer an interesting middle ground between the weakly interacting BEC well described by mean eld theory and 4He super uid with strong and longer range interaction More recently trapped BECs with longrange dipolar interactions have also gener ated much interest 2627 In the present study we attempt to rigorously determine the limiting behavior of the wave function for boson QCs as ea 0 The objective is to develop a theory of boson droplets by integrating these notions into a multiscale theory valid for strongly interacting nite Bose systems described above The e is a long history of multiscale analysis for Nparticle systems 28739 Most relevant is the analysis of the classical Liouville equation wherein one identi es order parameters that characterize the slow and long lengthscale behaviors of a system and mesoscopic equations for the sto chastic dynamics of order parameters are derived 40753 These order parameters describe nanometer scale features such as the position orientation and major substructures of a nanoparticle 52755 The ansatz starting the analysis is that solutions to the Liouville equation ie the Nparticle prob ability density depend on the atomistic con guration both directly and indirectly the latter through the order param eters Other approaches for quantum systems eg truncated Laplace transformation of the interaction potential and quan tum mechanicsmolecular mechanics 56765 have been de veloped but are distinct from the elength ratio perturbation approach developed here and do not yield a rigorous meso scopic wave equation for QC dynamics The ansatz that starts our multiscale QC analysis is that the wave function 1 re ects a dual dependence on the con guration of the N bosons in the QC Let F1F2 f be the set of positions of the N bosons assumed identical By choice of units the position f of particle i is displaced a distance of about one unit when it moves a distance If In contrast RerZ changes by a distance of about one unit as particle i traverses the entire QC Denote the collection of these scaled positions by RR1R2 RN To capture the distinct types of behavior long and short scale we hypoth esize the wave function 1 has a dual dependence on con guration ie 1 R This dual dependence is not a viola tion of the number of degrees of freedom 3N Rather it is a way to express the distinct ways in which 1 depends on the droplet con guration We show that if 9 is small the two distinct dependencies of 1 can be constructed via a multi scale perturbation technique Hence multiscale analysis naturally reveals the implications of these notions for a bo son QC PHYSICAL REVIEW A 79 013628 2009 II MULTISCALE FORMULATION The behavior of a lowtemperature boson QC is now ex plored via multiscale analysis We demonstrate how the in dividuality of the particles is lost yielding QCwide coop erative dynamics The absence of a Fermi level makes it dif cult to track the number of particles in a given region of space Thus the system lapses into a collective delocalized bosonic presence without a wellde ned sense of the indi viduality of particles However strong interactions between particles as in liquid He are expected to induce shortscale character in the wave function In this section we show how delocalization can emerge naturally from a multiscale analy sis of the wave equation for a boson QC We rst consider the case of relatively weak interactions and then explore the effect of stronger ones and the inclusion of shortscale struc ture in the wave function A Weak interactions delocalization and residual shortscale structure To begin the development we formulate the wave equa tion in a mariner that reveals the lowenergy excitations of interest at low T While our formulation facilitates the dis covery of the nature of the hypothesized delocalized behav ior selfconsistency would preclude the drawing of false conclusions since we begin with the full wave equation Let U be the Nparticle potential E mund be the ground state QC energy and de ne the deviatoric potential V U Eg roun Introduce the characteristic kinetic energy ZmL2 for each of the N bosons where m is the particle mass and L is the size of the QC The position of particle i is denoted LRi for dimensionless vector R In these variables the dimension less Hamiltonian H is de ned via 1 H v2VEKV 1 while the dimensional Hamiltonian is H 2H mLZ For this E mundshifted Hamiltonian the groundstate energy is zero and V U Egmund The dimensionless wave equation takes the form H 1 E 1 where E is the dimensionless deviatoric energy Let I be If ie l is the typical nearestneighbor dis tance within the QC of number density n Then the length scale ratio is given by 221 L With the above de nitions R changes by a distance of about one unit as particle i traverses the entire QC In contrast F E e lR changes by a distance of about 2 1 as particle i traverses the entire QC and by about one unit when it traverses one nearestneighbor distance 1 Thus the Rt s are natural for tracking QCwide disturbances while the f are ideal for characterizing close particleparticle encounters With this our multiscale ansatz is that 1 has the dependence 1 f1F2 fNR1R2 RN9 The dual de pendence of 1 does not constitute a violation of the number 3N degrees of freedom Rather we shall show that it is a re ection of our expectation that 1 depends on the Nboson con guration in two distinct ways That both dependencies can be constructed is shown below to be achieved in the 0136282 MULTISCALE THEORY OF FlNlTESIZE BOSE small 9 limit The multiscale wave equation with f1FzN and RR1R2RN follows from this ansatz and the chain rule H0 9H1 SZHZW Eur 2 where E 92E and 1 2 1 2 H0EY03 H1 Y0 Yia H2 EY1V 3 Here V0 is the 5 gradient and V1 is the 8 gradient The objective of our multiscale development is to con struct an equation for the mesoscopic wave function MR which varies smoothly across the QC lt1gtR J39 derUi er 1 r 4 The sampling function A is a Gaussianlike expression which in 5 space is centered at about 9 11 is unit normal ized and has a halfwidth that is much greater than one 5 distance but is much less than the QC diameter A central theme of this study is that one may derive a selfconsistent equation that is closed in I in the small 9 limit A perturbation solution to the multiscale wave equation is constructed as a Taylor expansion in 9 ie I Eio l n9 To 090 one obtains the eigenvalue problem with zero potential HO I O EO I O 5 Since we seek normalizable solutions which decay to zero as Mew I o must be independent of r This is consistent with the physical nature of the problem ie as a QC is of nite size about one unit in R1 and H0 is a free particlelike Hamiltonian the lowest order problem only admits an independent solution The absence of smallscale structure in I o implies E0 is zero and Po 003 6 for D0 to be determined in higher order While it is clear that Datbo as 9gt0 it remains to show that DO can be con stricted in a selfconsistent procedure Using the 090 analysis ie E020 the 09 equation becomes Ho l l H11r0 Euro 7 Since PO is independent of HI I O vanishes Hence the righthand side of Eq 7 is independent of g and thus HO I I must be independent of 5 Using the normalizability and de cay conditions ie I l vanishes at in nity We nd that PI is independent of g and E120 To 092 one nds that since 1 0 and PI are independent of r How2 HZ I O Euro 8 To arrive at an equation for Do we a multiply both sides of Eq 8 by the sampling function A and integrate over 5 b use the divergence theorem and properties of A c neglect PHYSICAL REVIEW A 79 013628 2009 surfacetovolume terms and d use the fact that DO does not change appreciably within the sampling volume ie the region wherein A is large With this one obtains the meso scopic wave equation 1 5 V09 0 EM 9 upon noting that dgtgtdgt0 as 9gt0 and de ning 7 via V03 f d3NrAR rVr 10 Even if the bare potential is short range ie independent of R 7 depends on it due to the Rcentered local averaging manifest in the sampling function A Since E is the deviatoric energy E0 ie En0 for every n must be an eigenvalue corresponding to the ground state solution of the original problem Hence E220 is an eigenvalue of the mesoscopic Eq 9 and 10 While singleparticle character in D0 is lost it was present in the original wave equation The question arises as to how it was lost This can be addressed by subtracting Eq 9 from the wave equation 8 to 092 One obtains gm Mr 7Rldgto o 11 This is a 3N dimensional Poissonlike equation with charge density equal to 2V l7lgt0 Being proportional to Do the source term is limited to the region within the droplet if Eq 9 supports boundstate solutions Through V the charge density has shortscale ie individual particle character with variations over distances of order If This implies that although all individual particle character in 1 0 and W1 is lost there is residual particle character ie oscillations in the wave function across 5 with amplitude of 092 For a 1000 boson QC 9 2101 the single particle character of the wave function is two orders of magnitude smaller than the overall pro le as expressed in D0 Since W2 is proportional to D0 and D0 is zero outside the QC particlelike character is con ned to the interior of the QC as expected We conclude that the multiscale approach to boson QCs constitutes a self consistent picture and yields insights into the nature of low temperature boson QCs when boundstate solutions to the mesoscopic equation 9 exist B Strong interactions and induced shortscale structure The above development is now revisited but for the case where the potential is strong scaling as 9 1 in particular we let the potential be 9 1V With this H1 is now V1V0V V The rationale for subtracting 7 is clari ed below We nd that l7 is small when the smoothing volume is appre ciable ie averaging the large positive core potential with the weaker longrange attractive tail leads to partial cancel lation in l7 as demonstrated for helium in Sec HI Thus we assume 7 is 09 To preserve the full potential we put 7 in H2 having denoted 7 as 9 7 0136283 PANKAVICH er al With YO I 020 and the above Eq 7 becomes HO P1V l7 1 0 1 1 0 12 Multiplying both sides by A integrating over all 5 using integration by parts and neglecting higher order terms in a one obtains 120 Hence PI is the solution of rm W erbo 13 Separating variables one solution to Eq 13 is of the form I 1BRIgt0R where B satis es i738 m We 14 Thus I is seen to have shortscale structure of amplitude 0a and not 022 as in the case of weaker interactions Sec II A The 022 problem now reads 1 Howz Y139 0YOB EYIdDO IBV V V1430 E2 0 15 Upon multiplying both sides of Eq 15 by A integrating over 5 using the divergence theorem and Eq 14 and ne glecting surfacetovolume ratio terms one obtains a meso scopic wave equation for D0 similar to Eq 9 i7 003 W19 4 Em 16 C13 J39 d3NrAR erlYoBrRl2 17 As seen from Eq 14 B is a response to the uctuations of the potential difference V I7 1m gradient with respect to 5 re ects shortscale structure in the derivative potential Thus one might expect that is a type of kinetic energy con tribution that adds to the potential 7 driving the dynamics of Do In the next section we consider a different analysis using numerical techniques and a calibrated potential for 4 He III APPLICATION TO 4He To explore the implications of the theory of Sec II we developed computational procedures and applied them to 4 e We consider factors affecting the behavior of a He nanodroplet and the structure of our multiscale approach These include averaging length kinetic versus potential en ergy the effective wavelength of the bosons and droplet Size Let the distance over which a Gaussianlike function 7 is appreciable be denoted g and let 7 be unit normalized The smoothing function A of Sec II is taken to be a product of N factors 7R ef il2 N where is 7 a normalized PHYSICAL REVIEW A 79 013628 2009 Gaussianlike sampling function The smoothed potential I7 for pairwise bare interaction potential 1 takes the form V03 2 01R 6 18 K where mpg f d3r1d3rzrai 513705 swarm 19 From symmetry the smoothed potential 17 only depends on the distance RU and through 7 the smoothing parameter To investigate the character of 17 we chose vr to be the Aziz potential 66 A numerical code was written to evaluate the sixfold integral in Eq 19 taking advantage of symme try Pro les of 17R g for various values of g are seen in Fig 1 These pro les show that the smoothing parameter has a drastic effect on the position of the minimum well depth and overall shape of the potential As increases interpar ticle distance at the minimum and well depth both increase Thus as g grows larger 17 becomes strictly positive and monotonically decreasing since the repulsive core dominates the attractive tail and causes the well to disappear The bare potential 1 has a shortrange repulsive core of radius about 1 and a longrange attractive tail with range of several 1 With this pairwise interaction it is expected that if g is smaller than I then 17 is roughly the same as the bare potential 1 Hence D0 would have shortscale character in contradiction to our assumption ie D0 depends on 8 not 5 If g is large ie similar to the size of the 4He nanodrop let then 17 is small ie for most of the range of integration underlying the averaging in 17 the values of 17 are small and contributions from the repulsive core and the longerrange attractive tail tend to cancel Thus for large 7 would not support bound states and the excitation energy E2 depends strongly on the choice of g This implies that a selfconsistent procedure must be invoked for choosing For example one solves the mesoscopic wave equation for 1003 g with cor responding excitation energy 2 and then minimizes 2 with respect to g Such a strategy is equivalent to construct ing the functional i2 whose minimum over all Do is the solution to the mesoscopic wave equation and then minimiz ing this functional with respect to both D0 and g As the pro le of the effective potential changes so does the energy i2 There are several estimates of kinetic and potential energy to be considered If L is the diameter of the nanodroplet then 7 122mL2 is the kinetic energy associated with the longest wavelength bosons In contrast the rest en ergy is wZ where wzzkm and k is the second derivative of the bare potential evaluated at its minimum A re evant potential energy is the well depth for the bare potential while another is that for 17 In Table I we present values of these energies in addition to information about the potential well for differing values of g with nanodroplet size N 103 and 106 Due to the symmetry of Eq 19 the position of the 0136284 MULTISCALE THEORY OF FINITESIZE BOSE n3s WEE K R A g nsn RE K 39a 4m 4m Rm son 59D em 5 nsn WR K 5442 590 447 947 740 799 R 1 FIG 1 Graphs of the effective potential for NlO3 particles in nanodroplet with differing values of smoothing parameter a 035 b 060 c 090 respectively minimum should change by a factor of 9 as N increases from 103 to 106 At low temperature boson nanodroplets display collective behaviors wherein individual particle detail gives way to nanoscale order parameter dynamics Analysis of the meso scopic wave equation for boson nanodroplets yields implica PHYSICAL REVIEW A 79 013628 2009 tions for 4He droplet dynamics including quantized surface waves ie morphological oscillations Quantized vortices in thin lms 67 suggest that there may be related excita tions in 4He nanodroplem Table I Computations with the present theory involve construct ing the order parameter R pro le This can be accom plished via a variational principle based on a functional whose minimum is attained for D0 expressed as an N fold p product With this p satis es 1 5 var ltp Ema 20 Nve am i f dWvaiwaimpa N MN MR 21 for functional derivative 8 8ltpR and threedimensional Rspace Laplacian Vi This constitutes a nonlinear eigen value problem to determine p and the energy E States in the form of an N fold product of a single p function are not necessarily the lowest energy excitations Expanding the set of admissible functions could lead to lower energy states Furthermore that these order parameters can be imaginary is central for capturing droplet analogues of quantized vortices Table I If one adopts a quasiparticle perspective then the nano droplet consists of particles of a broad range of wavelengths The longer correspond to the droplet diameter for them all detail of the bare potential is lost ie they experience an effective potential which is small due to averaging the re pulsive core and attractive tail For shorterwavelength qua siparticles details of the bare potential are experienced and shortscale structure is induced by the potential Choosing greater than I but much less than the droplet diameter yields the wave function I Belgt0 from Eq 13 which captures the range of elementary excitation wavelengths If g is suf ciently large but still much less than the nanodroplet diam eter then a mean eld approximation for D0 should suf ce ie each boson is interacting with many others so that an effective eld is an accurate description IV RESULTS AND CONCLUSIONS A mesoscopic wave equation for boson QCs was derived using a multiscale approach It was shown that properties of boson QCs can be derived via a multiscale perturbation analysis of the wave equation even when interactions be tween the bosons are strong Bosons in a droplet at low T were shown to act in a collective manner losing much of their individual character Lowlying excited state solutions of the mesoscopic wave equation have pro les without spa tial variations on the n 3 scale at which one would other wise expect to re ect the presence of individual bosons Rather individual particle features merge via the averaging imposed by the smoothness of the wave function A effective N particle smoothed interaction potential I7 0136285 PANKAVICH er al PHYSICAL REVIEW A 79 013628 2009 TABLE I Table of values describing energies of the effective for given value of g and bare potentials annonic Position Bare rest oscillator Ground state Kinetic Size of Smoothing Depth of energy fwi energy energy of nanodroplet parameter minimum Depth of minimum k L E0 Nanodroplet N m A minimum m K m J m J m A m J m J 50 296 108 l49gtlt10 22 1108gtlt10 22 l303226gtlt10 5 680811 gtlt10 33 206gtlt10 14 N103 035 352 557 759gtlt10 23 060 440 l60 22l gtlt10 23 090 623 003 4l4gtlt10 25 N106 035 035 557 759x1023 060 044 l60 22l gtlt10 23 090 062 003 4l4gtlt10 25 emerges that only depends on dropletwide positional infor mation ie not on any n 13 scale features With the excep tion of highly excited states of the droplet I7 only supports coherent dropletwide dynamics The key technical achievement of the multiscale analysis is the derivation of a mesoscopic wave equation for boson droplet dynamics The methodology holds for a strongly in teracting boson droplet of nite size at low T The mesos copic wave function D0 depends on the set of N particle positions 8 which are cast in unim such that they change a distance of one unit as a boson traverses the entire droplet The result is in my 0 Em 22 me f d3NrArg ezwrz 23 where is the 3N dimensional Laplacian with respect to R and I703 is the bare N particle potential with the location of each particle averaged over a sampling volume containing a statistically signi cant number of bosons E2 is the excitation energy This mesoscopic wave equation is remarkable in that it holds for strong interparticle interaction strength as long as 9 the ratio of the average nearestneighbor spacing to drop let diameter is small ie for those with 1000 or more bosons As D0 is the lowest order wave function ie I HGDO as 8H0 it satis es boson particle label exchange symmetry PUQDO 10 24 for permutation operator PU As D0 is governed by the smoothed potential I7 much of the individual particle particle shortrange correlation is diminished This is essen tially a selfconsistency argument ie 10I7 Particle ex change symmetry and the averaging in I7 suggest that any one boson is not interacting with particular others ie in contrast to two body interaction This suggests that to good approximation d30ltp151ltp152 N for order parameter ltpR The single particle density pR is de ned via N pa PNRE 50 15ltIgto2 25 11 and hence is approximately Niltp1i2 Thus p is directly re lated to the number densit The above implies the boson droplet at low T is charac terized by the pro le of the order parameter ltpR which is devoid of short ie If scale features In this way all individual particle behavior is lost as 9 gt 0 Since the energy for shortrange forces as for 4He determined by Eq 1 is proportional to N the difference in energy for the N 1 and the N particle droplet the chemical potential is independent of N In this way there is no energy measure of the number of bosons in the droplet This is in sharp contrast to the situation for fermions ie due to the Fermi level The averaging in I7 suggests it is singleparticle like ie each boson evolves in a local potential eld N A V 2 MR 11 26 For 4He there is an attractive tail in the bare twobody po tential Thus we expect 17 to be as in Fig l for a spherical droplet More generally the threedimensional spatial pro le of 17 depends on droplet morphology and hence on p imelf This is accounted for in the local averaging embedded in Thus the order parameter p is determined by a mesoscopic wave equation with mean eld character The development of the present multiscale approach suggests that this is not just a crude approximation Rather it appears to be a conse quence of a the smallness of 9 for a droplet1 b the ex change symmetry constraints the quorum principle for bosons and c the smooth pro le of the wave function for low temperature droplets ie that there is no n 13 spatial scale structure in 1 except as an 022 correction A promising area for future developmenm is to extend these results to account for the scattering of atoms or mol 0136286 MULTISCALE THEORY OF FINITESIZE BOSE 8 FIG 2 Schematic depiction of a boson nanodroplet in a vortex like state of quantized undamped circulation ecules from a QC or the effects of external elds In work in progress we are applying the multiscale approach to trapped BEC systems as the interaction progresses from weak to strong and short range to long range to investigate the ef PHYSICAL REVIEW A 79 013628 2009 fects of interaction and to understand the evolution from weakly interacting BBC to a strongly interacting Bose sys tem such as He Such studies could facilitate the design of experiments to validate predictions of the multiscale theory Other natural extensions include the analysis of more com plex droplets such as those composed of fermions and bosons ie 3He 4He mixtures those with embedded solid nanoparticles or macromolecules or those with sustained in ternal circulation patterns Fig 2 ACKNOWLEDGMENTS This project was supported in part by the Indiana Univer sity College of Arm and Sciences through the Center for Cell and Virus Theory Additional support was provided by the Lilly Endowment Inc 1 R Nepstad L Saelen and J P Hansen Phys Rev B 77 125315 2008 2 C H Liu Phys Lett A 372888 2008 3 J T Shen and S H Fan Phys Rev A 76 062709 2007 4 J M Merritt J Kupper and R Miller Phys Chem Chem Phys 9 401 2007 5 L Lehtovaara and J Eloranta J Low Temp Phys 148 43 2007 6 J Lekner J Phys Condens Matter 12 4327 2000 7 F Stienkemeier O Bunermann R Mayol F Amcilotto and M Pi unpublished 8 R Mayol F Amcilotto M Barranco M Pi and F Stienke meier unpublished 9 S 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Phys 110 528 1999 49 M H Peters J Stat Phys 94 557 1999 50 W T Coffey Y P Kalmykov and J T Waldron The Lange vin Equatian With Applicatians t0 Stachastic Prablems in Physics Chemistry and Electrical Engineering World Scien ti c Publishing River Edge NJ 2004 51 P Ortoleva J Phys Chem 109 21258 2005 52 Y Miao and P Ortoleva J Chem Phys 125 044901 2006 53 Y Miao and P Ortoleva J Chem Phys 125 214901 2006 54 S Pankavich Z Shreif and P Ortoleva PhysicaA 387 4053 2008 PHYSICAL REVIEWA 79 013628 2009 55 S PankaVich Y Miao J Ortoleva Z Shreif and P Ortoleva J Chem Phys 128 234908 2008 56 P Y Ayala G E Scuseria and A SaVin Chem Phys Lett 307 227 1999 57 J Almlof Chem Phys Lett 181319 1991 58 S S Iyengar G E Scuseria and A SaVin Int J Quantum Chem 79 222 2000 59 C J Cramer Essentials afCamputatianal Chemistry Thearies and Madels 2nd ed Wiley New York 2004 60 A Warshel and M Levitt J Mol Biol 103 227 1976 61 V Gogonea L M Westerhoff and K M Merz Jr J Chem Phys 113 5604 2000 62 H Lin and D Truhlar unpublished 63 F Maseras and K Morokuma J Comput Chem 16 1170 1995 64 J Gao Acc Chem Res 29 298 1996 65 R T Pack and G A Parker J Chem Phys 87 3888 1987 66 R A Aziz V P S Nain J S Carley W L Taylor and G T McConVille J Chem Phys 70 4330 1979 67 V Ambegaokar B I Halperin D R Nelson and E D Siggia Phys Rev B 21 1806 1980 0136288 200 The Fermentation of P ruvate gtgt Ke C cap 5 Qgt Review In the process of glycolysis a net profit of two ATP was produced two NAD were reduced to two NADH H and glucose was split into two pyruvate molecules Qgt When oxygen is not present pyruvate will undergo a process called fermentation In the process of fermentation the NADH H from glycolysis will be recycled back to NAD so that glycolysis can continue In the process of glycolysis NAD is reduced to form NADH H If NAD is not present T glycolysis will not be able to continue During N fn m Magnum aerobic respiration the NADH formed in W m H M l2lc o gt NAD glycolysis will be oxidized to reform NAD for H a iZlMDIDMW W CH1 mum use in glycolysis again glucose 2 pyruvsla W mm m m When oxygen is not present or if an organism W W is not able to undergo aerobic respiration pyruvate will undergo a process called fermentation Fermentation does not require oxygen and is therefore anaerobic Fermentation will replenish NAD from the NADH H produced in glycolysis yenll iimlly immune One type of fermentation is alcohol fermentation First pyruvate is decarboxylated C02 leaves to form acetaldehyde Hydrogen atoms from NADH H are then used to help convert acetaldehyde to ethanol NAD results Facultative anaerobes are organisms that can undergo fermentation when deprived of pyruvate a Ilralml J o quot quotquot quot quot quot EH oxygen Yeast is one example of a facultative WHAM Wm 2 acclai lhydl 21 am anaerobe that win undergo acoho fermentation malty bacteria muscle cells A mam Some organisms such as some bacteria wtll undergo lactate fermentation Two J pyruvates are converted to two lactic acid me A I 3 molecules which ionize to form lactate In Immamum A m 39 NA H H are converted to 2 c M NAD a D Our muscle cells can undergo this process l owmgu e m when they are in oxygen debt If enough 04 Hmow quot3 oxygen is not present to undergo aerobic 2i Pymvlu val r 2 mm respiration pyruvate will undergo lactic acid fermentation wwwthinkwellcom inlothinkwellcom Copyright 2000 Thianeii Corp All Rights Reserved 031500bi0095 Chmielewski Group Literature Abstracts CHEMICAL BIOLClG r39 Modified Serine Controls Protein Phosphorylation Light releases serine protecting group permitting researchers to regulate cellsignaling mechanism Celia Henly Arnautl Protein phosphorylation which is a major mechanism of cell signaling can occur only on 0 certain amino acids including serine Peter G Schultz and coworkers atScripps Research I Institute report that they can control protein phosphorylation on serine residues by genetically incorporating a photoprotected serine analog into proteins Nat Chem Biol 0 DUI1U1DEEllnchembioiuuialal Phosphorylation can39t occur at the protected serine residues Elut shining blue light on the protein remoyes the 45dimetholryEnitrobenzyl protecting group thereby exposing serine and making it ayallable for phosphorylatlon residues in Pho4 a yeasttranscription factorthat regulates genes and allows the organism to grow at differentinorganic phosphate concentrations Ely replacing one serine residue at a time with the photoprotected analog the team was able to obserye the effects ofbloclting pbosphorylation at speci c sites and measure dynamic responses to the phosphorylation H 2r The researchers used the serine analog to regulate phosphorylatlon of speci c serine 2 syent O PHDTDECllITRUIL Light cleaves bulky nitrobenzyl group from serine Once exposed the serine residue can be phosphorylated September 2007 Contributing Editors Stefan Hershberger Science Marcos Pires Nature and Nature subdivisions Brandon Gaddis Iris Geisler JACS J ee Yeon Lee PNAS Dawn Ernenwein ACS Chemical Biology Chem Biol amp Drug Design Dave Przybyla Angewandte Chemie Hilda Namanja Chem amp Bio Nicole O Neil Org Lett Nature Chemical Biology Terrequinone A biosynthesis through Ltryptophan oxidation dimerization and bisprenylation Nature Chemical Biology 3 584592 2007 Carl J Balibar Annaleise R HowardJones 81 Christopher T Walsh The antitumor fungal metabolite terrequinone A identi ed in extracts of Aspergillus sp is biosynthesized by the fivegene cluster tdiAitdiE In this work we have overproduced all ve proteins TdiAdeiE in the bacterial host Escherichia coli fully 39 39 the 39 39 of 39 A This pathway involves aminotransferase activity headtotail dimerization and bisprenylation of the scaffold to yield the benzoquinone natural product We have established that TdiD is a pyridoxal 539phosphate7dependent Ltryptophan aminotransferase that generates indolepyruvate for an unusua nonoxidative coupling by the tri omain nonribosomal peptide synthetase TdiA TdiC an NADHdependent quinone reductase generates the nucleophilic hydroquinone for two distinct rounds of prenylation by the single prenyltransferase TdiB TdiE is required to shunt the benzoquinone away from an offpathway monoprenylated species by an as at unknown mechanism Overall we have biochemically characterized the complete biosynthetic pathway to terrequinone A highlighting the nonoxi ative dimerization pathway and the unique asymmetric prenylation involved in its maturation Science Asymmetry in the Structure of the ABC TransporterBinding Protein Complex BtuCDBtuF Science V01317 Issue 5843 13871390 7 September 2007 Rikki N Hvorup1 Birke A Goetz1 Martina Niederer1 Kaspar Hollenstein1 Eduardo Perozo2 Kaspar P Locher BtuCD is an adenosine triphosphateibinding cassette ABC transporter that translocates vitamin B12 from the periplasmic binding protein BtuF into the cytoplasm of Escherichia coli The 26 angstrom crysta structure of a complex BtuCDF reveals substantial conformational changes as compared with the previously reported structures of BtuCD and BtuF The lobes of BtuF are spread apart and B12 is displaced from the binding pocket The transmembrane BtuC subunits reveal two distinct conformations and the translocation pathway is closed to both sides of the membrane Electron paramagnetic resonance spectra of spinlabeled cysteine mutants reconstituted in proteoliposomes are consistent with the conformation of BtuCDF that was observed in the crystal structure A comparison with BtuCD and the homologous HI147O 71 protein suggests that the structure of BtuCDF may re ect a posttranslocation intermediate Multicolor SuperResolution Imaging with PhotoSwitchable Fluorescent Probes Science Vol 317 Issue 5845 17491753 21 September 2007 Mark Bates1 Bo Huang23 Graham T Dempsey4 Xiaowei Zhuang Recent advances in farfield optical nanoscopy have enabled uorescence imaging with a spatial resolution of 20 to 50 nanometers Multicolor superresolution imaging however remains a challenging task Here we introduce a family of photoswitchable uorescent probes and demonstrate multicolor stochastic optical reconstruction microscopy STORM Each probe consists of a photoswitchable quotreporterquot uorophore that can be cycled between uorescent and dark states and an quotactivatorquot that facilitates photoactivation of the reporter Combinatorial pairing of reporters and activators allows the creation of probes with many distinct colors Iterative colorspecific activation of sparse subsets of these probes allows their localization with nanometer accuracy enabling the construction of a superresolution STORM image Using this approach we demonstrate multicolor imaging of DNA model samples and mammalian cells with 20 to 30nanometer resolution This technique will facilitate direct visualization of molecular interactions at the nanometer scale Structures of the CCR5 N Terminus and of a TyrosineSulfated Antibody with HIV1 gp120 and CD4 Science Vol 317 Issue 5846 19301934 28 September 2007 Chih chin Huang1 Son N Lam 2 Priyamvada Acharya1 Min Tang1 Shi Hua Xiang3 Syed Shahzad ul Hussan2 Robyn L Stanfield4 James Robinson5 Joseph Sodroski3 Ian A Wilson4 Richard Wyatt1 Carole A Bewley2zT Peter D Kwong The CCR5 coreceptor binds to the HIV1 gp120 envelope glycoprotein and facilitates HIV1 entry into cells Its N terminus is tyrosinesulfated as are many antibodies that react with the coreceptor binding site on gp120 We applied nuclear magnetic resonance and crystallographic techniques to analyze the structure of the CCR5 N terminus and that of the tyrosinesulfated antibody 412d in complex with gp120 and CD4 The conformations of tyrosinesulfated regions of CCR5 amhelix and 412d extended loop are surprisingly different Nonetheless a critical sulfotyrosine on CCR5 and on 412d induces similar structural rearrangements in gp120 These results now provide a framework for understanding HIV1 interactions with the CCR5 N terminus during viral entry and define a conserved site on gp120 whose recognition of sulfotyrosine engenders posttranslational mimicry by the immune system PNAS Inhibitors of metabolism rescue cell death in Huntington39s disease models PNAS September 4 2007 vol 104 no 36 1452514530 Hemant Varma Richard Cheng Cindy Voisinei Anne C HartJr and Brent R Stockwell Huntington39s disease HD is a fatal inherited neurodegenerative disorder HD is caused by polyglutamine expansions in the huntingtin htt protein that result in neuronal loss and contribute to HD pathology The mechanisms of neuronal loss in HD are elusive and there is no therapy to alleviate HD To find small molecules that slow neuronal loss in HD we screened 1040 biologically active molecules to identify suppressors of cell death in a neuronal cell culture model of HD We found that inhibitors of mitochondrial function or glycolysis rescued cell death in this cell culture and in in vivo HD models These inhibitors prevented cell death by activating prosurvival ERK and AKT signaling but without altering cellular ATP levels ERK and AKT inhibition through the use of specific chemical inhibitors abrogated the rescue whereas their activation through the use of growth factors rescued cell death suggesting that this activation could explain the protective effect of metabolic inhibitors Both ERK and AKT signaling are disrupted in HD and activating these pathways is protective in several HD models Our results reveal a mechanism for activating prosurvival signaling that could be exploited for treating HD and possibly other neurodegenerative disorders Journal of the American Chemical Society A RhodamineBased Fluorescent Probe Containing a SeN Bond for Detecting Thiols and Its Application in Living Cells J Am Chem Soc 129 38 11666 11667 2007 Bo Tangl Yanlong Xing1 Ping Li 39 Ning Zhangl39 Fabiao Yu139 and Guiwen Yang U 4 i E c DIEquot IL 11025 kwssm 1 2 22 ltJ R CH3 H c 2 V H a lt 5 7 1 J Jet h 1 IL L R So N 0 39 N39 K 9pr 2 D 1 N39A EF 1 K n 5 ch Mash Here we report a new rhodaminebased uorescent probe containing a selenium nitrogen bond for detecting thiols based on the nucleophilic substitution of sulfhydryl The probe was successfully applied to the imaging of thiols in both HL7702 cells and HepG2 cells with high sensitivity and selectivity Carbon Dots for Multiphoton Bioimaging J Am Chem Soc 129 37 11318 11319 2007 Li Cao Xin Wang Mohammed J Meziani Fushen Lu Haifang Wang Pengju G Luo Yi Lin Barbara A Harruff L Monica Veca Davoy Murray Su Yuan Xie and Ya Ping Sun Carbon nanoparticles upon simple surface passivation exhibit bright photoluminescence Reported here is a new finding that these carbon dots are also strongly twophoton luminescent with pulsed laser excitation in the nearinfrared The experimentally measured twophoton absorption crosssections are comparable to those of the highperformance semiconductor quantum dots already available in the literature The twophoton luminescence microscopy imaging of human breast cancer cells with internalized carbon dots is demonstrated Detecting Binding Interactions Using Microarrays of Natural Product Extracts J Am Chem Soc 129 37 11346 11347 2007 Katja Schmitz3939 Stephen J Haggarty Olivia M McPherson Jon Clardy and Angela N Koehler mam f i Smallmolecule microarrays have been used to discover biologically active small molecules in collections of synthetic compounds Here we utilize a versatile isocyanate chemistry to immobilize extracts from microorganisms in a microarray format Specific bioactive small molecules are detected in crude extracts of Streptomyces hygroscopicus and the amount of specific to nonspecific binding of a protein to an immobilized compound on a microarray can be estimated These natural productextract microarrays NPEMs provide new tools for characterizing the metabolic products of organisms and for discovering biologically active small molecules from nature Direct Electrochemical Evaluation of Plasma Membrane Cholesterol in Live Mammalian Cells J Am Chem Soc 129 37 11352 11353 2007 Dechen J iang li Anando Devadoss3939J M Simona Palencszirj Danjun Fang Nicole M WhiteC Thomas J Kelley Jonathan D Smith and James D Burgess Cholesterol is a tightly regulated structural component of the cell plasma membrane Dysfunctional intracellular cholesterol transport machinery causes disease states with altered plasma membrane cholesterol This Communication reports microelectrode evaluation of plasma membrane cholesterol of single cells at physiological temperature Electrochemical data indicate that transport of intracellular cholesterol to the plasma membrane is active in an atherosclerotic macrophage model PhosphateMediated Arginine Insertion into Lipid Membranes and Pore Formation by a Cationic Membrane Peptide from SolidState NMR J Am Chem Soc 129 37 11438 11446 2007 Ming Tangl39 Alan J WaringJC and Mei Hong 13133 P dislan ces WK Am 5 Torojdarlpore oa a k I ma 5m 5 i o m m l 02 it quot0 V 7 m1 40 A 513 aw guammmum a phasnham 1 5 It mg 0 The insertion of charged amino acid residues into the hydrophobic part of lipid bilayers is energetically unfavorable yet found in many cationic membrane peptides and protein domains To understand the mechanism of this translocation we measured the 13C 31P distances for an Argrich hairpin antimicrobial peptide PG1 in the lipid membrane using solidstate NMR Four residues including two Arg39s scattered through the peptide were chosen for the distance measurements Surprisingly all residues show short distances to the lipid 31F 4065 A in anionic POPEPOPG membranes and 65 80 A in zwitterionic POPC membranes The shortest distance of 40 A found for a guanidinium C at the turn suggests NHOP hydrogen bond formation Torsion angle measurements of the two Arg39s quantitatively confirm that the peptide adopts a hairpin conformation in the lipid bilayer and gelphase 1H spin diffusion from water to the peptide indicates that PG1 remains transmembrane in the gel phase of the membrane For this transmembrane hairpin peptide to have short 13C31P distances for multiple residues in the molecule some phosphate groups must be embedded in the hydrophobic part of the membrane with the local 31F plane parallel to the 39strand This provides direct evidence for toroidal pores where some lipid molecules change their orientation to merge the two monolayers We propose that the driving force for this toroidal pore formation is guanidiniumphosphate complexation where the cationic Arg residues drag the anionic phosphate groups along as they insert into the hydrophobic part of the membrane This phosphatemediated translocation of guanidinium ions may underlie the activity of other Argrich antimocrobial peptides and may be common among cationic membrane proteins Paclitaxel Functionalized Gold Nanoparticles J Am Chem Soc 129 37 11653 11661 2007 Jacob D Gibson Bishnu P Khanal and Euene R Zubarev if E 39 1 Q m Equot 39 J Here we describe the first example of 2 nm gold nanoparticles Au NPs covalently functionalized with a chemotherapeutic drug paclitaxel The synthetic strategy involves the attachment of a exible hexaethylene glycol linker at the C 7 position of paclitaxel followed by coupling of the resulting linear analogue to phenolterminated gold nanocrystals The reaction proceeds under mild esterification conditions and yields the product with a high molecular weight while exhibiting an extremely low polydispersity index 102 relative to linear polystyrene standards TGA analysis of the hybrid nanoparticles reveals the content of the covalently attached organic shell as nearly 67 by weight which corresponds to 70 molecules of paclitaxel per 1 nanoparticle The presence of a paclitaxel shell with a high grafting density renders the product soluble in organic solvents and allows for detailed 1H NMR analysis and therefore definitive confirmation of its chemical structure Highresolution TEM was employed for direct visualization of the inorganic core of hybrid nanoparticles which were found to retain their average size shape and high crystallinity after multiple synthetic steps and purifications The interparticle distance substantially increases after the attachment of paclitaxel as revealed by lowmagnification TEM suggesting the presence of a larger organic shell The method described here demonstrates that organic molecules with exceedingly complex structures can be covalently attached to gold nanocrystals in a controlled manner and fully characterized by traditional analytical techniques In addition this approach gives a rare opportunity to prepare hybrid particles with a well defined amount of drug and offers a new alternative for the design of nanosized drug delivery systems RNA Probes 0f Steric Effects in Active Sites High Flexibility of HIV1 Reverse Transcriptase J Am Chem Soc 2007 129 35 10626 10627 Adam P Silverman and Eric T K001 43 L A 439 As part of viral replication the HIV1 reverse transcriptase HIVRT makes a DNA copy of the RNA genome of the virus It is a mutagenic polymerase which leads to the rapid development of resistance in patients being treated with antiviral drugs To study the mechanism by which this enzyme makes frequent errors we have developed and used a set of variably sized nonpolar uridine analogues rH rF rL rB in RNAs to probe its functional steric exibility in nucleotide incorporation Our kinetics studies show that the enzyme pairs all the analogues selectively with adenine with a preference for dichloro analogues However unlike highfidelity replicative DNA polymerases this reverse transcriptase shows little sensitivity to size increases beyond the optimum which gives evidence for unusually high steric exibility This suggests that at least part of the mutagenic behavior of the HIV1 virus is caused by active site exibility in its replicating enzyme Transcriptional Upregulation in Cells Mediated by a Small Molecule J Am Chem Soc 2007 129 35 10654 10655 Steven P Rowe Ryan J Casey Brian B Brennan Sara J Buhrlage and Anna K Mapp Activator artificial transcription factors molecules that seek out specific genes and up regulate their transcription are desirable as mechanistic tools and as potential therapeutic agents One challenge has been the identification of small moleculebased activator ATFs that function in cellular systems Here we demonstrate that an amphipathic isoxazolidine activates transcription up to 80fold in human cells when targeted to a specific promoter Analogous to natural transcriptional activators the function of the isoxazolidine appears to be independent of the DNAtargeting moiety suggesting that the molecule will be effective in a variety of contexts This is thus a critical step toward activator ATFs constructed from small molecule components De Novo Design of a SingleChain Diphenylporphyrin Metalloprotein J Am Chem Soc 2007 129 35 10732 10740 Gretchen M Bender139 Andreas LehmannJE Hongling Zou Hong Cheng H Christopher Fry Don Engel139 Michael J Therien J Kent Blasie i Heinrich Roder Jeffrey G Saven and William F DeGrado We describe the computational design of a singlechain fourhelix bundle that noncovalently selfassembles with fully synthetic nonnatural porphyrin cofactors With this strategy both the electronic structure of the cofactor as well as its protein environment may be varied to explore and modulate the functional and photophysical properties of the assembly Solution characterization NMR UV vis of the protein showed that it bound with high specificity to the desired cofactors suggesting that a uniquely structured protein and welldefined site had indeed been created This provides a genetically expressed singlechain protein scaffold that will allow highly facile exible and asymmetric variations to enable selective incorporation of different cofactors surfaceimmobilization and introduction of spectroscopic probes Biomimetic Interactions of Proteins with Functionalized Nanoparticles A Thermodynamic Study J Am Chem Soc 2007 129 35 10747 10753 Mrinmoy De Chang Cheng You Sudhanshu Srivastava and Vincent M Rotello Gold nanoparticles NPs functionalized with Lamino acidterminated monolayers provide an effective platform for the recognition of protein surfaces Isothermal titration calorimetry ITC was used to quantify the binding thermodynamics of these functional NPs with m chymotrypsin ChT histone and cytochrome c Cth The enthalpy and entropy changes for the complex formation depend upon the nanoparticle structure and the surface characteristics of the proteins eg distributions of charged and hydrophobic residues on the surface Enthalpyentropy compensation studies on these NPprotein systems indicate an excellent linear correlation between AH and TAS with a slope x of 107 and an intercept TASO of 352 kJ mol1 This behavior is closer to those of native proteinprotein systems cc 092 and TASO 411 kJ mol1 than other proteinligand and synthetic hostguest systems Engineering a Monomeric Miniature Protein J Am Chem Soc 2007 129 36 11024 11025 Abby M Hodges and Alanna Schepartz WA P135 VHF substitution prolim switch unfolded monomer aPIquot folded app nmssmw dimer folded momma The stability size and structure of the avian pancreatic polypeptide aPP has made it an ideal starting point for the design of miniature proteins capable of binding DNA and protein surfaces with exceptionally high affinity and specificity both in vitro and in mammalian cells and extracts Despite these attributes some miniature proteins based on the aPP selfassociate at micromolar concentrations into dimers or higher order aggregates Here we systematically isolate quantify and remove the two structural elements responsible for aPP dimerization and then install a new structural elementa quotproline switc quotthat singlehandedly repacks aPP39s signature fold The result is a monomeric and wellfolded miniature protein that should accelerate the in vitro and in vivo application of these molecules Fully Synthetic Carbohydrate HIV Antigens Designed 0n the Logic of the 2G12 Antibody J Am Chem Soc 2007 129 36 11042 11044 Isaac J Krauss Joseph G Joyce Adam C Finnefrock Hong C Song Vadim Y Dudkinj39 Xudong Genng J David Warren Michael Chastain John W Shiver and Samuel J Danishefsky mama new 9mm i 39ormallul39l BMW zmz gpm i llmlinn mnjugabn main Di and trivalent glycopeptide mimics of the HIV 2G12 epitope have been synthesized and evaluated for their comparative 2G12 binding characteristics The epitope mimics consist of a cyclic peptide scaffold unrelated to gp120 peptide sequences attached via aspartate linkages to two or three copies of the highmannose glycan Man9GlcNAc2 The synthesis has been achieved via highyielding double and triple Lansbury aspartylations of Man9GlcNAc2NH2 with peptides containing respectively two and three aspartate residues Conjugation of such constructs with an immunogenic carrier protein OMPC has been accomplished through the peptides cysteine sulfhydryl function and Biacore assays have shown that binding affinity for 2G12 increases with increasing valency Angewandte Chemie lonal steblllly of hayplns has been e a adley A M Wuek F nehe examined by replacing a backbone amide eeples mm mam No need in References The conformas kg s A4 P gmu by a thlcester see pc me e 7 7055 7055 Increased exlblllty causes a decrease ln the hahpln stahlhty without Changing 5 78 Thermodynamlc Analysis of iSheet the structure ofthe folded conformation Secondary Structure by Backbone and allows the Slablllty ofthe folded state Thloesler Exchange to be measuved under natwe condltlons without the need for reference com pounds for the fully unfolded and folded states 9 s 6 8 X shen L zhang x liangls v H lsnelecmc nmnte a 16m 7104710 9 Flucculatlnn Reversible Surface Switching of Nanagel pH lt A 8 pH gt 5 Z Triggeled by Bttemal Stimu lnside nut and back again A novel pH changes In the medium see pleture nanogel Composed oFtwo blueompatlble The pHdependem surface swuch ufthls components namely rhltosan and ethy 39 a e E 2 i 5 1 a e vs 2 3 a 3 a s Compasltlon and charge In response to ACS Chemical Biology The New Biomimetic Chemistry Arti cial Transcription Factors ACS Chem Biol 2 9 599 601 John T Koh and J ianfei Zheng ile many research programs have focused on the challenge of developing small molecules that can inhibit proteiniprotein interactions some researchers have taken the problem one step further by attempting to develop small molecules that mimic the essential features of an entire protein An area of particular interest has been in the eld of artificial transcription factors ATFs where the essential function of some transcription factors is to recruit and promote the assembly of a larger transcription complex leading to the expression of a gene of interest The goal of synthesizing small molecule TFs olds promise as a means to independently control the expression of genes such as those that are misregulated in cancer and disease Design of Cyclic Peptides That Bind Protein Surfaces with Antibody Like Affinity ACS Chem Biol 2 9 625 634 Steven W Millwardi Stephen Fiacco Ryan J Austin and Richard W Roberts There is a pressing need for new molecular tools to target protein surfaces with high af nity and specificity Here we describe cyclic messenger RNA display with a trillion 11 member covalent peptide macrocycle library Using this library we have designed a number of highaffinity redoxinsensitive cyclic peptides that target the signaling protein Gdil In addition to cyclization our library construction took advantage of an expanded genetic code utilizing nonsense suppression to insert Nmethylphenylalanine as a 21st amino acid The designed macrocycles exhibit several intriguing features First the core motif seen in all of the selected variants is the same and shares an identical context with respect to the macrocyclic scaffold consistent with the idea that selection simultaneously optimizes both the cyclization chemistry and the structural placement of the binding epitope Second detailed characterization of one molecule cyclic Gdi binding peptide cycGiBP demonstrates substantially enhanced proteolytic stability relative to that of the parent linear molecule Third and perhaps most important the cycGiBP peptide binds the target with very high affinity Ki z 21 nM similar to those of many of the best monoclonal antibodies and higher than that of the By heterodimer an endogenous Gdil ligand Overall the work provides a general route to design novel low molecularweight highaffinity ligands that target protein surfaces Chemistry and Biology Semisynthetic Murine Prion Protein Equipped with a GPI Anchor Mimic Incorporates into Cellular Membranes Volume 14 Issue 19 21 September 2007 Pages 9941006 Diana Olschewski Ralf Seidel Margit Miesbauer Angelika S Rambold Dieter Oesterhelt Konstanze F Winklhofer J org Tatzelt Martin Engelhard and Christian FW Becker Conversion of cellular prion protein PrPC into the pathological conformer PrPSc has been studied extensively by using recombinantly expressed PrP rPrP However due to inherent difficulties of expressing and purifying posttranslationally modified rPrP variants only a limited amount of data is available for membraneassociated PrP and its behavior in vitro and in vivo Here we present an alternative route to access lipidated mouse rPrP rPrPPalm via two semisynthetic strategies These rPrP variants studied by a variety of in vitro methods exhibited a high affinity for liposomes and a lower tendency for aggregation than rPrP In vivo studies demonstrated that doublelipidated rPrP is efficiently taken up into the membranes of mouse neuronal and human epithelial kidney cells These latter results enable experiments on the cellular level to elucidate the mechanism and site of PrPPrPSc conversion The Biosynthesis of TeicoplaninType Glycopeptide Antibiotics Assignment of P450 MonoOxygenases to Side Chain Cyclizations 0f Glycopeptide A47934 Volume 14 Issue 19 September 2007 Pages 10781089 Bianka Hadatsch Diane Butz Timo Schmiederer Julia Steudle Wolfgang Wohlleben Roderich Siissmuth and Evi Stegmann Streptomyces toyocaensis produces A47934 a teicoplaninlike typeIV glycopeptide with antibiotic activity against methicillinresistant Staphylococcus aureus A47934 differs from the typeI vancomycin glycopeptides which possess a tricyclic peptide backbone by the presence of an additional ring closure between the aromatic amino acids 1 and 3 To elucidate the order of crosslinking reactions P450 monooxygenase inactivation mutants AstaF AstaG AstaH and AstaJ of the A47934 producer were generated and the accumulated intermediates were analyzed Thus the formation of each crosslink could unambiguously be assigned to a specific oxygenase The structure of the released intermediates from the wildtype nonribosomal peptide synthetase assembly line facilitated the determination of the cyclization order Unexpectedly the additional ring closure in A47934 catalyzed by StaG is the second oxygenase reaction Chemical Biology and Drug Design Structure activity Relationships of Amyloid Betaaggregation Inhibitors Based on Curcumin In uence of Linker Length and Flexibility Chem Biol Drug Des 2007 70 206 215 Ashley A Reinke and Jason E Gestwicki Selfassembly of amyloid beta into fibrillar plaques is characteristic of Alzheimer s disease and oligomers of this peptide are believed to be involved in neurodegeneration Natural organic dyes such as congo red and curcumin bind tightly to amyloid beta and at higher concentrations block its selfassembly The ability of these molecules to prevent amyloid accumulation has generated interest in understanding which of their structural features contribute to inhibitory potency In general amyloid beta ligands tend to be at planar molecules with substituted aromatic end groups however a comprehensive structure activity study has not been reported To better understand these ligands we surveyed the effect of three prominent features on inhibition of amyloid aggregation the presence of two aromatic end groups the substitution pattern of these aromatics and the length and exibility of the linker region We found that modification of any one of the modules has profound effects on activity Further we report that the optimal length of the linker lies within a surprisingly narrow regime 6 19 A These results offer insight into the key chemical features required for inhibiting amyloid beta aggregation In turn these findings help define the nature of the docking site for small molecules on the amyloid beta surface Suppression of Type 1 Diabetes in NOD Mice by Bifunctional Peptide Inhibitor Modulation of the Immunological Synapse Formation Chem Biol Drug Des 2007 70 227 236 Joseph S Murray12 Sabah Oney2 Jennifer E Page Angela Kratochvil Stava Yongbo Hu1 Irwan T Makagiansarl John C Brown Naoki Kobayashil and Teruna J Siahaan The aim of this work was to design and utilize a bifunctional peptide inhibitor called glutamic acid decarboxylase bifunctional peptide inhibitor to suppress the progression 13 of type 1 diabetes in nonobese diabetic mice The hypothesis is that glutamic acid decarboxylase bifunctional peptide inhibitor binds simultaneously to major histocompatibility complexII and intercellular adhesion molecule type 1 on antigen presenting cell and inhibits the immunological synapse formation during Tcell antigenpresenting cell interactions Glutamic acid decarboxylase bifunctional peptide inhibitor was composed of a major epitope of the type 1 diabetesassociated antigen glutamic acid decarboxylase 65 kDa covalently linked to a peptide derived from CD11a of lymphocyte functionassociated antigen1 The suppression of insulitis and type 1 diabetes was evaluated using nonobese diabetic and nonobese diabetic severe combined immunodeficiency mice Glutamic acid decarboxylase bifunctional peptide inhibitor had the capacity to suppress invasive insulitis in nonobese diabetic mice CD4 Tcells isolated from glutamic acid decarboxylase bifunctional peptide inhibitor treated mice also suppressed insulitis and hyperglycemia when transferred with diabetogenic nonobese diabetic spleen cells into nonobese diabetic severe combined immunodeficiency recipients As predicted the glutamic acid decarboxylase bifunctional peptide inhibitor crosslinked a significant fraction of major histocompatibility complex classII molecules to intercellular adhesion molecule type 1 molecules on the surface of live antigenpresenting cell Intravenous injection of the glutamic acid decarboxylase bifunctional peptide inhibitor elicited interleukin4 producing Tcells in nonobese diabetic mice primed against the glutamic acid decarboxylaseepitope peptide Together the results indicate that glutamic acid decarboxylase bifunctional peptide inhibitor induces interleukin4producing regulatory cells but does not expand the glutamic acid decarboxylasespecific Th2 population Given that Th2 effector cells can cause pathology the glutamic acid decarboxylase bifunctional peptide inhibitor may represent a novel mechanism to induce interleukin4 without Th2associated pathology Organic Letters New Sensitive Fluorophores for Selective DNA Detection Org Lett 9 20 4001 4004 2007 Brenno A D Netofl Alexandre A M Lapisji Fabiana S Mancilha Igor B Vasconcelosji39 Caroline Thum1 Luiz A BassoT Diogenes S Santos139 and J airton Dupont angeHansfer DNA binduig il l 7 iih 139 ML 53 ST 395 elecaron electron acceplm l M 47 Disubstituted benzothiadiazoles containing 1 rylethynyl and 4methoxyphenyl groups are selective photoluminescent quotlight upquot probes to duplex DNA with unprecedented sensibility in both spectrophotometric and spectro uorimetric measurements Synthesis of StimuliResponsive Cyclodextrin Derivatives and Their Inclusion Ability Control by Ring Opening and Closing Reactions Org Lett 9 20 3909 3912 2007 Akira Kikuzawa Toshiyuki Kida and Mitsuru Akashi RoanLian bli nln Novel stimuliresponsive cyclodextrins CDs in which a disulfide unit was inserted into the rings of permethylated x and li CDs were synthesized Their inclusion ability was controlled by the opening and closing of the ring based on dithioldisulfide interconversions Chmielewski Group Literature Abstracts February 2007 Contributing Editors Stefan Hershberger Science Marcos Pires Nature and Nature subdivisions Brandon Gaddis Iris Geisler JACS J ee Yeon Lee PNAS Dawn Ernenwein Chem ampBio Chem Biol ampDrug Design Dave Przybyla Angewandte Chemie Hilda Namanja ACS Chemical Biology Nicole O Neil Org Lett Nature Enantioselective halocyclization of polyprenoids induced by nucleophilic phosphoramidites Nature 445 900903 22 February 2007 Akira Sakakura1 Atsushi Ukai1 and Kazuaki Ishihara1 Polycyclic bioactive natural products that contain halogen atoms have been isolated r m a number of different marine organisms1 The biosynthesis of these natural products appears to be initiated by an electrophilic halogenation reaction at a carbon7 carbon double bond2 3 4 via a mechanism that is similar to a protoninduced olefin polycyclization5 6 7 8 Enzymes such as haloperoxidases generate an electrophilic halonium ion or its equivalent which reacts with the terminal carbonicarbon double bond of the polyprenoid enantioselectively inducing a cyclization reaction that produces a halogenated polycyclic terpenoid Use of an enantioselective halocyclization reaction is one possible way to chemically synthesize these halogenated cyclic terpenoids althou h several brominated cyclic terpenoids have been synthesized via a diastereoselective halocyclization reaction that uses stoichiometric quantities of a brominating reagent9 10 11 12 e enantioselective halocyclization of isoprenoids induced by a chiral promoter has not yet been reported Here we report the enantioselective halocyclization of simple polyprenoids using a nucleophilic promoter Achiral nucleophilic phosphorus compounds are able to promote the diastereoselective halocyclization reaction to give a halogenated cyclic product in excellent yields Moreover chiral phosphoramidites promote the enantioselective halocyclization of simple polyprenoids with N iodosuccinimide to give iodinated cyclic products in up to 99 enantiomeric excess and diastereomeric excess To the best of our knowledge this is the rst successful example 1 Nature Chemical Biology Bioinformatic discovery of novel bioactive peptides Nature Chemical Biology 3 108112 2007 Richard J Edwards124 Niamh Moran14 Marc Devocelle3 Aoife Kiernan1 Gerardene Meade1 William Signac1 Martina Foy1 Stephen D E Park1 Eimear Dunne1 Dermot Kenny1 and Denis C Shields v Short synthetic oligopeptides based on regions of human proteins that encompass functional motifs are versatile reagents for understanding protein signaling and interactions They can either mimic or inhibit the parent protein39s activity1 2 3 4 and have been used in drug development5 Peptide studies typically either derive peptides from a single identified protein or at the other extreme screen random combinatorial peptides4 6 often without knowledge of the signaling pathways targeted Our objective was to determine whether rational bioinformatic design of oligopeptides specifically targeted to potentially signalingrich juxtamembrane regions could identify modulators of human platelet function Highthroughput in vitro platelet function assays of palmitylated cellpermeable oligopeptides corresponding to these regions identified many agonists and antagonists of platelet function Many bioactive peptides were from adhesion molecules including a specific CD226derived inhibitor of insideout platelet signaling Systematic screens of this nature are highly efficient tools for discovering short signaling motifs in molecular signaling pathways Nature Methods Smallmolecule mimics of an alphahelix for ef cient transport of proteins into cells Nature Methods 4 153 159 2007 Masahiro Okuyama1 6 Heike Laman2 5 6 Sarah R Kingsbury3 6 Cristina Visintin1 Elisabetta Leo3 Kathryn Leigh Eward3 5 Kai Stoeber3 4 Chris Boshoff2 Gareth H Williams3 4 amp David L Selwood We designed and synthesized smallmolecule mimics of an alphahelical peptide protein transduction domain PTD These smallmolecule carriers which we termed SMoCs are easily coupled to biomolecules and efficiently deliver dye molecules and recombinant proteins into a variety of cell types We designed the SMoCs using molecular modeling techniques As an example of a protein cargo we applied this new technology to the internalization of the DNA replication licensing repressor geminin in vitro providing evidence that extracellularly delivered SMoC geminin can have an antiproliferative effect on human cancer cells Uptake of SMoC geminin was inhibited at 4 C and by chlorpromazine a compound that induces misassembly of clathrincoated pits at the cell surface Thus the mechanism of uptake is likely to be clathrinmediated endocytosis Nature Nanotechnology Cellular uptake of functionalized carbon nanotubes is independent of functional group and cell type Nature Nanotechnology 2 108 113 2006 Kostas Kostarelos1 Lara Lacerda1 Giorgia Pastorin3 Wei Wu3 S bastien Wieckowski3 Jacqueline Luangsivilay3 Sylvie Godefroy3 Davide Pantarotto23 J ean Paul Briand3 Sylviane Muller3 Maurizio Prato3 and Alberto Bianco The development of nanomaterials for biomedical and biotechnological applications is an area of research that holds great promise and intense interest1 and carbonbased nanostructures in particular such as carbon nanotubes CNTs are attracting an increasing level of attention2 3 One of the key advantages that CNTs offer is the possibility of effectively crossing biological barriers which would allow their use in the delivery of therapeutically active molecules Our laboratories have been investigating the use of CNTs in biomedical applications and in particular as nanovectors for therapeutic agent delivery4 5 6 7 8 The interaction between cells and CNTs is a critical issue that will determine any future biological application of such structures Here we show that various types of functionalized carbon nanotubes fCNTs exhibit a capacity to be taken up by a wide range of cells and can intracellularly traffic through different cellular barriers Science Apoptosis Initiated When BH3 Ligands Engage Multiple Bel2 Homologs Not Bax or Bak Science Vol 315 Issue 5813 856859 9 February 2007 Simon N Willis1 Jamie I Fletcher1 Thomas Kaufmann1 Mark F van Delft12 Lin Chen1 Peter E Czabotar1 Helen Ierino1 Erinna F Lee12 W Douglas Fairlie1 Philippe Bouillet1 Andreas Strasser1 Ruth M Kluck1 Jerry M Adams1 David C S Huang A central issue in the regulation of apoptosis by the Bcl2 family is whether its BH3only members initiate apoptosis by directly binding to the essential celldeath mediators Bax and Bak or whether they can act indirectly by engaging their prosurvival Bcl2 like relatives Contrary to the directactivation model we show that Bax and Bak can mediate apoptosis without discernable association with the putative BH3only activators Bim Bid and Puma even in cells with no Bim or Bid and reduced Puma Our results indicate that BH3only proteins induce apoptosis at least primarily by engaging the multiple prosurvival relatives guarding Bax and Bak PNAS Understanding the nanoparticle protein corona using methods to quantify exchange rates and af nities of proteins for nanoparticles PNAS February 13 2007 vol 104 no 7 20502055 Tommy Cedervall Iseult Lynch Stina Lindman Tord Berggard Eva Thulin Hanna Nilsson Kenneth A Dawsonand Sara Linse Due to their small size nanoparticles have distinct properties compared with the bulk form of the same materials These properties are rapidly revolutionizing many areas of medicine and technology Despite the remarkable speed of development of nanoscience relatively little is known about the interaction of nanoscale objects with living systems In a biological uid proteins associate with nanoparticles and the amount and presentation of the proteins on the surface of the particles leads to an in vivo response Proteins compete for the nanoparticle quotsurfacequot leading to a protein quotcoronaquot that largely defines the biological identity of the particle Thus knowledge of rates affinities and stoichiometries of protein association with and dissociation from nanoparticles is important for understanding the nature of the particle surface seen by the functional machinery of cells Here we develop approaches to study these parameters and apply them to plasma and simple model systems albumin and fibrinogen A series of copolymer nanoparticles are used with variation of size and composition hydrophobicity We show that isothermal titration calorimetry is suitable for studying the affinity and stoichiometry of protein binding to nanoparticles We determine the rates of protein association and dissociation using surface plasmon resonance technology with nanoparticles that are thiollinked to gold and through size exclusion chromatography of protein nanoparticle mixtures This method is less perturbing than centrifugation and is developed into a systematic methodology to isolate nanoparticle associated proteins The kinetic and equilibrium binding properties depend on protein identity as well as particle surface characteristics and size Journal of the American Chemical Society Ambient Temperature Synthesis of High Enantiopurity N Protected Peptidyl Ketones by Peptidyl Thiol EsterBoronic Acid CrossCoupling J Am Chem Soc 2007 129 5 1132 1140 Hao Yang Hao Li Rudiger Wittenberg139 Masahiro Egi1i Wenwei Huang and Lanny S Liebeskind u o l cm waiJLSN mom z CMHN HLRZ a R mom d arm no racsmizahun Ifl DE i l39 5 ESLAman acid thiol esters derived from Nprotected mono di and tripeptides couple with aryl u electronrich heteroaryl or alkenyl boronic acids in the presence of stoichiometric Cu1 thiophene2carboxylate and catalytic Pd2dba3triethylphosphite to generate the corresponding Nprotected peptidyl ketones in goodtoexcellent yields and in high enantiopurity Triethylphosphite plays a key role as a supporting ligand by mitigating an undesired palladiumcatalyzed decarbonylation elimination of the 3 amino thiol esters The peptidyl ketone synthesis proceeds at room temperature under nonbasic conditions and demonstrates a high tolerance to functionality Discovery of Chemical Reactions through Multidimensional Screening J Am Chem Soc 2007 129 5 1413 1419 Aaron B Beeler Shun Su Chris A Singleton and John A Porco Jr rinll llnlion I quot nite 3940 39 when a anma New 2 o mp we m cm HE uu l i n n ua rm Multidimensional reaction screening of orthoalkynyl benzaldehydes with a variety of catalysts and reaction partners was conducted in an effort to identify new chemical reactions Reactions affording unique products were selected for investigation of preliminary scope and limitations minim Quantitative Evaluation of the Relative Cell Permeability of Peptoids and Peptides J Am Chem Soc 2007 129 6 1508 1509 YongUk Kwon and Thomas Kodadek fig I C UKquot 11 u cu l l L H gt7 gin123 0 SQex CO Pepmids39l epndes can mmmm We evaluated quantitatively the relative cell permeability of peptoids and peptides using a cellbased reporter genebased assay Generally peptoids were much more cell permeable than the corresponding peptides though the difference decreased with increasing length These results suggest that peptoids may be useful reagents for manipulating the activities of intracellular proteins Controlling Multiple Fluorescent Signal Output in Cyclic Peptide Based Supramolecular Systems J Am Chem Soc 2007 129 6 1653 1657 Roberto J Breaj M Eugenio Vazquezj Manuel Mosquerali Luis Castedo39l and Juan R Granja 33 E s34 mm 5 mg a Fag gmgjl g uwf g g A multicomponent equilibrium network based on selfassembling mF cyclic peptides with controlled uorescence output is described The network takes advantage of the large association constant of mixcyclic peptides and the controlled formation homo and heterodimers making use for the first time of excimer FRET effects in conjunction for studying complex interaction networks In addition we study the Dapoxylpyrene FRET pair for the first time DNAEncoded Antibody Libraries A Uni ed Platform for Multiplexed Cell Sorting and Detection of Genes and Proteins J Am Chem Soc 129 7 1959 1967 2007 1 x x a ml it quotHEmm umnmme quotI Whether for pathological examination or for fundamental biology studies different classes of biomaterials and biomolecules are each measured from a different region of a typically heterogeneous tissue sample thus introducing unavoidable sources of noise that are hard to quantitate We describe the method of DNAencoded antibody libraries DEAL for spatially multiplexed detection of ssDNAs and proteins as well as for cell sorting all on the same diagnostic platform DEAL is based upon the coupling of ssDNA oligomers onto antibodies which are then combined with the biological sample of interest Spotted DNA arrays which are found to inhibit biofouling are utilized to spatially stratify the biomolecules or cells of interest We demonstrate the DEAL technique for 1 the rapid detection of multiple proteins within a single micro uidic channel and with the additional step of electroless amplification of goldnanoparticle labeled secondary antibodies we establish a detection limit of 10 fM for the protein IL 2 150 times more sensitive than the analogue ELISA 2 the multiplexed onchip sorting of both immortalized cell lines and primary immune cells with an efficiency that exceeds surfaceconfined panning approaches and 3 the codetection of ssDNAs proteins and cell populations on the same platform CollagenRelated Peptides SelfAssembly of Short Single Strands into a Functional Biomaterial of Micrometer Scale J Am Chem Soc 129 8 2202 2203 2007 Mabel A CejasJ William A KinneyT Cailin Chen1 Gregory C Leof Brett A Tounge1 a Jeremy G Vinter 13 Pratik P J oshi and Bruce E Maryanoff g s maanw 9na cwcnnlwnw quotW F HU We have designed synthesized and characterized a short 32mer 8nm single stranded collagenrelated peptide CRP 1a which forms triplehelical building blocks that selfassemble into large composite fibrils by strictly noncovalent means Computational analysis suggested that the installation of complementary aromatic n stacking recognition elements at the N and C termini of Gly ProHyp10 would facilitate the headtotail assembly of triplehelical subunits Our CD 1H NMR DLS and TEM results for 1a support the formation of such triplehelical supramolecular structures Consistent with selfassembly into micrometersize composite fibrils 1a induced the aggregation of human platelets with nearly the same potency as native Type I collagen The aromaticaromatic recognition motif employed in this study provides a straightforward approach to collagenmimetics and has important implications for the design of triplehelical building blocks that can spontaneously oligomerize into functional fibrillar structures SelfAssembled Architectures from Biohybrid Triblock Copolymers J Am Chem Soc 129 8 2327 2332 2007 Irene C Reynhout J eroen J L M Cornelissen and Roeland J M Nolte 1quot The synthesis and selfassembly behavior of biohybrid ABC triblock copolymers consisting of a synthetic diblock polystyrenebpolyethylene glycol PSmbPEG113 where m is varied and a hemeprotein myoglobin Mb or horse radish peroxidase HRP is described The synthetic diblock copolymer is first functionalized with the heme cofactor and subsequently reconstituted with the apoprotein or the apoenzyme to yield the proteincontaining ABC triblock copolymer The obtained amphiphilic block copolymers selfassemble in aqueous solution into a large variety of aggregate structures Depending on the protein and the polystyrene block length micellar rods vesicles toroids figure eight structures octopus structures and spheres with a lamellar surface are formed Angewandte Chemie ic NA block copolymers Torin sphe rical rnicelles in solution They can be into mdllke niicelles by r lt g E E a a E glued toge her by hydrophobic interactions ohhe organic polymer see ictureThatem plate determines the length ufihe rodli aggregates ke Stringing them al orig The pores ota mesopomus silica particle werenlled With ac 3 0 ti o 5 at 2 cl 9 rii E E PEl chains at pH l l At pH 5 5 guest molecules can be released irorn the pores oFihe particle by reversible dethreading orthe CD5 mm the PEl chains ii w e a t 3 no A Hydrophlllc Hydrbphabto AuNF39s PEO e pMAW Aii NPs domain Gamaquot Likes anracl Sitespeei39f ic vecogmtion of hi gold nanoparlicles Au NPs was the na phase separated su o studied The hydrophilic and hydrophobic PEOmsb P n m PEO poly thy Au hips were found to selectively sserri ene oxld A1 polym thacrylate itli ezobenzene based liquid crystalline sidelthain by hydrophilic and hydropho Nol a hirdi no a plane perhaps a superatoiri The t eon superamm has lErS with a certain element sttticture On the basis ofstruetursl datathe question of daSSlrIEEKIOD lh le 39um lureshowsthe 5 p2 and ligandbearing Ga atoms in lhomic cluslu Transforming micelle structure Amphi DNA Black Copolyniers phil D K Ding F E Alemdaroglu M aorsch R Berger A HerrrriannT 71172 1175 Engineering the Stmcmral Properties of DN alcck Copolymer Micelles by Molecular Recognition Supramuleculal chemistry C Park K 0h SC Lee c Kim 1455 1457 Controlled Release of Guest Molecules from Mesoporous Silica Particles Based on a pHResponsive Polypseudomtaxane Motif Cold Nunnpnniclex Watanabee R Fujiwara M Hada v Okazaki T lyoda 1120 1113 SiteSpeci c Recognition of Nanophase Separated Surfaces of Amphiphllic Block Copolyrners by Hydrophilic and Hydrophobic Gold Natioperticles Cluster Compounds 1 Hartig A Sl39aiZer P Hausa H Schnockelk 7 165871662 A Motalloid caumlstMegle cluster The Jellium Model Put to Test 1dmur1a5 that amam phraan gmups far in O 1 1dmgarr D IE mm ML Buwm L E ScuttTStmv K Buhmcrc OH bnramd m nd ultasy1mmms F ThumaSD D AUunP R Lurkman in 1 and 1 be 1 U l M Mum K H Thumpsun quot0 N mg smsvum Rphzny4rhydmxyr 7171671713 A pheny1c1yms1dasu remuvai ufthc avr CumbaungA zhmmrr s Disease mm am mm p E Mumrmzmm Mulcw as Dmgncd m aspmaHy cuppcvand zmc m m 1mm Mum Passwahun mm mulcrulus am pamnua1 prudmgs furrmarmnm uineumde an vauvu disr cases1nud1ng mmsmws 11152352 ACS Chemical Biology The 3D Structure of Protein Phosphatase 2A New Insights into a Ubiquitous Regulator of Cell Signaling ACS Chem Biol 2 2 997103 Marc Mumby Protein phosphatase 2A PPZA is a serinethreonine phosphatase implicated in cancer Three new crystal structures of PP2A show how it interacts with inhibitory toxins and with one of its regulatory subunits The structures also explain how speci c site mutations may lead to cancer and suggest a novel role for PPZA methylation in the formation of PP2A holoenzymes Selective Tumor Cell Targeting Using LowAf nity Multivalent Interactions ACS Chem Biol 2 2 1197127 Coby B Carlsont t Patricia Moweryi Robert M Owenf Emily C Dykhuizen r and Laura L Kiessling This report highlights the advantages of lowaffinity multivalent interactions to recognize one ce type over another Our goal was to evise a s ra egy o mediate selective killing of tumor cells which are often distinguished from normal cells by their higher levels of particular cell surface rece t s T s whether multivalent interactions could lead to highly speci c cell targeting we used a chemically synthesized smallmolecule ligand composed of two distinct motifs 1 an ArgGlyAsp RGD peptidomimetic that binds tightly Kd 1079 M to dv g integrins and 2 the galactosyld173galactose ElGal epitope which is recognized by human antid galactosyl antibodies antiGal Importantly antiGal binding requires a multivalent presentation of carbohydrate residues antiGal antibodies interact weakly with the monovalent oligosaccharide Kd 1075 M but bind tightly Kd 10711 M to multivalent displays of dGal epitopes Such a display is generated when the bifunctional conjugate decorates a cell possessing a high level of dv g integrin the resulting cell surface which presents many dGal epitopes can recruit antiGal thereby 10 triggering complementmediated lysis Only those cells with high levels of the integrin receptor are killed In contrast doxorubicin tethered to the RGDbased ligand affords indiscriminate cell death These results highlight the advantages of exploiting the type of the multivalent recognition processes used by physiological systems to discriminate between cells The selectivity of this strategy is superior to traditional abiotic high affinity targeting methods Our results have implications for the treatment of cancer and other diseases characterized by the presence of deleterious cells Chemistry and Biology Hydrophobic Amino Acid and SingleAtom Substitutions Increase DNA Polymerase Selectivity Volume 14 Issue 2 February 2007 Pages 185194 Nicolas Z Rudinger Ramon Kranaster and Andreas Marx DNA polymerase fidelity is of immense biological importance due to the fundamental requirement for accurate DNA synthesis in both replicative and repair processes Subtle hydrogenbonding networks between DNA polymerases and their primertemplate substrates are believed to have impact on DNA polymerase selectivity We show that deleting defined interactions of that kind by rationally designed hydrophobic substitution mutations can result in a more selective enzyme Furthermore a single atom replacement within the DNA substrate through chemical modification which leads to an altered acceptor potential and steric demand of the DNA substrate further increased the selectivity of the developed systems Accordingly this study about the impact of hydrophobic alterations on DNA polymerase selectivity enzyme and substrate wise further highlights the relevance of shape complementary and polar interactions on DNA polymerase selectivity A HighThroughput Screen for Synthetic Riboswitches Reveals Mechanistic Insights into Their Function Volume 14 Issue 2 February 2007 Pages 173184 Sean A Lynch Shawn K Desai Hari Krishna Sajja and Justin P Gallivan Riboswitches are RNAbased genetic control elements that regulate gene expression in a liganddependent fashion without the need for proteins The ability to create synthetic riboswitches that control gene expression in response to any desired smallmolecule ligand will enable the development of sensitive genetic screens that can detect the presence of small molecules as well as designer genetic control elements to conditionally modulate cellular behavior Herein we present an automated high throughput screening method that identifies synthetic riboswitches that display extremely low background levels of gene expression in the absence of the desired ligand and robust increases in expression in its presence Mechanistic studies reveal how these riboswitches function and suggest design principles for creating new synthetic riboswitches We anticipate that the screening method and design principles will be generally useful for creating functional synthetic ribosvvitches Chemical Biology and Drug Design Improved Acylation Method Enables Efficient Delivery of Functional Palmitoylated Cystatin into Epithelial Cells Chem Biol Drug Des 2007 69 124 131 Nina Kocvevar Natasva Obermajer Borut Strukelj J anko Kos and Samo Kreft The effective delivery of therapeutic proteins to the site of action is of great importance in achieving an effective therapy Due to hydrophilicity proteins are generally poorly transported across biological membranes Chemical acylation represents one of the basic methods for improving their membrane permeability A novel method for acylation is presented based on the formation of palmitoylchloride dispersion in aqueous acetonitrile solution using chicken cystatin as a model protein We examined the effects of palmitoylchloridecystatin molar ratio reaction pH and introduction of successive palmitoylation cycles on the protein modification degree The reaction products were analysed by capillary electrophoresis and SDSPAGE and the in Vitro inhibitory activity was determined by NbenzoyldlarginineBnaphthylamide assay Using cell culturebased assays we examined the transport properties of unmodified and palmitoylated cystatin its efficiency to inhibit intracellular enzymes and its cytotoxicity We demonstrated that palmitoylated cystatin rapidly internalized into the cell and caused a complete loss of cathepsin B activity In contrast the unmodified control cystatin was unable to inhibit the intracellular enzymes These results strongly suggest protein palmitoylation to be a very effective strategy for improving cell internalization Organic Letters Selective Recognition of Tryptophan through Inhibition of Intramolecular ChargeTransfer Interactions in an Aqueous Medium Org Lett 9 3 417 420 2007 Mahesh Hariharan Suneesh C Karunakaran and Danaboyina Ramaiah A novel donoracceptor conjugate 1 was synthesized and its interactions with various amino acids have been investigated as compared to the model system 2 The conjugate 1 unusually forms an intramolecular chargetransfer complex in the aqueous medium and undergoes selective binding interactions with tryptophan The uniqueness of this system is that it selectively recognizes tryptophan among all other amino acids and involves synergistic effects of n stacking electrostatic and donoracceptor interactions Pro ling of Glycosidase Activities Using CoumarinConjugated Glycoside Cocktails Org Lett 9 4 619 622 2007 Sungjin Park and Injae Shin H if 1 1r 1 E Glycosmases fir ll i llng rlu39Lr L Glycosidases are a large subgroup of carbohydrateprocessing enzymes that hydrolytically cleave the glycosidic bond Glycans formed by the action of glycosidases are involved in various biological processes Genetic abnormalities in glycosidases are associated with inherited diseases Thus characterization of the catalytic activities of glycosidases is of great importance Herein we describe a simple and rapid approach for determining glycosidase activity profiles using coumarinconjugated glycoside cocktails Glycos Ida cocktails all I ilillill i39 i ll Selective Desulfurization of Cysteine in the Presence of CysAcm in Polypeptides Obtained by Native Chemical Ligation Org Lett 9141 682 690 2002 Brad L Pentelute and Stephen B H Kent leavc Cyl W Name Chenmal nnnjmnm Mac s M Dmu lrunmuon mam mm Increased versatility for the synthesis of proteins and peptides by native chemical ligation requires the ability to ligate at positions other than Cys Here we report that Raney nickel can be used under standard conditions for the selective desulfurization of Cys in the presence of CysAcm This simple and practical tactic enables the more common Xaa Ala junctions to be used as ligation sites for the chemical synthesis of Cys containing peptides and proteins Precision Agriculture Pro tability Review by Dayton Lambert amp J LowenbergDeBoer Sitespecific Management Center School of Agriculture Purdue University SSMCagadpurdueedu 15 Sept 2000 Soil Teq a subsidiary of the Ag Chem Corporation funded this literature review All responsibility for the contents is the sole responsibility of the authors Please inform the authors if any document has been misunderstood or misrepresented LambertDageconpurdueedu or LowenbergDeBoerageconpurdueedu Also please inform them of any omitted studies A full citation is important in allowing them to track down an omitted study an electronic or hard copy is very helpful Copyright 2000 by J LowenbergDeBoer and Alan Hallman All rights reserved Readers may make verbatim copies of this document for noncommercial purposes by any means provided that this copyright notice appears on all such copies PRECISION AGRICULTURE PROFITABILITY REVIEW EXECUTIVE SUMMARY Sitespeci c management is intuitively appealing to many producers and agribusiness people but intuitively appealing ideas are not always pro table The objective of this report is to summarize and organize the publicly available studies of the pro tability of precision agriculture Sources were refereed articles from scienti c journals or proceedings 86 and non technical or nonrefereed magazines and monographs specializing in agribusiness services 14 Scienti c refereed journals were categorized as reports that employed the scienti c method to answer research questions 67 or those that described general aspects of PA 33 The research questions included both the potential pro tability and the adoption process of PA within the agricultural community including dealerships and producers Popular magazines comprised 75 of the nonscienti c materials reviewed The remaining 25 of nonscienti c materials included documents that described PA generalities Of the 108 studies that reported economic gures 63 indicated positive net returns for a given PA technology while 11 indicated negative returns Table 5 There were 27 articles indicating mixed results 26 For all PA technology combinations identi ed over 50 of the studies reported positive bene ts except for VRTyield monitor systems Table 5 About 60 of the studies of N or NPK VRT systems reported pro ts Of the 63 documents reporting bene ts authored by economists 73 reported positive bene ts from PA 16 reported mixed results and 11 negative results Table 6 Of the nine documents with agribusiness authors reporting bene ts twothirds 66 of these articles reported positive results from PA while two articles 22 reported mixed results Only one individual employed by the agribusiness sector reported negative returns In terms of positive bene ts economists and agribusiness authors seem to be coming to be coming to the same conclusions The percentage of documents showing positive results was only slightly lower for studies using eld trial data than for those which used response functions or simulation to estimate yield Table 6 Positive results were reported for 60 of response functions studies 67 of eld trial studies and 75 of crop growth simulation studies Unsubstantiated studies showed about the same percentage of positive results as those using partial budgets Table 6 About 68 of the unsubstantiated studies showed positive results and 64 for the partial budgets When all the studies are categorized by crop corn soybean and sugar beet studies showed positive pro ts in over two thirds of cases Table 7 Only 20 of the studies on wheat showed pro ts and in another 20 results were mixed INTRODUCTION ANALYSIS DESCRIPTION OF STUDIES REPORTED BENEFITS CONCLUSIONS REFERENCE SECTION ANNOTATED BIBLIOGRAPHY 22 23 171 39SWELLSAS NOIlVOHddV HHZHILHHE39SED CLNV HOLINOW CHEHA39SED EO SISATVNV 139C108 WILHVE 3983 HTEWL quot 39SWELLSAS SdD CLNV HEDIHVW WVOE WOHE SNHHJHH EO NOSIHVCEWOO 39LZ HTEWL SHOHOWCI Mimomgv NOISIOERH NOWOO EO SNOLLVNIEEWOO lNEHHEEIG HOE SHEDHGOHE Ol SNH lEH WM 3993 HTEWL quotquot quot 39SdIHSHHTVHG A8 C1E1HE1EEO SEDIAHHS SHOIHVA EO EHOVSLSOO 39SZ HTEWL 39 SHIDELLVHLS DNIGHHS HlVH HTEWIHVA WOHE SNH lEH C1E11HOc1E1H 39VZ HTEWL L01 quotquotquotquotquotquotquotquot 39 39DNIHOHNOW CHEHA Sf d gt1 CLNV c1 EO NOIlVOHddV ADOTONHOHL HlVH HTEWIHVA HOE HTMVXH NOLLVIHOTVO EFINHAEH JEN CLNV NIDHVW SSOHD 39EZ HTEWL 001 31321 DNITCEWVS quotHOS HVEUR 3917 V CLNV C11HD EHOV39E V HOE SlSOO DNIWHVE NOISIOEHE EO HTMVXH NV 3933 HTEWL quotSE11CL1118 DNIWVHE NOISIOEHE 11 WOHE SNOISIUONOO AlHIEWlIEOHd 391Z HTEWL 39SHEEWHVE SVSNVHHV A8 SHlVH NOIldOCN Vc1 EO SLIHSEH AHAHHS 3903 HTEWL 39SHIDHlVHlS NOIlVOHddV WHNVW CLNV SdD DNIHVCIWOO SNHHJHH JEN C1ELLHOc1E1H 3961 HTEWL Lg SHIDOIONHOHL Vd SHOHVA Hog 330V Had SLSOO 81 EHEWL 617 quotquotquotquotquot 39 39STHAEH c1 HOE DNILOEHHOO HELLEV DNHCEWVS quotHOS GHQ 01 SNH lEH 39L1 HTEWL 617 39DNHCIWV S quotHOS EO SGOHLEEW WNOLLNHANOO CLNV C11HD EO SNOSIHVCEWOO lSOO NOLLVZHLLHHE 3991 HTEWL 817 bleWNV quotHOS EO 1801 CLNV HN EHOV3901 HE1c1 SE1quot1cV1V S EO HHEEWDN E1Hl NO E1218 C11HD DNITCIWV S quotHOS EO lOE1EEE1 E1Hl quotS 1 HTEWL ZV 390003399661 SEIHSHHWHG WOHE HTHLNHHO A8 GHSVHOHHE SEDIAHHS HHHJJHOIHDV NOISIOEHE EO NMOCDIVEHH 39171 HTEWL 117 0003399661 SEIHSHHWHG AHlS CLNI A8 SHEDHGOHE Ol C1E1HE1EEO SEDIAHHS OIWONOHDV WNOLUCNHL 3951 HTEWL 117 390003399661 INEWHDVNVW HHHJJHOIHDV NOISIOEHE EO WHOE EEWOS HE1CL111 HDVEHOV WlOl 39Z1 HTEWL 6S 0003 HVEUR E1Hl A8 SEDIAHHS HHHJJHOIHDV NOISIOEHE HOE CLNVWHG N1 SHSVEHONI GHlOELfOHd 3911 HTEWL SE quot 39SLNHCLNOESEH A8 C1E1C11AOHc1 SEDIAHHS OIWONOHDV WNOIHCNHL 3901 HTEWL ADOFIONHOHJJVCIWOHHSWLEMlHNGHJHOCEM 631ng LGHLNMH IMI EHEM SHIDOTONHOELL EHHHM SdOHC CLNV SHIDOTONHOELL Vc1 EO AHVTWIS AlHIEWlIEOHd 398 HTEWL 91 quotquotquotquotquotquotquotquotquotquotquot quotSdOHO Ol DNIGHOOOV ADOTONHOHL Vc1 EO SHEENHH C1ELLHOc1E1H 39L HTEWL S1 39GOHlEEW OIWONOOH CLNV HOlVWIlSH CHEHA HIHSHOHl V A8 C1E1XIV1 HO HALLVDEN HAILISOE EHEM lVHl ADOTONHOHL Vc1 WOHE SHEENHH C1EL1HOc1E1H EO AONELHOEHE 399 HTEWL 171 39GELMEHAEH EHHJN39HELLH E1Hl N1 SNOLLVNIEEWOO ADOTONHOELL Vc1 HOE SHEENHH C1ELLHOc1E1H EO AHVTWIS 39S HTEWL a GEL 31AM MLWHLHVCI do SHSAWNVOMONOOHNI GHCUITONI EHEM SlSOO NOIlVWHOENI CLNV WLIEVO NWH AONELHOEHE 3917 HTEWL 1 1 LlE AEHAEH EH lVHELLH E1Hl N1 C1E11E11NE1C11 SHOlVWIlSH CHEHA CLNV SGOHLEEW OIWONOOH 39E HTEWL 8 quotquotquotquotquotquotquotquotquotquotquotquotquotquotquot quot 396661 01 1661 WOHE SlSIWONOOH A8 GEHOHLHV39OO SHIDOTONHOELL Vc1 EO ALHIEHSVHE OIWONOOH E1Hl NO SHTOLLHV C1E1ME11AE1H EO HHEEWHN 391 EHHDIE L quotquotquotquotquotquotquotquotquotquotquot 39 39SLNEEWHOOG N1 GEL AEHAEH SHIDOTONHOELL Vc1 EO AONELHOEHE 39Z HTEWL 9 quotquotquotquotquotquotquot quotSISATVNV CLNV AHVTWIS MEHAEH EHHJN39HELLH HOE C1E1fl SHTEWIHVA 391 HTEWL 91qu 1 15 INTRODUCTION Sitespecific management is an old ideal that is intuitively appealing to many producers and agribusiness people but intuitively appealing ideas are not always profitable In the push to mechanize agriculture in the 20Lh century there was strong economic pressure to use uniform recipes over large areas to maximize returns per worker Precision agriculture PA using computers sensors and other information technology potentially allows producers to automate sitespecific management for mechanized agriculture The relatively slow adoption of PA Lowenberg DeBoer 1998 Khanna et al 1999 Daberkow and McBride 2000 has raised questions about the farm level benefits of this technology The objective of this report is to summarize and organize the publicly available studies of the profitability of precision agriculture The assumption is that any individual study or report might be in error but the general tendency of a large group of studies should be a reliable indicator This study builds on the previous reviews of the economics of precision agriculture by LowenbergDeBoer and Swinton 1997 and Swinton and LowenbergDeBoer 1998 This review includes 58 studies published since 1998 It also extends beyond the soil fertility management focus of the Swinton and LowenbergDeBoer studies to include variable rate plant populations spatial management of weeds global positioning systems for equipment guidance and yield monitoring The report includes a complete reference list and an annotated bibliography that should provide readers enough information to form their own opinions about the profitability results for a specific PA technology Sources Document sources were articles from scientific journals or proceedings 86 and nontechnical nonrefereed magazines and monographs or the intemet specializing in agribusiness services 14 Scientific refereed journals were categorized as reports that employed the scientific method to answer research questions 67 or those that described general aspects of PA 33 Documents downloaded from Internet sites were classified using the abovementioned categories For example extension publications available over the Internet written by agronomists or agricultural economists were categorized as scientific Documents available from agribusinesses were considered nontechnical or nonscientific The research questions included both the potential profitability and the adoption process of PA within the agricultural community including dealerships and producers This review has attempted to do an exhaustive review of publicly available PA economics studies available in English Omitted documents or reporting errors should be brought to the attention of the authors of this review Popular magazines comprised 75 of the nonscientific materials reviewed The remaining 25 of nonscientific materials included documents that described PA generalities Many of the PA testimonials published in the last 8 years have touched on economics This review makes no claim to an exhaustive review of this nonscientific material ANALYSIS All documents were reviewed to determine whether they reported positive returns to PA and they were classi ed by a series of variables to help identify trends and clusters The variables used to classify the studies are given in Table 1 Only descriptive statistics were used It should be noted that this review accepts the authors pro tability conclusions It does not attempt to standardize pro tability calculation methods as do Swinton and LowenbergDeBoer 1998 Table 1 Variables used for literature review summary and analysis Variable Description entry Technology VRTN PK seed ir rigation wGPS pH NPK yield monitor soil sensing none general PA summary Crop Crop Type corn soybean wheat potato sugar beet cotton barley rice oats none combinations of these Economist Economist present as author YesNo Economic Method Unsubstantiated Report Rough Partial Budget Partial Budget None Yield Estimate Method Response Yield Field Trial Simulation None Benefit YesNoMixed Time Scale Time until returns are realized YesNo Discount Rate YesNo Fertilizer Cost Seed Cost Crop PriceYield Crop Input Costs Soil Test Costs Mapping Costs Application Cost VRTPA Cost Yield Monitor Use Mentioned Human Capital Costs Information Costs Useful Life of Equipment Equipment Costs Whole Farm Benefits Environm ent Mentioned Land T enure Fertilizer cost included as input in budget YesNo Seed cost included as input in budget YesNo Crop price 39 acre or ha included in analysis Additional inputs included labor fixedvariable costs YesNo YesNo YesNo YesNo PAVariable Rate Technology cost included YesNo YesNo Consultant fees training workshops learning costs YesNo Data computer f 39 YesNo Usefulness of equipment in years YesNo YesNo YesNo YesNo Rent landlord negotiations YesNo Return to Table Listing 1 collection DESCRIPTION OF STUDIES Technology Variable rate technology VRT was the most common PA component in the literature 73 This gure is somewhat misleading since VRT is used in combination with other technologies commonly associated with FA such as GPS and GIS grid soil sampling and integrated pest management IPM Twentyone percent of the VRTrelated reports concerned nitrogen management followed by VRTPampK 5 and VRTpH 3 Nonspecific VRT reports 23 reviewed the technology in general or as a combination of the above technologies Variable rate seeding 7 and irrigation 2 followed VRT fertilizer management strategies in report frequency Seven percent of the reports dealt with weed management and pest control using VRT Yield monitors and GPS were reviewed in conjunction with VRT in 5 and 2 of the reports respectively Five articles dealt specifically with soil sensing 4 Twentysix percent of the reviews summarized the economic benefits of PA technology Crops 7 Fiftyfour of the articles reviewed discussed economic returns generated by experiments with or application of PA technology with corn Wheat 13 sugar beet 3 potato 4 and soybean 3 followed corn There were nine reports discussing variable rate technologies applied to comsoybean rotation systems 9 Table 2 Frequency of PA Technologies Reviewed in Documents Technology Percent VRT Nitrogen 21 VRT Phosphorous and potassium 5 VRT Weeds or pests 5 VRT Seeding 7 VRT pH 3 VRT Yield Monitor 5 VRTGPS Systems 2 VRT Irrigation 2 VRT Combinationgeneral 23 Soil Sensing 4 PA technology summaries 26 Total Number of Documents 133 Variable rate technology Numbers do not sum to 100 because of rounding error Return to Table Listing Barley was reviewed in 2 of the articles while oats cottoncom and ricecom rotation systems cotton and sorghum were each 1 of the subject crops in the literature reviewed Thirtyseven entries were recorded as quotnot applicablequot since the subject matter concerned adoption patterns the current state of PA or PA in general 28 A quotvariablequot category 4 of the literature indicated that the authors were not specific as to which crop was under investigation for example the term quotgrainquot may have been used throughout the report Economists 7 Like other branches of science economics has timetested methods usually learned through university level education Noneconomists often add fresh insights based on nonstandard methods of analysis Do economists and noneconomists arrive at the same conclusions It was not possible to determine the training of all authors Current employment was taken as a proxy for economic training It was assumed that those employed by economics organizations eg university economics or agricultural economics departments USDA Economic Research Service had substantial training in economic methods Authors employed by economic or agricultural economic institutions authored 66 of all the material reviewed Of the 108 documents reporting pro tability analyses individuals employed by economics organizations authored 57 Twelve percent of the articles reviewed were written by individuals employed by the agribusiness sector Ten articles of the articles with agribusiness authorship provided pro tability analyses The number of studies of precision agriculture with input from economists has grown Fig 1 In the early 1990s the only economic evaluation of precision agriculture was in the form of rough pro tability estimates that appeared in agronomic studies 25 20 I No Econom39sts Each 5 5 15 D E Z 10 5 h ii 0 Illm E5 E5 as u u u 0 Jgt l L66L zeeL 866L 4 666L 8 966L 966L Y r Figure 1 Number of reviewed articles on the economic feasibility of PA technologies co authored by economists from 1991 to 1999 Return to Figures Listing The rst studies coauthored by economists appeared in 1993 In 1998 and 1999 over 20 articles or reports on PA appeared annually with authorship by economists Economic methods Three general categories grouped methods used to evaluate the economic feasibility of a practice unsubstantiated reports rough partial budgets and partial budgets Articles or reports providing lump sum numerical estimates suggesting the pro tability or negative returns attributable to a practice without supplying detailed information about changes in costs and revenue were classi ed as unsubstantiated reports The changes in costs sought include input costs seed fertilizer dryer fuel costs of the technology employed applicator costs information costs and data management computer costs hardware software training costs learning costs lag timetime lost sinking funds or discount rates net present value equipment costs and equipment life span rental rates sinking fund depreciation custom service chargesconsulting charges soil test costs mapping costs labor costs involved with any of these activities Reports that mentioned the existence of these details but failed to enumerate them during analysis or glossed over input details were labeled as quotrough partial budget analysisquot Rough partial budget analysis generally provided a table demonstrating the change in costs caused by the addition or practice of a technology component compared to standard operating expenses For example variable rate nitrogen application may have been compared with conventional fertilizer treatments Returns from both practices may have been compared in tabular form but additional costs incurred by soil testing lab analysis and variable rate applicator cost were often not factored or were taken for granted and buried in the text Partial budget analysis documented most or all of the above mentioned costs Examples of detailed partial budgets are found in LowenbergDeBoer and Swinton 1997 LowenbergDeBoer 1999 and Swinton and LowenbergDeBoer 1998 Some reports implemented dynamic optimization models that incorporated detailed partial budgets ie Isik et al 1999 Feinerman Eli and Eshel Bresler 1989 Letey J H Vaux and E Feinerman 1984 and Schnitkey et al 1996 Optimization model articles were subsumed under the quotpartial budgetquot category When no numerical economic analysis was provided but positive returns were attributed to a particular technology the category quotnot applicablequot was used Yield Estimators 7 Swinton and LowenbergDeBoer 1998 hypothesize that the method of yield estimation in uences PA economic results In particular they find that studies using simulation are more likely to show positive benefits than those based on field trials This is because simulation models do not include all of the possible production constraints they usually assume that factors not included in the model are at nonlimiting levels Three categories were used to define the yield estimators found in the literature response functions field trials and simulation models In a sense all three of these are methods meant to mimic crop response under alternative agronomic practices The response functions and crop growth models are digital simulations while eld trials are analog simulations Response functions are generally single equations often quadratic that estimate the yield of a given crop in relation to a given set of inputs such as fertilizer plant population or lime Since the inputs are generally economically quantifiable response functions facilitate comparison between input changes and the cost of making those changes Response functions are also useful for modeling exercises About 23 of documents reporting benefits used response functions Crop growth models are usually complex multiequation simulations that attempt to mimic the physiological processes of plants in computer code for example see reference Watkins et al 1998 They are typically built and validated with field trial data They incorporate growth coefficients and other information from a wide range of scientific studies About 22 of documents reporting benefit estimates used crop growth simulation Field trials are meant to mimic crop response to agronomic practices in farmer s fields but typically on a smaller area and with more control They have the advantage of re ecting a broader range of yield limiting factors than the response functions or crop growth simulation Sometimes questions are raised about how representative of trial sites are the limited number of weather years and the great care lavished on trial plots The classic small plot trials use plants grown on plots of a few square yards on an experiment station to extrapolate results to crops grown by farmers over thousands of acres Yield monitors and other PA technology have allowed these experiments to approach farm scale Ordinarily agronomic practices follow an experimental design that facilitates comparison between treatments Usually that design involves some type of linear additive model created to compare average results between treatments with a statistical technique called Analysis of Variance Sometimes those doing field trials claim that they do not use a model In fact their results depend on a very specific and highly restrictive model of crop response About 40 of documents reporting benefits used field trial data When no yield estimator was presented 13 quotnot applicablequot NA was entered as a data point About 13 of the studies falling into the NA category for both the economic methods and yield estimator questions Table 3 Economic methods and yield estimators identi ed in the literature review ed Analysis Methods Percent Economic Method Partial Budget 50 Rough Partial Budget 19 Unsubstantiated Reports 20 Not Applicable 11 Total Number of Documents 108 Yield Estimator Simulation 22 Response Function 23 Field Trial 40 Not Applicable 13 Total Number of Documents 108 Return to Table Listing Time Scale and Discount Rate Factors relating to time scale include the period of test validity soil tests yield maps whether costs were spread out over an acrestime period and the net revenue period for example Isik et a1 1999 and Lowenberg DeBoer et a1 When these details were mentioned in reports they were noted Twentyseven percent of the articles reviewed included one or more of these factors in a budget analysis The general heading quotdiscount ratequot refers to any report that included annuity amortization sinking funds or net present value of any production inputs including PA technologies in budget analyses Discount rate was included in budget analyses in 35 of the articles Input and VRTPA Costs Input costs considered in this review were fertilizer costs seed costs application costs and any variable and fixed costs mentioned by the authors Variable rate technology and PA costs were considered separately for comparative purposes to verify whether benefits espoused by the authors included PA technology costs other farm input costs and crop yield Ninety percent of the reports included farm inputs in budget analyses including budget details while 81 included PA technology costs Human Capital and Information Costs Conventional economic feasibility studies of PA technology have often failed to include human capital and information costs in budget analyses see Anonymous 1996 LowenbergDeBoer 1995 LowenbergDeBoer and Boehlie 1996 LowenbergDeBoer 1997 and Swinton and LowenbergDeBoer 1998 for examples One article reported a service fee of 2557acre including grid sampling soil test and variable application charges Thrikawala et al 1999 Another study reported consultant fees of 050acre Swinton SM and J LowenbergDeBoer 1998 which quickly adds up when breakeven prices balance on pennies Table 4 lists the human and information costs either used in budget analyses or mentioned in reports In all 31 of the articles reporting economic bene ts included human capital costs Under the category quotInformation costsquot an item labeled information costs refers to costs associated with grid soil sampling lab testing GPS services or any PA activity that generates useful information used to change a management strategy When information costs were grouped together 44 of the reports included or mentioned the role information costs in determining the economic feasibility of PA Additional Variables Other variables considered in the literature review included yield monitor use PA equipment cost and life span or environmental issues related to PA Little to no empirical data eXists regarding the environmental impacts of precision agriculture but 25 of these documents report potential environmental benefits Likewise many reports did not explicitly include equipment cost and yield monitor use and lifespan in their feasibility assessments Only 29 of all studies reviewed included equipment costs in calculations or even mentioned them Some 35 of all studies mentioned yield monitor use and 17 of all studies specified the useful life of equipment in their estimates Table 4 Frequency Human Capital and Information Costs were included in economic analyses of PA literature reviewed Input Type Percent Human Capital Labor 24 Labor and learning costs 2 Labor and training costs 1 Labor workshop and training costs 2 Human capital costs mentioned not defined 2 Not mentioned 69 Base 1 08 Information Costs Data management 6 Data management and computer 1 Computer and information costs 6 Information costs 7 Data management information costs 2 Data management computer and information costs 3 Information costs mentioned 19 Not mentioned 56 Base 1 08 Information castsquot refers to costs associated with grid soil sampling lab testing GPS services or any PA activity that generates useful information used to change a management strategy Return to Table Listing REPORTED BENEFITS Whether authors reported the technology had positive negative or mixed returns was recorded Though this category seems to be objective it often is not An objective comparison would require consistent methodology over all studies similar to the analysis of nine VRT fertilizer studies by Swinton and Lowenberg DeBoer 1998 All of the studies reviewed in this section dealt with economic returns but as noted above calculation of returns differed A subjective element may enter into the choice of which costs and returns to include There is also a subjective element in deciding on the criteria for a positive benefit Does a positive benefit mean that the overall average return is positive Does it mean that return is positive in a certain percentage of site years ie 50 There is also a question about the time period over which benefits are realized Mixed results indicated that although there may have been some positive net returns the authors did not have enough confidence to support the general assertion that similar results could be achieved under similar circumstances Oftentimes conclusions in these reports indicated that more research needed to be done in order to reach a valid conclusion Negative results have a subjective component as well Like positive results reports that concluded a technology or combination thereof as applied to a certain crop were not worthwhile was apparent in the numbers and equally apparent in the tone of the narrative Some treatment results may have generated positive returns but not enough for the authors to conclude that the investment was economically feasible However other reports provided sufficient evidence that a given technology produced de facto negative returns for a given crop Overall Results Of the 108 studies that reported economic results 69 indicated positive net returns for a given PA technology while 12 indicated negative returns There were 21 articles indicating mixed results 19 Of the 62 documents reporting benefits authored by economists 73 reported positive benefits from PA 11 reported mixed results and 16 negative results Table 6 Of the nine documents with agribusiness authors reporting benefits twothirds 66 of these articles reported positive results from PA while two articles 22 reported mixed results Only one article 11 written by an individual employed by the agribusiness sector reported negative returns In terms of positive benefits economists and agribusiness authors seem to be coming to be coming to the same conclusions The percentage of documents showing positive results was only slightly lower for studies using field trial data than for those which used response functions or simulation to estimate yield Table 6 Positive results were reported for 60 of response functions studies 67 of field trial studies and 75 of crop growth simulation studies Unsubstantiated studies showed about the same percentage of positive results as those using partial budgets Table 6 About 68 of the unsubstantiated studies showed positive results and 64 for the partial budgets When all the studies are categorized by crop corn soybean and sugar beet studies showed positive pro ts in over two thirds of cases Table 7 Fortytwo percent of the studies on wheat showed pro ts Of those studies reporting numerical estimates for VRT N 72 of corn studies and 20 of wheat studies showed pro ts Table 8 Table 5 Summary of reported bene ts for PA technology combinations in the literature reviewed Technology Reported Bene t m M MiXed VRT N 63 15 22 27 VRTP K 71 29 0 7 VRTWeeds Pests 86 14 0 7 VRTpH 75 0 25 4 VRTGPS Systems 100 0 0 3 VRTIrrigation 50 0 50 2 VRTSeeding 83 17 0 6 VRT Yield Monitor Systems 43 14 43 7 VRT N39PK General 75 8 16 24 Soil Sensing 20 40 40 5 PA Technology Summary 77 0 23 14 PAVRT Technologies combined 63 ll 27 108 These gures considered reports estimating the bene ts of yield monitors in conjunction with VRT not yield monitors alone Return to Table Listing The level of returns varies widely by crop and technology Table 9 The average return to VRT N in sugar beet studies is 74acre 4825 net Estimated returns to VRT lime on 25 acre grids in Indiana varied from 346a to 507a Reported returns to site speci c fertility management in corn and soybean systems range from losses of over 100a to gains of 80a The reported range of VRT plant populations for corn is 097a to 272a VRT weed control returns varied depending on weed pressure and patchiness from 001a to 1167a GPS guidance bene ts were estimated at about 052a compared to foam markers for the producer who already has a GPS Unlike VRT fertilizer or pesticide yield monitor bene ts have been dif cult to estimate because they often extend to the whole farm For example if a producer uses a yield monitor to identify a good hybrid that hybrid will be planted on many elds not just the eld on which the hybrid comparison was made All the yield monitor studies reviewed were rough partial budgets No study has evaluated yield monitor bene ts at the whole farm level In Table 5 for example pro tability studies considered yield monitors coupled with some form of VRT As discussed results from feasibility studies are highly 14 variable and contextspecific It would be expected that studies looking at the combination of VRT and yield monitors would demonstrate mixed results Recent reports Farm Industrv News 2000 have A J returns on investment for yield monitors and guidance systems after a single growing season Some PA technologies and crops are notable by their absence Apparently there are no publicly available studies of the economics of remote sensing for agriculture None of the economic studies focused on horticultural or orchard crops Table 6 Frequency of reported bene ts from PA technology that were positive negative or mixed by authorship yield estimator and economic method Re orted Benefits l xed m Economist Articles authored by Economists Count Yes 61 62 73 11 16 No 39 46 63 13 24 Base 108 Yield Estimator Articles Using Method Response Function 23 25 60 28 12 Field Trial 39 43 67 19 14 Simulation 25 26 75 8 17 Not Applicable 13 14 79 0 21 Base 108 Economic Method Articles Using Method Unsubstantiated 20 22 68 27 5 Partial Budget 69 74 64 16 16 None 11 12 75 25 0 Base 108 Rough partial budgets were combined with partial budgets 10 of the authors in this category were affiliated with or employed by the agribusiness sector Though not formally identified as economists it is assumed individuals representing agribusiness companies have minimally practical financial and economic experience if not more advanced academic degrees in a related 1e Return to Table Listing Table 7 Reported bene ts of PA technology according to crops Cro Bene t from PA Technolo E M Mixed Cases Corn 69 15 17 48 Potato Y 3 N 1 0 4 Wheat 42 33 25 12 Soybean Y 2 Sugar beet 80 20 5 Barley Y 2 Oats Y 1 Corncotton Y 1 Cornsoybean 89 11 9 Comrice Y 1 Cotton Y 1 Sorghum Y 1 YesNo reported bene t Return to Table Listing Table 8 Pro tability summary of PA technologies and crops where technologies were implemented m Corn Potato Wheat S oybe an Sugar beet Cornsoybean T e chnology VRT N VRT seeding Corn VRT WeedPests Corn Wheat S oybe an VRT lrrigation Corn Cornc otton VRT PK Corn Potato Corn soybean Wheat Corn Sorghum Cotton Corn Corn soybean VRTYield Monitor VRTpH Corn Sugar beet Soil Sensing Cornsoybean VRTGeneral Barley Cornsoybean Cornrice Reported Bene t from PA Technologv m 72 20 Y39 Y Go L gtltgtlt lt8 lt lt lt lt gt lt tlt7 lt7 lt1 lt1 lt1 lt1 tlt1 m 6 N 4o 22 N xed 22 40 M M 333339 Z 25 20 m u NNN Ho HH Hmmmm m b w HM m Studie s 1 8 Y reported benefit N no reported benefit M mixed results Return to Table Listing Table 9 Reported net returns from PA technology Technology Crop comments Returns from VRT Reportedquot Net Conventional Return Practice 1 acre VRTNPK Corn See reference 549 115 664 Corn See reference 960011100 Corn 3 yrs See reference 27945 29884 1939 Soybeancorn 3 yrs See reference 30543 32102 1559 VRTN Beets See reference 102500 109900 7400 gross 4825 net Soybeancorn Site 1 See reference 16827 16732 095 Soybeancorn Site2 See reference 15963 17089 1153 Wheat See reference 6853 7618 765 Wheat See reference 437 910 473 Wheat barley See reference 3126 Corn See reference 26900 23325 3575 Corn See reference 1970031500 2040032600 7001100 Corn See reference 10800 12600 1800 application rate based on soil tests Corn See reference 10800 11700 900 application rate based on yield map VRTN P Wheat See reference 13194 10657 2537 avg yield goal used for fertilizer rec 80 kgha 10745 10844 099 Wheat See reference 11969 6485 5484 Sitespeci c yield goal used for fertilizer rec Note values are the mean of lowest and highest results reported Assume that VRT includes soil sampling costs grid or otherwise consulting fees application costs equipment purchase or rental costs and any other additional costs controller vs manual applicators Table 9 Reported net returns from PA technology continued Technology Crop comments Returns from VRT Reportedquot Net Reference number Conventional Return 1 acre Practice VRT P K Corn See reference 18826 18725 101 Corn See reference 241 Corn Wgrid sampling See reference 9144089 Wheat See reference 10548 11579 1031 Soybean See reference 15672 15959 287 Potato See reference 1015 Corn See reference 13963 142 86 323 VRTpH lime Corn See reference 16365 17053 6 88 AgroEconomic decisions combined Corn See reference 15474 15901 426 25acre grid AgroEconomic decisions combined Corn See reference 15474 15656 182 lacre grid AgroEconomic decisions combined Corn See reference 3904 3614 290 application grid vs conventional soil sampling compared costs notnet returns VRTSeedng Corn See reference 177 Agronomic Decision Corn See reference 193 Economic Decision Corn See reference 100 gross using GIS and soil electrical conductivity Note values are the mean of lowest and highest results reported Assume that VRT includes soil sampling costs grid or otherwise consulting fees application costs equipment purchase or rental costs and any other additional costs controller vs manual applicators Agronomic decision fertilizer recommendations are based on conventional rates usually found in extension publications Economic decision an increased fertilization rate applied to a specific area is justified Where returns produced by an increase in crop yield equals or is more than the application costs of that additional amount applied Table 9 Reported net returns from PA technolog39es continued Technology CornPK grid soil tests CornPK soil type CornLime grid soil test CornNPK and seeding ComVRT soil testing Simulation using actual production data CornVRTN Based on Avg Com Price ofSIOSMg and two growing seasons ComVRT General Simulation Complete Partial Budget included GPS GPS Corn PA General Complete partial budget included GPS Benefits compared to foam marker systems Comments Information only Uniform rate Using VRT N Cost 0551b 0641b 0731b Field SizeCVField Fertility 50ha2555 N kgha 50ha2580 N kgha 50ha5055 N kgha 50ha5080 N kgha 200ha2555 N kgha 200ha2580 N kgha 200ha5055 N kgha 200ha5080 N kgha 500ha2555 N kgha 500ha2580 N kgha 500ha5055 N kgha 500ha5080 N kgha Reportedquot Net Return 1 acre Net Return 391 acre Mean See reference 1026 077 097 1415 Net Return 391 acre See reference 574 328 Net Returns 391 ha N12 See reference 3249 3640 3849 Net Return 391 ha See reference 10805 10752 10553 7292 1823 1761 1571 1690 027 035 164 8000 Net Return 391 ha See reference 4701 Net Return 391 acre See reference Producers owning equipment GPS Guidance 029 Lightbar only 052 Custom applicators hired GPS Guidance only 030 GPS Guidance 010 20 Table 9 Reported net returns from PA technologies continued Technology Comments Reportedquot Net Return 1 acre Grid Soil Sampling Grid Soil Sampling Base on VRT costs and returns Fertilizer applied unknown Yield mappingJr With VRTPK VRTpH field drainage repairs Weed Control Corn Corn Simulation S oybean Simulation Grid point 106ft Grid point 212ft Grid point 318ft Cell area 318ft Grid point 100ft Grid point 200ft Grid point 300ft Weed pressurepatchiness L owL ow Weed pressurepatchiness L owL ow MeanNet Return 391 acre See reference 040 025 262 679 MeanNet Return 391 acre See reference 244 895 1016 Application costs reduced from 10374 to 8424 low yield land and 9624 highyield land See reference 71321 gross margin See reference Net Return 391 ha See reference 1250 Net Return 391 acre See reference 001764 Net Return 391 acre See reference 1941164 Tlncludes combinations soil testing and various variable rate technologies Return to Table Listing 21 CONCLUSIONS This review the economic studies of precision agriculture indicates that about two thirds of all studies report bene ts and another quarter report miX results Consistent with previous reviews of the literature high and consistent bene ts are reported for site speci c N management in sugar beets Modest positive returns are reported for variable rate lime sitespeci c weed management GPS guidance and variable rate plant populations when yield potentials vary widely in the eld Estimated pro tability of VRT fertilizer ranges from substantial losses relative to whole eld management to substantial ga1ns Pro tability results do not appear to differ substantially by type of economic analysis authorship of the report or source of yield estimates The percentage of studies using crop growth simulation or response functions which report positive bene ts is about 10 higher than for studies using eld trial data Reported bene ts from VRT are varied Findings might be confused by crop type application techniques applied elements N P andor K the quality of eld reconnaissance maps and concomitant fertilizer recommendations management strategies and eld history or uncontrollable variables such as weather or other climactic factors Furthermore unlike yield monitors paybacks from variable rate systems are more of a function of time 22 REFERENCE SECTION Ahmad Saeed Raymond J Supalla and William Miller 1997 Precision farming for profits and environmental quality problems and opportunities Paper prepared for the Annual Meeting of Agricultural Economics Association Toronto Canada July 2730 1997 Ahlrichs John S 1993 Computerized record keeping for variable rate technology Soil specific crop management proceedings of the lst workshop p 325333 ASNCSSNSSSA Akridge Jay and Linda Whipker 1998 Sharper look at the leading edge Farm Chemicals 1616 1215 Purdue precision agriculture services survey 1 Akridge Jay and Linda Whipker 1996 1996 precision agricultural services dealership survey results Staff paper 9611 Center for Agricultural Business Purdue University West Lafayette IN 2 Akridge Jay and Linda Whipker 1997 1997 precision agricultural services dealership survey results Staff paper 9710 Center for Agricultural Business Purdue University West Lafayette IN 3 Akridge Jay and Linda Whipker 1998 1998 precision agricultural services dealership survey results Staff paper 9811 Center for Agricultural Business Purdue University West Lafayette IN 4 Akridge Jay and Linda Whipker 1999 1999 precision agricultural services dealership survey results Staff paper 996 Center for Agricultural Business Purdue University West Lafayette IN 5 Akridge Jay and Linda Whipker 2000 2000 precision agricultural services dealership survey results Staff paper 0004 Center for Agricultural Business Purdue University West Lafayette IN Anonymous 1996 Grids value for beets The Sugar beet Grower February 1996 p 1415 Atherton BC MT Morgan SA Shearer TS 39 39 and AD Ward 1999 Sitespecific farming a perspective on information needs benefits and limitations Journal of Water and Soil Conservation 2quotd Quarter 1999 Atwood Joseph A and Glenn A Helmers 1998 Examining quantity and quality effects of restricting nitrogen applications to feedgrains American Journal of Agricultural Economics 80 369381 23 Audsley E 1993 Operational research analysis of patch spraying Crop Protection 12 1 111 19 Babcock Bruce A and Gregorv R Paustch 1998 Moving from uniform to variable fertilizer rates on Iowa corn effects on rates and returns Journal of Agricultural and Resource Economics 232 385400 Barnhisel RI MJ Bitzer JH Grove and SA Shearer 1996 Agronomic benefits of varying corn seed opulations a central Kentucky Study Precision agriculture proceedings of the 3r international conference June 2326 Minneapolis MN p957966 ASNCSSNSSSA Bauer Troy A and David A Mortensen 1992 A comparison of economic and economic optimum thresholds for two annual weeds in soybeans Weed Technology 61 228235 Beuerlein Jim and Walter Schmidt 1993 Grid soil sampling and fertilization Agronomy and Technical Report 9302 Ohio State University r Bongiovanni Rodolfo and James LowenbergDeBoer 1998 of variable rate lime in Indiana Precision agriculture proceedings of the 43911 international conference July 1922 p 16531665 ASNCSSNSSSA Bongiovanni Rodolfo and James LowenbergDeBoer 2000 Management in corn using sitespecific crop response estimates from a spatial regression model Paper presented at the 5 International Precision Agriculture conference Minneapolis MN July 2000 Braga RP JW Jones and B Basso 1999 Weather induced variability in sitespecific management profitability a case study Precision agriculture proceedings of the 4Lh international conference July 1922 p 18531863 ASNCSSNSSSA Bruulsema TW GL Malzer RC Davis and PJ Copeland 1996 Spatial relationships of soil nitrogen with corn yield response to applied nitrogen Precision agriculture proceedings of the 3rd international conference June 2326 Minneapolis MN p505512 ASNCSSNSSSA Buchholz Daryl D Unknown date Missouri grid sampling project Unpublished document University of Missouri Soil Fertility Agronomy Extension 214 Waters Hall Columbia MO 65211 Bullock Donald G David S Bullock Emerson D Nafziger Thomas A Doerge Steven R Paszkiewicz Paul R Carter and Todd A Peterson 1998 Does variable rate seeding of corn pay Agronomy Journal 90830836 24 Bullock David S and Donald G Bullock 1999 From agronomic research to farm management guidelines a primer on the economics of information and precision technology Draft in progress Nov 1 1999 Carr PM GR Carlson JS Jacobson GA Nielson and E0 Skogley 1991 Farming soils not elds a strategy for increasing fertilizer profitability Journal of Production Agriculture 41 5767 Casaday William W and Raymond E Massey 1999 The growth and development of precision agriculture service providers Precision agriculture proceedings of the 4 international conference July 1922 p 17571765 ASNCSSNSSSA Cattanach A D Franzen and L Smith 1996 Grid soil testing and variable rate fertilizer application effects on sugar beet yield and quality Precision agriculture proceedings of the 3rd international conference June 2326 Minneapolis MN p1033 1038 ASNCSSASSSA Clav SA GJ Lems DE Clav MM Ellsburv and F Forcella 1999 Targeting precision agrichemical applications to increase productivity Precision agriculture proceedings of the 4th international conference July 1922 p 16991707 ASNCSSNSSSA Colbum J W 1999 Soil doctor multiparameter realtime soil sensor and concurrent input control system Precision agriculture proceedings of the 4Lh international conference July 1922 p 1693 ASNCSSNSSSA Daberkow Stan G and William D McBride 1998 Adoption of precision agriculture technologies by US corn producers Precision agriculture proceedings of the fourth international conference part B p 18211831 ASACSSASSSA Madison WI Daberkow Stan G and William D McBride 1998 Socioeconomic profiles of early adopters of precision agriculture technologies Journal of Agribusiness 162 151168 Daberkow Stan G J FernandezComeio and WD McBride 2000 The role of farm size in the adoption of crop biotechnology and precision agriculture Selected paper for presentation at the 2000 AAEA meetings Tampa FL July 30August 2 Doerge Tom 1999 Yield monitors create on and offfarm profit opportunities Crop Insights Pioneer Intemational 914 p 14 English Burton C SB 39 39 39 39 and Roland K Roberts 1999 F 39 and environmental benefits of variable rate application of nitrogen to corn fields role of variability and weather Selected paper for the annual meeting of the American Agricultural Economics Association Nashville TN Aug 811 1999 25 English BC RK Roberts and SB 39 39 39 39 39 1999 Spatial breakeven variability for variable rate technology adoption Precision agriculture proceedings of the 43911 international conference July 1922 p 16331642 ASNCSSNSSSA English Burton Roland Roberts and David Sleigh 2000 Spatial distribution of precision farming technologies in Tennessee Research Report 0005 Department of Agricultural Economics and Rural Sociology University of Tennessee Knoxville February 2000 Fairchild D and M Duffy 1993 Working group report In Sitespecific management for agricultural systems p 245253 ASNCSSNSSSN Madison WI Farm Indust News 2000 How to access precision agriculture technologies Internet document wysiwyg3httpserviceindustryclickcomspecialsectionstorycfmvocagcampid83 Feinerman Eli and Eshel Bresler 1989 Optimization of inputs in a spatially variable natural resource unconditional vs conditional analysis Journal of Environmental Economics and Management 17 140154 Fiez Timothv E Baird C Miller and William L Pan 1994 A of spatially variable nitrogen fertilizer management in winter wheat Journal of Production Agriculture 71 8693 Finck Charlene 1998 Precision can pay its way Farm Journal MidJanuary 1998 p 1013 Finck Charlene 1997 The learning curve Farm Journal MidFebruary 1997 p 67 Fixen PE and HF Reetz Jr 1995 Sitespecific soil test interpretation incorporating soil and farmer characteristics Sitespecific management for agricultural systems proceedings from the 2quotd international conference March 2730 Minneapolis MN p 731743 ASNCSSNSSSA Forcella Frank 1993 Value of managing withinfield variability Soil specific crop management proceedings of the 1St workshop Madison WI p 125132 ASNCSSNSSSA Fountas Spyridon 1998 Market research on the views and perceptions of farmers about the role of crop management within precision farming Master of Science Thesis Silsoe College Cranfield University Available at httpwwwsilsoecranfiehttpwwwsolsoecranfieldaculdcpfpapersspyridon Fountas indeXhtmldaculdcpfpapersspyridon FountasindeXhtm 26 Godwin RJ IT James JP Welsh and R Earl 1999 Managing spatially variable nitrogen 7 a practical approach Presented at the Annual ASEA meeting Paper N0 99 1142 2950 Niles Road St Joseph MI 490589659 USA Griffin Terry Caleb Oriade and Carl Dillon 1999 The economic status of precision farming in Arkansas Department of Agricultural Economics University of Arkansas Fayetteville 1999 Griffin TW JS Popp and DV Buland 2000 Economics of variable rate applications of phosphorous on a rice 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of Agricultural Economics 72 9971005 Haves JC A Overton and JW Price 1994 Feasibility of sitespecific nutrient and pesticide applications Environmentally sound agriculture Proceedings of the 2H conference April 2022 1994 Orlando FL St Joseph MI Heiniger RW and AM Meiier 2000 Why variable rate application of lime has increased grower pro ts and acceptance of precision agriculture in the southeast Heisel T and S Christensen 1999 A digital camera system for weed detection Precision agriculture proceedings of the 4th international conference July 1922 p 15691577 ASNCSSNSSSA Henessv David A Bruce A Babcock and Timothy E Fiez 1996 Effects of site specific management on the application of agricultural inputs Working paper 96WP 156 March 1996 Center for Agricultural and Rural Development Iowa State University Ames IA 500111070 27 Hennessey David and Bruce Babcock 1998 Information exibility and value added Information Economics and Policy 10431449 Hertz Chad A 1994 An 39 evaluation of variable rate phosphorous and potassium fertilizer application in continuous corn MS Thesis Department of Agricultural Economics University of Illinois UrbanaChampaign Hertz Chad A and John D Hibbard 1993 A preliminary assessment of the economics of variable rate technology for applying r39 an r 39 in corn r 39 Farm Economics 9314 Department of Agricultural Economics University of Illinois Champaign Urbana 1 Hollands KR 1996 Relationship between nitrogen and topography Precision agriculture proceedings of the 3rd international conference June 2326 Minneapolis MN p312 ASACSSNSSSA Hombaker Robert H Roderick M Rejesus and Gary D Schnitkey 2000 Development and validation of a variable rate nitrogen program in Central Illinois Proceedings of the 5 International Conference on Precision Agriculture and Other Resource Management July 1619 2000 Radisson Hotel South Bloomington Minnesota USA Hoskinson Reed L and J Richard Hess 1999 Using the decision support system for agriculture DSS4AG for wheat fertilization Precision agriculture proceedings of the 4th international conference July 1922 p 17971806 ASNCSSNSSSA Isik Murat Madhu Khanna and Alex WinterNelson 1999 I in sitespecific crop management under uncertainty Paper presented at the Annual Meeting of American Agricultural Economics Association August 811 1999 Nashville Tennessee Issaka Mahaman 1993 An evaluation of soil chemical properties variation in northern and southern Indiana PhD Thesis Department of Agronomy Purdue University West Lafayette IN Kasowski Mike and Dave GenereuX 1994 Farming by the foot in the Red River valley Agri Finance December p 20 Kessler Mark C and J LowenbergDeBoer 1998 39 analysis of yield monitor data and its use in finetuning crop decisions Precision agriculture proceedings of the 43911 international conference July 1922 p 821828 ASNCSSNSSSA Khanna Madhu 1999 Sequential adoption of sitespecific technologies and its implications for nitrogen productivity a double selectivity model Selected paper for the annual meeting of the American Agricultural Economics Association Nashville TN Aug 8111999 28 Khanna Madhu Onesime Faustin Epouche and Robert Hombaker 1999 Sitespecific crop management adoption patterns and incentives Review of Agricultural Economics 212 455 472 Kitchen NR DF Hughes KA Sudduth and SJ Birrell 1994 Comparison of variable rate to single rate nitrogen fertilizer application corn production and residual soil N03N Sitespecific management for agricultural systems proceedings from the 2quotd international conference March 2730 Minneapolis MN p 427439 ASNCSSNSSSA Letey J HJ VauX and E Feinerman 1984 Optimum crop water application as affected by uniformity of water infiltration Agronomy Journal 76 MayJune 435441 Long DS GR Carlson and GA Nielsen 1996 Cost analysis of variable rate application of nitrogen and phosphorus for wheat production in northern Montana Precision agriculture proceedings of the 3rd international conference June 2326 Minneapolis MN p10191032 ASNCSSNSSSA Lilleboe D 1996 Will it pay The Sugar beet Grower February p 1820 Linslev CM and FC Bauer 1929 Test your soil for acidity Circular 346 University of Illinois Agriculture Experiment Station Le Quintrec Robert M A D Boisgontier and G Grenier 1996 Determination of field and cereal crop characteristics for spatially selective application of nitrogen fertilizers Precision agriculture proceedings of the third international conference June 2326 Minneapolis MN p 303313 ASACSSASSSA LowenbergDeBoer J R Nielsen and S Hawkins 1994 Management of intrafield variability in largescale agriculture a farming systems perspective SystemsOriented Research in Agriculture and Rural development International Symposium Montpellier Francs November 2125 1994 p 551555 LowenbergDeboer Jess 1995 Economics of precision farming payoff in the future Paper presented at the Precisions Decisions Conference Champaign Illinois November 2728 1995 LowenbergDeBoer J 1995 Management of precision agricultural data Selected paper presented at the Annual Meeting of the American Agricultural Economics Association Indianapolis August 1995 LowenbergDeboer Jess Steve Hawkins and Robert Nielson 1994 E 39 of precision farming Extension Manual Department of Agricultural Economics Purdue University West Lafayette IN 47907 29 LowenbergDeBoer Jess 1996 Precision farming and the new information technology implications for farm management policy and research discussion American Journal of Agricultural Economics 78 12811284 LowenbergDeBoer J and M Boehlie 1996 Revolution evolution or deadend economic perspectives on precision agriculture Proceedings of the 3rd international conference June 2326 Minneapolis MN p 923944 ASNCSSNSSSA LowenbergDeBoer J 1997 Taking a broader view of precision farming bene ts Modern Agriculture 12 3233 AprilMay 1997 LowenbergDeBoer J 1997 Bumpy road to adoption of precision agriculture Purdue Agricultural Economics Report November 1997 p 14 LowenbergDeboer Jess 1997 Economics of precision farming implications for the Canadian prairies In Farming to the Future Precision Agriculture Conference Brandon Manitoba November 1997 LowenbergDeBoer J and SM Swinton 1997 F 39 of sitespecific management in agricultural crops In Sitespecific management for agricultural systems p 369396 ASNCSSNSSSN Madison WI LowenbergDeBoer J 1998 F 39 of variable rate planting by yield potential zones Purdue Agricultural Economics Report May 1998 p 67 LowenbergDeBoer J 1998 Precision agriculture in Argentina Earth Observation Magazine Spring p MA13MA15 LowenbergDeBoer J 1998 Adoption patterns for precision agriculture Agricultural Machine Systems SP1383 Society for Automotive Engineers Warrendale PA September 1998 LowenbergDeBoer J 1998 F 39 of variable rate planting for corn Precision agriculture proceedings of the 4Lh international conference July 1922 St Paul MN p 16431651 ASNCSSNSSSA LowenbergDeBoer J 1998 What price is right Farm Chemicals 1614 2023 LowenbergDeBoer Jess 1999 GPS based guidance systems for farmers Purdue Agricultural Economics Report December 1999 p 89 LowenbergDeBoer J 1999 Adoption of GPS based ghuidance systems in agriculture Successes in precision agriculture proceedings of the 4 annual conference Brandon Manitoba November 1999 httpdmamoecnpuhttpwwwsolsoecranfieldaculdcpfpapersspyridon Fountasinde XhtmrdueeduNbiehlSiteFarminpublicationshtml 30 LowenbergDeBoer J and Anthonv Aghib 1999 Average returns and risk characteristics of sitespecific P and K management eastern corn belt onfarm trial results Journal of Production Agriculture 122 276282 LowenbergDeBoer J 2000 F 39 analysis of precision farming In Agricultura de Precisao Borem Aluizio Marcos Giudice Daniel Marcal Evandro Mantovani Lino Ferreira and Reinaldo Vale e Gomide eds Federal University of Vicosa Vicosa MG Brazil LowenbergDeBoer J and Alan Hallman 2000 Value of pH soil sensor information Paper presented at the St11 International Precision Agriculture conference Minneapolis MN July 2000 Macy Ted S 1993 Macy farms 7 sitespecific experiences Soil speci c crop management proceedings ofthe 1st workshop P 229244 ASNCSSNSSSA Mahajanashetti SB Burton C English and Roland K Roberts 1999 Spatial break even variability for custom hired variable rate technology adoption Selected paper for the annual meeting of the American Agricultural Economics Association Nashville TN Aug 8111999 Malzer Garv L Date unknown 199 The changing technology of variable rate fertilizer application Unpublished document Soil Science Department University of Minnesota Malzer GL PJ Co eland JG Davis JA Lamb PC Robert and TW Bruulsema Spatial variability of profitability in sitespecific management Precision agriculture proceedings of the 3rd international conference June 2326 Minneapolis MN p967975 ASACSSNSSSA Mann John 1993 Illini FS variable rate technology technology transfer needs from a dealer s viewpoint Soil specific crop management proceedings of the 1st workshop Madison WI p 317323 ASNCSSNSSSA Marks Robbin S and Justin R Ward 1993 Nutrient and pesticide threats to water quality Soil specific crop management proceedings of the lst workshop P 293299 ASNCSSNSSSA McBratney AB and BM Whelan 1995 Continuous models of soil variation for continuous soil management Sitespecific management for agricultural systems proceedings from the 2quotd international conference March 2730 Minneapolis MN p 325338 ASNCSSNSSSA McBratney AleX B Brett M Whelen James A Taylor and Matt J Pimgle 2000 A management opportunity index for precision agriculture Proceedings of the 51h 31 International Conference on Precision Agriculture and Other Resource Management July 1619 2000 Radisson Hotel South Bloomington Minnesota USA Norton George W Scott M Swinton 2000 Precision agriculture global prospects and environmental implications Paper prepared for the 24 conference of the international association of agricultural economists Berlin Germany August 1319 2000 Nowa Peter J 1993 Social issues related to soil speci c crop management Soil speci c crop management proceedings of the 1St workshop P 269285 ASNCSSNSSSA O Neal Monte R Jane R Frankenberger Daniel R Ess and James M Lowenber Deboer 2000 Impact of spatial precipitation variability on pro tability of sitespeci c nitrogen management based on crop simulation Presented at the 2000 ASAE Annual International Meeting Paper No 001014 ASAE 2950 Niles Road St Joseoph MI 490859659 USA Oriade Caleb A Robert P King Frank Forcella and Jeffrey L Gunsolus 1996 A bioeconomic analysis of sitespeci c management for weed control Review of Agricultural Economics 18 523535 Oriade CA and MP Popp 2000 Precision farming as a risk reducing tool a whole farm investigation Proceedings of the 5 International Conference on Precision Agriculture and Other Resource Management July 1619 2000 Radisson Hotel South Bloomington Minnesota USA Pan WL DR Huggins GL Malzer CL Douglas Jr and JL Smith 1997 Field heterogeneity in soilplant nitrogen relationships implications for sitespeci c management In The state of sitespeci c management FJ Pierce and EJ Sadler eds p 81100 ASNCSSASSSA Pannell DJ and AL Bennett 1999 Economic feasibility of precision weed management is it worth the investment In Precision weed management in crops and pastures Eds RW Medd and JE Pratley RG and FJ Richardson Melbourne httpwwwgeneraluwaeduauudpanneldpap99031htm Babcock and GR Paustch 1999 Modelbased technique to determine variable rate nitrogen for corn Precision agriculture proceedings of the 4th international conference July 1922 p 12791289 ASNCSSNSSSA Pierce Francis J and Peter Nowak 1999 Aspects of precision agriculture Advances in Agronomy 67 185 Popp J and T Grif n 2000 Adoption trends of early adopters of precision farming in Arkansas Proceedings of the 5Lh International Conference on Precision Agriculture and 32 Other Resource Management July 1619 2000 Radisson Hotel South Bloomington Minnesota USA Rejesus Roderick M and Robert H Hombaker 1999 Economic and environmental evaluation of alternative pollutionreducing nitrogen management practices in central Illinois Agriculture Ecosystems and Environment 75 4153 Robert Pierre Scott Smith Wayne Thompson Wally Nelson Dennis Fuchs and Dean Fairchild 1989 Soil speci c management Unpublished document University of Minnesota Roberts Roland K Burton C English and SB Mahajanashetti 1999 Hypothetical example of evaluating economic bene ts and costs of variable rate nitrogen application Paper presented at the annual Meeting of the Southern Agricultural Economics Association Memphis TN January 80 February 3 1999 Sawyer JE 1994 Concepts of variable rate technology with considerations for fertilizer application Journal of Production Agriculture 7 195201 Schmitt Michael and Dean Fairchild 1991 Variable rate fertilizationcan the technology pay for itself Unpublished document Department of Soil Sciences University of Minnesota St Paul Minnesota Schnitkev GD JW Hopkins and LG Tweeten 1996 Precision agriculture proceedings of the 3rd international conference June 2326 Minneapolis MN p977987 ASNCSSNSSSA Silsoe Research Institute Date Unknown 1999 Yield mapping and precision farming an appraisal of potential benefits based on recent research and farmer experience Silsoe Research Institute SRI Wrest Park Silsoe Bedfordshire MK45 4hs Tel 01525 860000 Snvder C T 39 J J Havlin and G Klllitenber 1996 An 39 analysis of variable rate nitrogen management Precision agriculture proceedings of the 3r international conference June 2326 Minneapolis MN p989998 ASNCSSNSSSA Sobolik Chris J Alan Dzubak 1999 Evaluation of commercial cotton yield monitors in Georgia field conditions Precision agriculture proceedings of the 41 international conference July 1922 p 12271240 ASNCSSASSSA Solohub MP C van Kessel and DJ Pennock 1996 The feasibility of variable rate N fertilization in Saskatchewan Precision agriculture proceedings of the third international conference June 2326 Minneapolis Minnesota p 6573 ASACSSA SSSA 33 Swinton Scott 1997 Precision farming as green and competitive Paper prepared for the AAENAEREIAMA Workshop on BusinessLed Initiatives in Environmental Management The Next Generation of Policy Toronto July 26 1997 Swinton Scott Stephen B Harsh and Mubrariq Ahmad 1996 Whether and how to invest in sitespecific crop management results of focus group intreviews in Michigan 1996 Staff paper 9611 Department of Agricultural Economics Michigan State University East Lansing MI 1996 httpaoecon lib mm A sp9737rhtml Swinton SM and J LownebergDeBoer 1998 Evaluating the profitability of site specific farming Journal of Production Agriculture 114 439446 Swinton Scott M and Kezelee 0 Jones 1999 From data to information adding value to sitespecific data Precision agriculture proceedings of the 4th international conference July 1922 p 16811692 ASNCSSASSSA Swinton SM and J LowenbergDeBoer 1998 Profitability of sitespecific farming SiteSpecific Management Guidelines Potash and Phosphate Institute Series SSMG3 South Dakota State University Swinton Scott and Mubariq Ahmad 1996 Returns to farmer investments in precision agriculture equipment and services Staff Paper 9638 Department of Agricultural Economics Michigan State University East Lansing June 1996 Swinton SM K Jones NR Miller 0 Schabenber er RC Broo and DD Warncke 2000 Comparison of sitespecific and wholefield fertility management in Michigan soybeans and corn 2000 Proceedings of the 5Lh International Conference on Precision Agriculture and Other Resource Management July 1619 2000 Radisson Hotel South Bloomington Minnesota USA Taylor Randal K Mark D Shrock Naigian Zhang and Scott Staggenborg 2000 Using GIS to evaluate the potential of variable rate corn seeding Paper presented at the AETC meeting sponsored by the ASEA 2950 Niles Rd St Joseph MI 490859659 USA Thompson Wayne H and Pierre C Robert 1995 Evaluation of mapping strategies for variable rate applications Sitespecific management for agricultural systems proceedings from the 2quotd international conference March 2730 Minneapolis MN p 303323 ASNCSSNSSSA Thrikawala Sunil Alfons Weersink Gary Kachanoski and Glenn Fox 1999 Economic feasibility of variablerate technology for nitrogen on corn American Journal of Agricultural Economics 81 914927 34 Watkins Bradlev K Yaochi Lu and Wenvaun Huang 1998 F 39 and environmental feasibility of variable rate nitrogen fertilizer application with cairyover effects Journal of Agricultural and Resource Economics 232 401426 Watkins Hal 1999 Additional analysis tools based on yield data Precision agriculture proceedings ofthe 4Lh international conference July 1922 p 1693 ASNCSSNSSSA Weiss Michael D 1996 Precision farming and spatial economic analysis research challenges and opportunities American Journal of Agricultural Economics 78 1275 1280 Wibawa Winnv D Duduzile L Dludlu Larrv J Swenson David G Hopkins and William C Dahnke 1993 Variable fertilizer application based on yield goal soil fertility and soil map unit Journal of Production Agriculture 62 255261 v v quot 39 NC and DD Ruchhnl 1993 Profitability of farming by soils In Site specifrc management for agricultural systems p 199211 ASNCSSNSSSN Madison WI v v quot 39 Nvle C Richard P Wiolkow ki and Harold F Reetz 1993 Variablerate fertilizer application update and 39 U r 39 quot 39 J J University of WisconsinMadison Potash and Phosphate Institute Monticello 111 W quot 39 NC and RP Wnlkow ki 1994 Grid soil sampling for precision and pro t Unpublished manuscript Department of Soil Science University of Wisconsin Madison WI Modi ed from a paper prepared for the 24Lh North Central Extension Industry Soil Fertility Workshop St Louis MO October 2627 1994 Yadav Satya N 1997 Dynamic optimization of nitrogen use when groundwater contamination is internalized at the standard in the long run American Journal of Agricultural Economics 79 931945 Yule IJ PJ Cain EJ Evans and C Venus 1995 A spatial inventory approach to farm planning Computers and electronics in agriculture 14 151161 35 ANNOTATED BIBLIOGRAPHY1 Ahlrichs John S 1993 Computerized record keeping for variable rate technology Soil specific crop management Proceedings of the lst Workshop p 325333 ASNCSSNSSSA Return to REFERENCES Objective To describe the current state of computer use in farm record keeping as applicable to VRT Methods The author reviews pertinent literature regarding record keeping and database management of fertilizer and pesticide inputs ResultsConclusion One of the authors main concerns for VRT decision management and record keeping is the integration of laws requiring best management practices development of reliable tracking systems development of plant food applicators database construction decision aid software and global agricultural information systems into a paperless ow of data One goal would be to link these factors with mapping programs to better understand spatial relations characterizing individual fields To achieve this goal obstacles that need to be overcome by dealers and consultants include purchase of good software learning how to use software by trial and error and how to charge for services The author provides hypothetical examples of his idealized system using plant food application and weed infestation remedies The authors conclusions were optimistic He states Thoughlag time for implementing VRT will continue because our customers are still struggling with the technology the long term savings in time expenses and inputthat will come with VRTwill be worth the effort A budget outlining at minimum the advantages of computerized record keeping as opposed to traditional pen and paper record keeping would be useful Additionally dealers and agricultural consultants seemed to be the focus of this report not farmers Dealerships and extension agents could promote projects or workshops designed to teach farmers how to use different record keeping software packages Crop various Technology VRT record keeping Region any Ahmad Saeed Raymond J Supalla and William Miller 1997 Precision farming for profits and environmental quality problems and opportunities Paper prepared for the Annual Meeting of Agricultural Economics Association Toronto Canada July 2730 1997 1 Assembled by Dayton Lambert Sitespecific Management Center SSMC Purdue University West Lafayette IN 36 Objective To estimate the economic returns from variable rate application of N and water for corn and to determine the effect of VRTN and water management on nitrate leaching Methods A field comprised of three soil types each with different fertilizer demands yield capacities and nitrate leaching potential was hypothesized Conventional and variable fertilizer and irrigation 39 J 39 were r J C quot 39 N applications were assumed to be applied evenly over the entire field Rates were based on soil tests extension recommendations that determined the optimal amount of N for expected yield For VRT applications N was assumed to be applied to specific grids of the field based on the soil requirements of a grid and yield estimates based on the soil type Economic benefits were defined as returns to land and management net returns over variable costs Fertilizer and water costs were considered the only costs that varied between management practices EPIC was used to compare conventional and variable rate management strategies A 15year growing cycle was assumed ResultsConclusion Corn yield decreased by 46 but water use decreased 59 and N applied decreased by 184 under the VRT management scenario This translated into a 2300 gain in returns per acre per year In the simulation model these returns offset the costs of VRTN and water application Results indicated that nitrate leaching below the root zone also decreased by 157 The authors conclude that corn yield were higher under the VRT management system since N and water was applied at prescribed rates and in a more timely manner then the conventional management strategy thus reducing plant stress According to the authors better timing of N application facilitates reduced N application to all soils Precise irrigation schedules reduce leaching also reducing the amount of N application Return to REFERENCES Crop corn Technology VRTN VRTwater Region Nebraska Akridge Jay and Linda Whipker 1998 Sharper look at the leading edge Farm Chemicals 1616 1215 Return to REFERENCES Objective Results of a survey conducted by the authors is reported The objectives of the survey were to contribute insight to producers which directions precision agriculture dealers are headed as they modify precision agriculture technologies to fit their organizational structure and operations and needs as service providers Methods A survey was sent to 1668 individuals associated with retail agronomy dealerships that provided precision technology equipment or services The survey asked respondents about the services or technologies they provided and the number of acres these services covered Respondent s opinions about the future of these technologies and services were included in the survey as well 37 ResultsConclusion The Midwest represented 78 of 466 dealerships that responded to the survey According to the authors one of the first precision agriculture technologies adopted by producers are yield monitors From this base producers have an option to purchase yield maps and data interpretation services These could provide a foundation for grid based soil maps then variable rate fertilizer recommendations followed by application The survey results are presented below Table 10 Traditional agronomic services provided by respondents Traditional Agronomic Services Offered N 455 Soil Sampling 97 Custom fertilizer application 95 Custom pesticide application 93 Seed 92 Consulting 89 Field mapping 83 Record keeping 62 None of the above ltl Precision Agriculture Services Offered N 453 Field mapping wGIS 87 Soil sampling wGPS 82 Yield monitor analysis 6 1 Yield monitor salessupport 38 Agronomic interpretation 77 1997 data Return to Table Listing 38 Table 11 Projected increases in demand for precision agriculture services by the year 2000 Precision Agriculture Services Projected change in Average Average Price in Provided volume of services Price other units offered by 2000 Chargedacre 1997 Field mapping 4 T from 399 177 175map Field mapping wGPS 10 T from 335 327 3050hr Soil sampling wGPS 7 T from 371 611 1030samp1e13 yrs Yield monitor analysis 13 T from 276 142 30200hr Yield monitor supportsales 10 T from 172 202 1501500unityr 3575hr VRT manual 8 T from 190 4 19 VRT controller driven 14 T from 267 522 23acre 15 7 5ton applied VRT controller driven 15 T from 140 771 Data interpretation 9 T from 349 112 3075hr Single nutrient Multiple nutrient Crop na Return to Table Listing Technology precision agriculture general Region Midwest 39 Akridge Jay and Linda Whipker 1996 1996 precision agricultural services dealership survey results Staff paper 9611 Center for Agricultural Business Purdue University West Lafayette IN Akridge Jay and Linda Whipker 1997 1997 precision agricultural services dealership survey results Staff paper 9710 Center for Agricultural Business Purdue University West Lafayette IN Akridge Jay and Linda Whipker 1998 1998 precision agricultural services dealership survey results Staff paper 9811 Center for Agricultural Business Purdue University West Lafayette IN Akridge Jay and Linda Whipker 1999 1999 precision agricultural services dealership survey results Staff paper 996 Center for Agricultural Business Purdue University West Lafayette IN Akridge Jay and Linda Whipker 2000 2000 precision agricultural services dealership survey results Staff paper 0004 Center for Agricultural Business Purdue University West Lafayette IN Objective To profile the dealershipfield of precision agriculture in terms of services provided types of dealerships regional location acres serviced organizational structure and future directions of precision agriculture as seen by rms Methods An ongoing study examines how dealerships are responding to demands for precision agriculture services To date 8167 surveys have been mailed to dealerships specializing in retail sales of agricultural implements and consulting services across the United States So far 1629 20 storeowners technical consultants or managers have responded Questions included which services dealerships provided service fees how they perceived clientele adoption of precision agriculture technologies and what they saw as being the biggest development constraints in the precision agriculture business ResultsConclusion Results from the 1998 survey appear higher than they do for other survey years since that dealerships known to specialize in precision agriculture were targeted In 1999 the survey was randomized Most respondents 67 i 7 were from the Midwest region The authors categorized dealerships as cooperatives large independents nationwide service providers and small independents lt25 outlets The majority of Midwestem precision agriculture service providers were cooperative 45 and small independent 44 dealerships Table 1 shows the percent of acreage managed under some form of precision agriculture technology between 1996 and 2000 Table 2 compares the percentage of the kinds of traditional agronomic services provided by dealerships Table 3 presents the services in greatest demand by producers A distinction is made between dealerships from the Midwest and other dealerships 40 Table 12 Total acreage under some form of precision agriculture management 1996 2000 MidWestern States Other Sates Acres 1996 1997 1999 2000 1997 1999 2000 serviced None na 76 99 94 291 314 333 lt10000 210 71 53 69 188 179 175 10000 220 265 201 207 182 214 238 25000 25001 300 298 35 293 212 164 111 50000 50000lt 160 29 297 337 127 129 143 Base 566 238 283 276 165 140 126 Return to Table Listing Table 13 Traditional agronomic services offered to producers by industry dealerships 1996 2000 MidWestern States Other States Traditional 1 96 199 1 99 2000 1 96 199 1 99 2000 Services Soil sampling 930 911 894 913 810 746 712 710 Seed 853 835 94 923 750 740 799 771 Consulting 760 822 792 773 670 615 626 665 Record 580 572 477 456 450 391 331 343 keeping Field 360 386 459 493 150 160 180 265 mappingGIS None ofthe Na 17 11 23 Na 95 65 62 above Base 361 405 283 279 204 405 139 129 Not differentiated in report Return to Table Listing 41 Table 14 Breakdown of precision agriculture services purchased by clientele from dealerships 1996 2000 1996 1997 1999 2000 Service Soil sampling wGPS 137 147 119 Field mapping 224 3 13 229 Field mapping wGIS 188 79 114 99 Enhanced seed 188 267 390 VRT seeding 18 VRT seedingGPS 07 VRTManual 153 111 134 VRT controllersingle 128 57 91 78 VRT controllermultiple 53 52 47 Yield monitor salessupport 185 143 117 154 Base 470 295 165 225 Return to Table Listing The most recent conclusion of this fiveyear study offered by the authors is though there is much interest in precision agriculture and that this enthusiasm is likely to continue dealerships do not foresee expanding their precision agriculture service base Respondents anticipate that the demand for precision agriculture services will grow within the next three years The authors39 suggest that the precision agriculture technology composite is better suited to the Midwest than other regions of the United States because of the kinds of cropping programs and faim sizes in the region They also estimate that adoption rates will be highest amongst cooperatives and larger national dealership chains Anonymous 1996 Grids value for beets The Sugar beet Grower February 1996 p 1415 Return to REFERENCES Objective The report summarizes grid soil testingvariable rate fertilizer application research results from a university The objective of the study was to l to determine the nitratenitrogen soil pro le of a sugar beet field to a maximum depth of four feet 2 to compare economic returns of gridbased variable rate fertilizer application with conventional fertilizer application methods and 3 to continue this study over a period of years to explain nitratenitrogen changes in the field over time 42 ResultsConclusion Grid soil sampling results ranged from 45 to 144 lbs of nitrate nitrogen per acre Conventional soil testing techniques where probes are assigned randomly to points in a eld resulted in a fieldwide average of 117 lbs of nitrate nitrogen per acre Grid samplingvariable rate fertilization generated a net return of 48 more per acre than the conventional fertility management strategy Grid sampling and soil test costs were 1273acre compared to the 068acre cost of the conventional soil sampling method Variable rate fertilizer application was priced at 900acre whereas the conventional fertilizer application method was 350acre Gridbased soil test results called for an additional application of 4llbs of nitrogen adding 820 The total cost for the grid samplingvariable rate application method was 2575acre The gross income per acre under the VRTN strategy was 74acre with a net return of 4825 The author concludes that returns will vary depending on the spatial variability of nitrogen throughout the eld RETURN TO INTRODUCTION Crop sugar beets Technology grid samplingVRT Region Minnesota Atherton BC MT Morgan SA Shearer TS Stombaugh and AD Ward 1999 Sitespecific farming a perspective on information needs benefits and limitations Journal of Water and Soil Conservation 2quotd Quarter 1999 Return to REFERENCES Objective To identify the kinds of information needed to practice sitespecific farming Traditional and new data collection techniques are discussed in terms of future needs that will arise as precision agriculture develops Methods The authors use personal experience and additional reports to describe the components of sitespecific management especially in terms of data collection and information management ResultsConclusion The authors list the main factors in uencing yield variability Soil factors include moisture content nutrient load pH topsoil depth cation exchange capacity texture and mineral composition bacteria and other organisms and air Management decisions affect the health of soil hence plant growth Knowing the extent to these factors spatially vary across a field provides producers with an interrelated series of information upon which informed fertilizer management recommendations can be made Topography such as relative elevation slope and landscape position in uences the physical properties of soil Less organic matter and thin topsoil depths are correlated with slope Lowlying areas drain poorly and often have higher levels of organic matter Yield is affected by the topographical spatial variability Elevation and slope have accounted for 4984 of within field yield variability in wheat Climatological factors in uence the kinds of crops that can be grown in a region along with plant disease pathogenesis and irrigation and drainage needs and accounts for much of the seasonal variation in yields Climates directly affects soil moisture content hence yield Plant stress caused by excess water explained 69 of yield variability in an Iowa field 43 Climatological effects are best understood by compiling seasonbyseason data Pests including insects plant pathogens and weeds are responsible for approximately 37 of preharvest crop losses An Iowa study documented returns of 458 when herbicides and pesticides were used with corn However pests can display spatial variability across a eld Managing pests at threshold levels in speci c areas are an alternative to whole eld application of herbicides or pesticides Integrated pest management is another form of VRT in that pesticides are employed when the bene ts of spraying are greater than application costs Cultural practices include plant population density planting dates row orientation and dates of plant maturity Yield maps provide a tool for tracking plant population growth cycles and can link yield variability and speci c growth stages to eld variables Data can be collected manually or automatically Manual collection such as soil sampling and scouting can be time consuming and labor intensive Onthe go data collection techniques employ GPS and yield monitors and can be adapted to other farm management operations such as soil sampling and elevation mapping Remote sensing has much potential yet little information exists about its economic feasibility Remote sensing can provide whole eld information When used with GIS wider off farm contexts affecting yield variability can be discerned providing the producer a composite of information from which sitespeci c as well as whole farm management decisions can be made Obstacles impeding adoption of remote sensing include specialized instrument calibration the indirect subjective nature of the data generated limited enduser control and the image acquisition time lag The authors conclude that there is currently no global uni ed set of information characteristic of sitespeci c management Information selection will be based on collection costs the timeframe the information is valid the utility of the data in estimating yield and its ability to reduce environmental risk Crop any general Technology VRT general description Region United States Audsley E 1993 Operational research analysis of patch spraying Crop Protection 12 111119 Return to REFERENCES Objective To simulate the economic returns generated by controlling weeds using variable herbicide patch spraying Questions asked include at what weed population density economically warrants herbicide application And is it more pro table to spray an entire eld at one scheduled time or spray weedinfested sections as needed Methods The model assumes that although weed patchiness can be caused by a number of factors mainly anthropogenic weed seedbank density in one patch is independent of weed populations in other patches Weed biological characteristics used in the model include the number of weeds that successfully reproduce seed viability and longevity plant fecundity and germination time and rate Other model parameters include herbicide cost herbicide kill rate patch size and cropweed competition for space A 44 time period of ten years was simulated Spray strategies compared were patch spraying and whole eld spraying ResultsConclusion The most obvious advantage of patch spraying is that herbicide is not wasted on weedless portions of the eld Weed competition had little effect on the feasibility of patch spraying Overall costs of the two methods were not sensitive to a plant density threshold per m2 However patch spraying is not pro table at extremely high weed seed densities or where there are large weedy patches Herbicide ef ciency also determined whether patch spraying was economically ef cient Patch spraying is more pro table with more effective herbicides Crop na simulation Technology VRTweeds Region UK Babcock Bruce A and Gregory R Paustch 1998 Moving from uniform to variable fertilizer rates on Iowa corn effects on rates and returns Journal of Agricultural and Resource Economics 232 385400 Return to REFERENCES Objective To determine the value of variable rate technology compared to conventional singlerate N applications in economic and environmental terms Differences in yield profits and N use are projected for individual elds and extrapolated to include counties as producers switch from singlerate N application to VRTN The authors used data from previous studies to determine model parameters Methods The authors randomly select 240 sites from 20 locations representing 12 counties Management histories of each site along with yield potentials were used as guides to fertilizer application rates in the model Yield potential was correlated with soil maps Using this information a model was designed to analyze the environmental and economic costs and bene ts absorbed by producers if they switched from singlerate N application to VRTN ResultsConclusion The value of VRT is not viewed in terms of yield increases and input savings Rather VRT is a method to avoid N misapplication over an entire eld This distinction provides both production and environmental bene ts by correcting N soil overloading and waste As the price of N fertilizer increases so does the value of VRTN The converse is equally true Simulated results were generated after ltering data from 20 randomly selected sites representing 12 counties through the model Findings suggest that 66 of the acreage farmed using singlerate N application would be oversupplied with nitrogen 4 would be undersupplied while 30 would receive optimal amounts If farmers were to switch from singlerate technology to VRT gross returns would increase 403 range When all counties were combined returns over fertilizer cost were 444acre Increases in returns were mainly due to decreases in N application When producers are unable to vary fertilizer rates or they lack information where the bestyielding soils are located in a eld then they have reason to fertilize the highest 45 yielding soils even if it is not necessary In contrast producers using VRT reduce production costs by decreasing amounts of fertilizer applied The 444acre increase in returns using VRT instead of a single rate application may be overestimated The values presented by the authors do not include the costs of switching over to VRT The authors estimate the costacre of VRT to be 150 According to their figures subtracting this value from the gross returns the minimum and maximum returns are 002 and 182 respectively with a range of 180 Still according to their model VRT is cost effective Whether or not these benefits can be realized remains to be determined from field trails and further analysis Crop corn Technology VRTN modeling Region Iowa any Bamhisel RI MJ Bitzer JH Grove and SA Shearer 1995 Agronomic benefits of varying corn seed dpopulations a central Kentucky Study Precision agriculture proceedings of the 3r international conference June 2326 Minneapolis MN p957966 ASNCSSNSSSA Return to REFERENCES Objective To investigate the economic feasibility of varying seeding rates according to soil depth and to compare yields when planting density is varied according to soil type to conventional seeding strategies where seed is planted based on plant population density Methods Three seeding rates were evaluated 45 75 and 70 Kha Two constant seeding rates were checks 49 and 64 Kha Soil tests were used to determine soil fertility and topsoil depth Samples were taken at three different depths from 0 to 20cm below the surface For each treatment seeds at rates prescribed based on topsoil depths lt15 1520 20lt cm were planted in 3m wide strips Economic results were based on 11000 seeds and 300bu corn ResultsConclusion Corn yield on topsoil less than 15cm deep was greater for low planting density treatment than they were for the seeding rates The converse was true for deep 20lt cm topsoil profiles where higher seeding rates generated higher yields Varying seeding rates according to topsoil depth produced more com than constant seeding rates Net returns for variable seeding were higher 77160ha than they were for conventional constant seeding rates of 49 and 64 Kha 72000 and 69100 respectively The authors caution that their results may be only applicable to Kentucky corn farming as the topography lends itself to rolling hills were farms are usually located on upland sites and highly variable soil depths Crop corn Technology VRTseeding Region Kentucky 46 Bauer Troy A and David A Mortensen 1992 A comparison of economic and economic optimum thresholds for two annual weeds in soybeans Weed Technology 61 228235 Return to REFERENCES Objective To produce a model that estimates the economic optimum threshold for controlling nuisance velvetleaf and sun ower populations in soybean crops Methods A simulation model iterated for 15yrs was developed to determine the economic differences between continuous and variable spray management strategies for controlling weed populations in soybean production elds The model was based on the biology of velvetleaf seed ageclass and longevity germination rates fecundity growth rate the number of seedling surviving to reproduction and seedbank survival following tillage or other mechanical or chemical field manipulations The economic model assumed a linear decline in soybean production with increasing velvetleaf population densities A soybean yield function with and without weeds was derived Economic returns were a function of the crop yield function crop price variable purchased materials fuel repairs and maintenance rent and operating expense interest and fixed machinery purchases real estate taxes interest on land costs overhead and management labor costs and herbicide cost The simulation compared an annual continuous spray management strategy to an economically optimal threshold spraying strategy The latter approach recognized yeartoyear variability in weed populations With this expectation more or less herbicide can be applied depending on estimated weed densities for a given year ResultsConclusion The economically optimum threshold EOT weed management approach was superior to the continuous spray management approach Over a 15yr period returns per hectare per year for the EOT strategy were 11945 whereas returns for the continuous spray strategy was only 251 Crop soybean Technology VRT weeds Region Nebraska Beuerlein Jim and Walter Schmidt 1993 Grid soil sampling and fertilization Agronomy and Technical Report 9302 Ohio State University Return to REFERENCES Objective In this extension publication the authors outline the benefits of grid soil sampling and describe in detail field trail results using different grid sampling techniques and grid sizes A partial budget is used to determine the profitability of grid soil sampling compared conventional soil sampling methods Methods In this extension publication the authors compare different grid soil sampling strategies to determine element NPK values in a 144acre field Soil samples were taken at 60 120 180 and 200foot intervals in 540ft straight lines The costs for each strategy were determined Tests determined what appropriate grid sizes should be Once grids 47 sizes were determined three dimensional fertility zone maps were constructed Maps indicated the spatial variation of P and K values A partial budget details fertilizer cost differences between conventional and grid soil sampling practices and net returns after prescribed fertilizer rates based on grid soil sampling were applied to crops ResultsConclusion Depending on the sampling distance and the number of samples P concentrations varied 23 to 33le of P per acre The authors pint out that if only one soil sample had been taken the test values would range would be 10 to 63lbs per acre The authors conclude that fertilization programs based on grid sampling might be less profitable for fields where low soil fertility values are widespread Conversely in fields where soil fertility is highly variable returns from grid soil sampling are realizable Preliminary sampling should be conducted to determine appropriate grid sizes Grid size and spacing should be optimal in the sense that they capture the spatial variability of micronutrients testing costs will soar with too many samples but larger grid sizes might mute local areas where nutrient loads are highly variable The authors suggest that grid sampling and prescriptive measures taken can correct a field over time such that it can be managed using conventional practices or uniform application rates Table 15 The effect of soil sampling grid size on the number of samples per 10 acre unit and cost of soil analysis Grid Spacing it Samnlesl 0acres Analysis Cost10acresquot 60 120 24 120 180 13 65 240 8 40 300 5 25 360 3 15 420 3 13 480 2 10 Rectangular 60 x 120 60 300 60 x 180 40 200 60 x 240 30 150 60 x 300 24 120 60 x 360 20 100 60 x 420 17 85 60 x 480 15 75 Return to Table Listing 48 Table 16 Fertilization cost comparisons of grid and conventional methods of soil sampling Costacre Annual cost for 8 years Grid method Soil sampling and testing 100 x 100 grid 326 Corrective fertilizer 2150 Initial precision spreading 156 Annual crop removal fertilizer 1650 Annual fertilizer application 250 Total 4532 Conventional method Annual plus Buildup P and K 3850 Annual fertilizer application 250 Total 4100 Return to Table Listing Table 17 Returns to grid soil sampling after correcting for P levels Sample Original Yield Postcorrection Yield Income difference Soybean Corn Soybean Corn Soybean Corn Avg Buacre Buacre acre A 21 8 47 106 156 60 108 B 47 159 58 179 64 50 58 C 34 122 54 152 1 19 75 97 A B and C represent 12acres areas of lowest and highest and the average of 144 acres respectively Soybeans6bu Corn250bu Return to Table Listing Crop corn soybean Technology VRT grid soil sampling Region Ohio Bongiovanni Rodolfo and James LowenbergDeBoer 1998 Economics of variable rate lime in Indiana Precision agriculture proceedings of the 43911 international conference July 1922 p 16531665 ASNCSSASSSA Return to REFERENCES Objective Using a spreadsheet model the authors determine optimum lime rates for speci c locations in a eld This study ts yield responses to eld data from controlled experiments investigating liming rates The authors ask whether sitespeci c pH prescriptions are pro table over a 4year cycle of soil sampling and if 25acre grids 49 provide sufficient information to achieve this The decision whether or not one should adopt variable rate liming strategies is addressed based on the findings Methods Three liming strategies are compared The first is a sitespecific management strategy SSM using agronomic recommendations The second is SSM using economic rules speci cally that marginal value product must equal marginal factor costs the additional value gained from applying an extra unit of fertilizer must at least equal the application cost of the material added The third analyzed is information strategy This strategy assumed the producer uses agronomic recommendations from university or custom extension services that she has access to gridbased soil test information but does not have the machinery variable rate equipment to mobilize the information Here a uniform rate is applied over the entire field at a rate that will bring an area of the field with the lowest pH up to the desired or recommended level These strategies are compared to whole field management strategies where uniform lime application rates are used over the entire field based on conventional recommendations Doing nothing is used as a control case Additionally a sensitivity analysis examining whether l0acre grids are more effective than 25acre grids when testing soil is conducted ResultsConclusion The results indicate that variable rate application of lime is profitable as a standalone activity The SSMEconomic strategy was the most profitable management option The next most profitable strategy was the SSMAgronomic followed by whole field management then doing nothing Information strategy was less profitable than whole field management because of the large amounts of lime needed to bring the lowest portions of the field up to acceptable rates In the sensitivity analysis returns from l0acre grid were less than 25acre grids because of the extra amount of sampling needed to cover the field However SSM with lime using a 25acre grid is more profitable than whole field management using grids of equal size The data are from mixed sources 18 different states possibly confounding the results by regional effects The study combined regional averages ignoring the possibility that the data set may have been skewed Return to Table 9 Crop corn soybean Technology VRT Region Indiana Bongiovanni Rodolfo and James LowenbergDeBoer 2000 Nitrogen management in corn using sitespecific crop response estimates from a spatial regression model Paper presented at the 5Lh International Precision Agriculture conference Minneapolis MN July 2000 Return to REFERENCES Objective To determine whether yield monitor data is useful for estimating sitespecific crop N response and to compare to techniques for determining corn yield response functions ordinary least squares OLS and spatial autocorrelation regression SAR Yield monitor data was analyzed using spatial regression Following spatial regression analysis of yield monitor data the profitability of sitespecific N management VRT using the above diagnostic methods was determined using a partial budget analysis 50 Pro tability analysis compared returns from variable rate N management to a uniform rate N management strategy The results presented are the rst in a series of studies to be conducted over four growing seasons Methods Data from four farms was collected to estimate N response Variable rate nitrogen treatments were 29 53 66 106 and 1315kgha Three soil types were identi ed based on topography hill slope and low Control strips received no nitrogen treatment A randomized complete block design was used during the trials Within each block treatments were randomized Nitrogen rates were consistent for an entire strip and the highest N rate for each site was higher than the estimated maximum yield level A yield monitor was used during harvest Corn response to N functions was estimated using spatial econometric techniques Brie y this diagnostic technique determines the extent and strength to which different fertility zones are related For example the N value of a fertility zone situated in a lowlying area may be strongly correlated with the Nvalues of a contiguous zone with a slope or higher elevation Additional variables such as rainfall or hydrology will affect the Nvalues of the lower zone because of its location relative to the higher zone Spatial econometrics aims to parse these relations and determine the strength of dependencies between multiple variables Results from this test yields response function coefficients speci c to a landscape management zone The foundations of these response functions are the strength of the relation between the variables de ning that zone slope Nvalues pH water holding capacity Software packages capable of handling such multivariate analyses are currently ArcView and SpaceStat The accuracy of ordinary least squares and spatial autocorrelated regression methods for determining the economic returns from individual production zones were compared especially in terms of the economic feasibility of VRTN ResultsConclusion Preliminary results of the study indicate that the SAR method was more accurate than OLS when determining corn yield response functions Marginal analysis determined economic feasibility of uniform versus variable rate N treatments It is assumed that the added value of the crop gained by adding additional N is equivalent to the application costs of this additional unit Pro ts are maximized when the marginal value product equals the marginal factor cost Returns varied across soil types based on topography zones and according to the regression model used Variable rate nitrogen application was more pro table then uniform rate treatments in all but 5 treatments combining OLSSAR comparisons 95 Return to Table 9 Crop corn Technology VRTN Region Argentina Braga RP JW Jones and B Basso 1999 Weather induced variability in sitespeci c management pro tability a case study Precision agriculture proceedings of the 4 international conference July l922 p 18531863 ASNCSSNSSSA Return to REFERENCES 51 Objective The authors ask the following questions what are the bene ts of precision agriculture how much precision is needed to realize bene ts and what risks are associated with weather variability Based on the last question the authors ask if precision agriculture is only bene cial during good years rather then bad Methods The study site was a hypothetical 60ha eld represented by four soil types Variable rate sprayers were available and cost 900 ha 391 The conventional application rate for the farmer was 180 kg N ha 391 split in two applications A yield function incorporating these parameters was derived The model simulated 35 years of crop production ResultsConclusion Higher grain yields were achieved during better weather years for similar N application rates However combining soil types and weather years did not increase the accuracy of the scenarios studied During the simulation price per unit N was higher for variably applied N which reduced the N recommendation rates resulting in lower crop yields The authors assumed that price drops in N fertilizer would in uence this result Sitespeci c management did not reduce risks associated with weather patterns The time sequence used in the model was not autocorrelated That is the authors assume that N carryover effects could be accounted for if time sequences overlapped with one another instead of being independently distributed Gains net return varied according to soil type An enterprise budget was not included in the analysis perhaps for the simplicity s sake However the authors mention that in order to obtain realistic gures describing the economic feasibility of sitespeci c management an analysis must include detailed breakdowns of farm inputs and outputs along with off farm variables that in uence production Crop corn Technology VRTN modeling Region Michigan Bruulsema TW GL Malzer PC Davis and R Copeland 1996 Spatial relationships of soil nitrogen with corn yield response to applied nitrogen Precision agriculture proceedings of the 3rd international conference June 2326 Minneapolis MN p505512 ASNCSSNSSSA Return to REFERENCES Objective The utility of landscape characteristics and soil attributes as estimators of crop response to nitrogen was examined Corn yields were interpolated to points where soil nitrogen indices had been measured to predict nitrogen response curves No economic analysis was provided Methods Three corn production elds of 5 of 6acres were divided into 5m strips Four to siX strips were used as replicates for each of siX Napplication treatments A radar controlled variablerate applicator was used to apply nitrogen to each strip Differences in eld elevation were determined at each site At each soil sample spot within sites corn yield corresponding to each treatment was extrapolated by estimating corn yields 52 measured in each segment Pro tability was evaluated subtracting yield returns from implementation costs No detailed budget was provided ResultsConclusions Relationships between soil N indices landscape characteristics and yield responses was weaker than expected There were no differences detected between soil nitrogen indices collected in the spring or those that were collected in the fall The soil test with the highest coefficient of correlation was total N A positive correlation was found between elevation higher ground soil photone lighter color and change in crop yield at one of the sites However when nitrogen was considered a general trend was found where production response to nitrogen correlated with lowlying areas of fields The authors attributed stronger yield responses to nitrogen in lowlying areas to field saturation The correlation was stronger between nitrogen and crop yield to soil N indices than to economically optimal nitrogen rates EONR The authors conclude that VRTN profitability will be maximized when yield changes are the primary focus not EONR Crop corn Technology VRTN Region Minnesota Buchholz Daryl D Unknown date Missouri grid sampling project Unpublished document University of Missouri Soil Fertility Agronomy Extension 214 Waters Hall Columbia MO 65211 Return to REFERENCES or Table 9 Objective To outline what procedures used to produce field maps determine field fertility variability worked best during a 3year study examining the efficacy and economic feasibility of variable rate application technology in Missouri Net return to VRTP K is presented in rudimentary partial budget form Methods Soil quality was determined by grid sampling at three sites Grid samples were taken in 330ft intervals 25acres Twelve soil subsamples were taken in a 10ft radius at grid points Results were interpreted as a contour map Yield responses combined with soil test information determined VRTP K application rates ResultsConclusions Compared to conventional uniform P and K treatments VRTP K yielded positive returns at each site At site 1 80acres net returns were 4089acre At this site phosphate was the only element varied Returns to VRT for variable P and K applications averaged 1638 at site 2 82acres At site 3 total gains to varied P and K was and 914 Crop corn Technology VRTPK Region Missouri 53 Bullock Donald G David S Bullock Emerson D Nafziger Thomas A Doerge Steven R Paszkiewicz Paul R Carter and Todd A Peterson 1998 Does variable rate seeding of corn pay Agronomy Journal 90830836 Return to REFERENCES Objective To estimate the economic value of variable seeding of corn Field quality and economically optimal plant density were correlated to determine the distribution of eld fertility zones Methods The authors de ne the economic theory of precision agriculture First a eld is subdivided into management units Each unit is subject to three factors The rst vector included edaphic hydrological and topographical characteristics of the parcel The second vector set includes inputs controlled by the producer such as seeding density or fertilizer rate and application timing The third vector set includes stochastic factors such as weather or market forces Yield responses are determined by a function de ned by these variables The authors evaluate the utility of basing fertilization management decisions on the rst set of characteristics A data set provided by an agronomic company was used in the model ResultsConclusion Sitespeci c economically optimal plant densities ranged from 44000 to 104000 plantsha with a mean planting rate of 67900 plantsha A linear correlation between optimal plant densities and site qualities revealed that site quality was not a good estimator of plant density r 027 However the ndings indicate that where site quality is relatively modest considerably higher plant densities are required to achieve optimality This suggests that not having adequate seed in eld sections of modest quality is a downside risk To determine the economic advantages of variable rate seeding the authors tested four scenarios Each scenario was compared to a uniform seeding strategy In the rst scenario the farmer is assumed to know the yield response of a given location in the eld and can apply the recommended seed rate to that area In the second scenario the farmer does not have the ability to vary seed application yet knows that yield responses vary throughout the field The farmer has the ability to vary seeding yet does not know the fertility variability of the eld in the third scenario In the fourth scenario the farmer does not know the yield responses across the eld nor does he have the capacity to vary seeding These scenarios were tested under four different eld qualities in terms expected yield Mg ha39l When scenarios 1 and 2 were compared VRS was pro table for the farmer capable of varying seed application range 983 to 1283 When scenarios 3 and 4 were compared returns from VRS were slightly greater than those from uniform seeding range 015 to 149 Returns from the value of knowing yield responses under a uniform seeding application protocol ranged from 001 to 006 The authors conclude that at its current stage of development VRS is of little economic bene t to producers VRS would only be pro table to farmers who knew a great deal about the correlation between yield and plant density for each section of a eld Generation of this knowledge entails many years of production data to generate yield response function coef cients speci c to a eld The authors raise some valid points about the costs associated with information gathering and whether those costs will pay for themselves within a given time frame As a standalone practice VRS may not presently be economically feasible 54 Crop corn Technology VRTN Region MidWest Bullock David S and Donald G Bullock 1999 From agronomic research to farm management guidelines a primer on the economics of information and precision technology Forthcoming Precision Agriculture Return to REFERENCES Objective The authors attempt to demonstrate the complementarity between quality information and precision agriculture using a dynamic optimization model with stochastic components Methods As the model is built 39 quot r n n 39 39 factors such as rainfall are included step by step to demonstrate the increasing complexity of the economics of decision making underlying precision agriculture As each component is included in the model the value of information about that variable is revealed For purposes of simplicity the authors posit a hypothetical field with two known soil depths Uniform or variable fertilizer application rates are programmed into the model generating a composite of management options from which farmers representing different risk profrles might choose ResultsConclusions From their model the authors conclude that precision agriculture will not be worthwhile to a decision maker who does not have adequate information The authors define adequate information as perfect information including knowledge of probability distributions for weather patterns external markets or reasonable estimates for expected crops yields It is no surprise to the authors that farmers possess incomplete knowledge about their fields since the main technologies of precision agriculture PA are not readily available to the public economically or otherwise The authors suggest that PA will not take of in the public domain until the conditions that render it economically optimal are determined For now PA will remain in the domain of research and development That farmers do not have access to the tools supporting PA does not necessarily mean that farmers possess relatively little information about their fields Having tools that can finetune the soil profile and chemical composition of a field down to the square foot may generate information useful for answering some questions However whether or not this information has any production value remains in question What needs to be determined is which tools will aid a farmer in the decision making process and in what combinations The combination of technologies will of course be 1 J upon i 39 an 39 39 39 factors such as the risk profile of the individual the history of the farm the region where the farm is located and which crops are grown and when Crop Simulation Technology Simulationdynamic optimization Region NA 55 Carr PM GR Carlson JS Jacobson GA Nielsen and E0 Skogley 1991 Farming soils not elds a strategy for increasing fertilizer pro tability Journal of Production Agriculture 41 5767 Return to REFERENCES Objective To compare crop yields between different soil types within fields and the economic feasibility practicing sitespecific fertility management Methods Fertility zones of four fields having between two and ten soil types were mapped using aerial photography and satellite imagery soil survey reports and producer knowledge of the field Soil tests results for N P and K were based on the average of four core samples taken from 0 to 48in below the surface Recommended fertilizer rates were based on yield goals soil test results from management units as defined by soil test results and university extension guidelines Uniform whole field optimal and site specific treatments were compared with a check treatment no fertilizer Fertilizer rate recommendations for the optimum treatments were based on the information collected sitespecific information averaged and applied as a whole field application Fertilizer was applied in strips using a randomized block design Twenty yield samples were taken from each management zone at harvest ResultsConclusion Highyielding soil types produced two times as much grain than lowyielding soils There were no statistical differences in returns between uniform optimal and sitespecific managed units However the optimal fertilizer management strategy generated 20ha more returns than the sitespecific management treatments Return to Table 9 Crop wheat Technology VRT Region Montana Casaday William W and Raymond E Massey 1999 The growth and development of precision agriculture service providers Precision agriculture proceedings of the 4 international conference July 1922 p 17571765 ASNCSSNSSSA Return to REFERENCES Objective To provide a summary of the precisionagriculture related services and their current prices Methods A survey was to twentyseven agricultural dealerships that offered precision agriculture related services ResultsConclusion The authors conclude that precision farming had evolved as a series of clusters in different areas of the United States Agriculture dealerships serve as hubs providing specialized precision agriculture services Service providers expect that the 56 demand for precision agriculture related technologies would continue to grow especially in the domain of variable rate application technologies Other costs not included in this analysis were lagtime associated with training and learning human capital costs and additional peripheral costs such as computer hardware and software It was also assumed that individuals would hire a consultant to carry out precision agriculture related activities instead of implementing the tasks themselves Table 18 Costs per acre for various PA technologies Technolo y Cost acre 391 Soil Testing and maps 375 1100 Variable Rate Applicator Including Truck 300000 Variable Rate Applicator 15000 20000 Variable Rate Application 100 500 Variable Rate Application lt3 products 100 250 Yield Monitoring Equipment Cost 7000 10000 Yield Maps 025 100 Service Charge 263 407 Missouri 1998 Return to Table Listing Crop na Technology precision agriculture general Region Missouri Cattanach A D Franzen and L Smith 1996 Grid soil testing and variable rate fertilizer application effects on sugar beet yield and quality Precision agriculture proceedings of the 3rd international conference June 2326 Minneapolis MN p1033 1038 ASNCSSNSSSA Return to REFERENCES Objective Three trials conducted over two years investigated field spatial variability of N P and K Variable rate N application VRTN based on soil information collected using grid sampling was compared to uniform N application methods based on whole field soil testing Methods The study sites were three fields ranging from 67 to 90ha Sugar beets were the primary crops in rotation with grains Three depths were tested for nitrateN 015 1660 and 61105cm Grid sizes ranged from 125 to 160ha SiX to eight soil core samples were taken in each grid for VRTN recommendations Recommendations for uniform application rates were based on 30 to 40 core samples taken randomly over across the field Each field was divided into strips Each strip received either a uniform N application or a VRTN application A crude partial budget evaluated the profitability of technology employed ResultsConclusions Not surprisingly grid coil sample results were more accurate than conventional soil testing results Conventional soil testing procedures resulted in 50 to 57 76 of the eld being underfertilized At all sites yield response and sucrose content from VRTN and grid sampling techniques were greater than whole eld soil analysis and uniform N application Subtracting the additional costs of grid sampling and VRTN from the yield a net return of 14300ha was achieved Instead of lumping costs of VRTN and grid sample together it might be useful to present the costs as a line item budget How useful would a microanalysis be when looking at the unsubstantiated reportss of these technologies Furthermore an itemized budget might uncover some costs not foreseen or included in the analysis as presented Some costs not directly associated with VRTN grid sampling might in uence the outcome of the analysis Crop sugar beet Technology VRTN grid soil sampling Region Minnesota North Dakota Clay SA GJ Lems DE Clay MM Ellsbury and F Forcella 1999 Targeting precision agrichemical applications to increase productivity Precision agriculture proceedings of the 4th international conference July l922 p 16991707 ASNCSSNSSSA Return to REFERENCES Objective To compare pre and postemergence herbicide recommendations based on models simulating resources available to producers historical information about previous treatment protocol and other decision based on price rebates and other factors Methods Three trials were conducted on a field under a soybeancom rotation Five treatments were replicated four times using a randomized complete block design Three recommendations generated using a bioeconomic model were compared to a producer s routine herbicide application rate and a rate recommended by the local extension facility ResultsConclusion The herbicide recommendations generated by the model had equal or higher net returns than the conventional treatment of the producer In all cases the strategies proposed by the models were less expensive than the treatment of the producer The results suggest that recommendations based sitespecific information generated by the models when actual field data is used can improve profitability Crop soybean Technology VRT Region Minnesota Colbum J W 1999 Soil doctor multiparameter realtime soil sensor and concurrent input control system Precision agriculture proceedings of the 4Lh international conference July l922 p 1693 ASNCSSNSSSA Return to REFERENCES 58 Objective To evaluate the effectiveness of the Soil Doctor variable application system while providing the theoretical background behind its operation and application An economic analysis is provided Methods A series of yield functions are presented in lieu of soil quality parameters N P and K Nitrogen is used throughout the report as an example ResultsConclusion Field variability yield response curves and average soil nitrogen nitrate levels determine the potential amount of N savings and possible yield increase The authors conclude that the success of any new technology introduced into the agricultural arena depends upon the returns on investment it generates The authors suggest that the success of the Soil Doctor system may in part be due to the high calibration levels recommended to tolerable nitrogennitrate levels by the manufacturers The higher calibration levels mean more N will be applied over a certain area that is detected as being Ndeficient Nonetheless as a variable rate application system N levels are applied as prescribed fertilizer costs are reduced and Nloss to the environment is reduced Basing profitability in terms of yield only this system is economically feasible The authors base their economic study on yield only Other costs such as the costs of maintaining Soil Doctor and training individuals how to operate and care for it are not considered Daberkow Stan G and William D McBride 1998 Adoption of precision agriculture technologies by US corn producers Precision agriculture proceedings of the fourth international conference part B p 18211831 ASACSSASSSA Madison WI Return to REFERENCES Objective The authors present data on the adoption rate of precision agriculture technologies by com farmers The analysis provides a description of the socioeconomic profile of adapters especially early adapters Key mechanisms and sociological attributes involved in the adoption process are eshed out using logit analysis Methods A logit analysis is used to describe the sociological profiles of farmers that had adopted precision technologies specifically grid soil sampling VRT for lime and fertilizers and yield monitoring ResultsConclusions Farmers who had adopted precision agriculture technologies tended to be more educated having completed college and were fulltime falmers compared to nonadopters Debttoasset ratios were also larger for adopters Early adopters also falmed significantly more acreage were more specialized in producing cash grains and made more money from corn sales than nonadopters Logit analysis results indicate that adopters were more likely to keep farm records using computers were less than 50 yrs of age relied on consultants for technical advice and had higher expected corn yields The authors variables used to measure risk debtasset ratio crop and income diversity land ownership were not significant in the logit analysis Although farmers from IL IA and IN were more likely to have adopted precision agriculture 59 technologies especially yield monitors regional variation may have been compromised as data from 16 states 950 different farms was combined Crop corn soybean Technology yield monitors VRT Region Mid West Daberkow Stan G and William D McBride 1998 Socioeconomic pro les of early adopters of precision agriculture technologies Journal of Agribusiness 162 151168 Return to REFERENCES Objective To describe the factors in uencing technology adoption and to present data collected by survey illustrating the extent of adoption of precision agriculture technologies by farmers in the United States A socioeconomic pro le of early and late adopters is provided along with a comparison of farm resource use and allocation differences between adopter and nonadopters A logit analysis is employed to identify key characteristics related to decisions whether to adopt precision agriculture technologies Methods The author conducts a logit analysis to determine the probability that farmers will adopt precision technology specifically grid soil sampling VRT for lime and fertilizers and yield monitoring ResultsConclusion Farmers who had adopted precision agriculture technologies tended to be more educated having completed college and were fulltime farmers compared to nonadopters Debttoasset ratios were also larger for adopters Early adopters also farmed significantly more acreage were more specialized in producing cash grains and made more money from corn sales than nonadopters Logit analysis results indicate that adopters were more likely to keep farm records using computers were less than 50yrs of age relied on consultants for technical advice and had higher expected corn yields The authors variables used to measure risk debtasset ratio crop and income diversity land ownership were not significant in the logit analysis Crop corn Technology precision agriculture general Region United States Daberkow Stan G J FemandezComejo and WD McBride 2000 The role of farm size in the adoption of crop biotechnology and precision agriculture Selected paper for presentation at the 2000 AAEA meetings Tampa FL July 30August 2 Return to REFERENCES Objective To compare the impact of farm size on adoption rates between genetically modified seeds a presumed scaleneutral technology and precision agriculture PA a 60 scalebiased technology The authors conclude that fa1m size is positively related to the ability to innovate Methods A Tobit analysis estimated adoption models for genetically modified GM seeds and PA Data was from the USDA39s 1998 Agricultural Resource Management Study ARMS Variables in the database include farm nancial conditions and management history demographic pro les and farm management and marketing strategies Farmers were asked to what extent they employed alternative production strategies such as GM and PA in their operations PA technologies included grid soil sampling VRT and yield monitoring Variables used in the Tobit analysis included a firm s ability to access credit available human resourcescapital farm location proximity to agribusiness dealerships soilscapes and climactic considerations labor supply land tenure risk preferences education and fa1m structure and size The dependent variable was the percent of farmland managed using either GE andor PA technologies The definition of a quotfarmquot was any business that produced at least 1000 of agricultural goods per calendar year ResultsConclusion For GM seed adoption farmer education and experience location in the Heartland region and farm size were positively related with adoption Tenure as ratio of owned to farmed acres was negatively associated with adoption of GM technology Credit reserves and the ability to access money on a loan basis location in the Heartland region revenue insurance a hedge against risk and farm size were positively related to PA adoption According to the authors the ability to access credit depends on land size and tenure plus other variables The authors were surprised that education was not strongly associated with FA adoption However early adopters rely upon consultants and suppliers as substitutes for personal human capital reserves The authors found that in contrast to the current literature on risk and adoption of PA technologies risk preference measurements as use of revenue insurance was positively related to PA adoption They suggest this indicates early adopters are riskaverse In sum the study concludes that a scalebias exists for both GM and PA technologies but that the bias level is much greater for PA than GM practices Likewise farm size seems to be related to the capacity and propensity to innovate and adopt new technologies Crop any Technology PA and genetically modified seeds Region Midwest Doerge Tom 1999 Yield monitors create on and offfarm profit opportunities Crop Insights Pioneer Intemational 9l4 p l4 Return to REFERENCES Objective To summarize potential on and offfarm profit opportunities presented by adoption of yield monitors The risks associated with the adoption of yield monitor technology are outlined in a unsubstantiated reports analysis Adoption of yieldmonitors is compared to adoption of variable rate technology components 61 Methods The author s discussion is based on personal experience and other refereed sources ResultsConclusion Yield monitoring and mapping provides producers a wholefarm perspective of the overall effects management decisions have on farm operations whereas variable rate technologies provide a fieldlevel perspective As such benefits gained from variable rate technologies are understood best using partial budget analyses On the other hand wholefarm or farming systems analysis is more appropriate for appreciating yieldmonitoring benefits Information generated by yield monitoring can be used over several years providing the producer a foundation for longterm strategizing One problem associated encountered evaluating yield monitor profitability is the subjective nature of the information produced The bias of the interpreter the experience level of the producer and the precision of the map in uence conclusions drawn from map interpretations Benefits from yield monitoring will only be realized when the technology is used concomitantly with other precision agriculture components such as variable rate technologies Yield monitors presently estimate grain moisture content and yield per acre Contour maps representing the spatial distribution of these parameters across a field can be produced by the addition of GPS receiver In turn this package can be retrofitted to other farm implements such as sprayers and spreaders or planters or any other field operation Longterm yield trends can be linked to profit gains or losses within a field The author cautions those considering adopting yield monitor technology A producer must be capable of overcoming a learning curve needs to have the capability of storing retrieving and analyzing voluminous amounts of yeartoyear production data and has to be willing to adapt yield monitor technology to other variable rate technologies such as soil fertility and conductivity mapping soil test lab results crop scouting weed mapping and potentially remote sensing Crop any Technology Yield monitors mapping Region combelt Midwest English BC RK Roberts and SB Mahajanashetti 1999 Spatial breakeven variability for variable rate technology adoption Precision agriculture proceedings of the 4th international conference July l922 p 16331642 ASNCSSNSSSA Return to REFERENCES Objective To develop a model and provide a methodology for determining the minimum spatial break even variability a producer needs for gains from VRT to outweigh implementation costs Especially considered are the roles of crop prices consultant charges and crop inputs Methods Costs of custom hiring precision farming services was estimated to be 467acre The authors used a 30acre hypothetical field Grand total for VRT services was 14010 Corn prices were assumed to be 265bu The authors imagined that two land types 7 high and low yielding characterized the field Returns from uniform and 62 VRT applications were compared relative to different ratios of low and highyielding land types Yield responses for uniform and VRT treatments were estimated using quadratic functions Returns from VRT were calculated by adding the yields generated from low and highyielding land Yield was determined as the product of the corn price and the yield of a land area less the product of the yield of the same land area and the nitrogen price Yields for uniform applications were similarly determined except that total number of cultivated acres and associated yields were used When returns from VRT less returns from uniform application methods were greater than the custom service fees for VRT then the hypothetical farmer was assumed to adopt VRT This determined spatial breakeven variability ResultsConclusion When simulated fields were composed of greater than 30 and less than 85 lowyielding land returns from VRT were positive The authors conclude that farmers will benefit from VRT where fields are typified by these low and highyielding land distribution ratios The results are sensitive to changes in corn to nitrogen price ratios When the nitrogen to corn price ratio is increased by a rise in the price of N the lowyielding land minimum falls 2 percentage points When the ratio was increased by a fall in corn prices the optimal ratio of low to highyielding land did not drastically change ltl high and lowyielding land An increase of 2 percentage points of the minimum amount of land needed in order for VRT to be profitable was incurred when the nitrogen to corn price ratio decreased when a decrease in N prices was assumed The authors assumed a VRT service cost of 467acre or 14010 for 30acre as in their example Ifthis rate were broken down into a line item budget perhaps a more detailed economic analysis could be provided Aside from varying the price of nitrogen in one of their scenarios there were no other stochastic terms incorporated into the model Incorporating such variables is beyond the breadth of the report However larger more sophisticated analysis would have to take factors such as time variable costs discount rates market activities or perhaps even tax incentives in order to better model VRT adoption Crop corn Technology VRT Region Tennessee English Burton C SB Mahajanashetti and Roland K Roberts 1999 Economic and environmental benefits of variable rate application of nitrogen to corn fields role of variability and weather Selected paper for the annual meeting of the American Agricultural Economics Association Nashville TN Aug 811 1999 Return to REFERENCES Objective By changing weather conditions and spatial variability the economic viability of VRT is explored The hypothesis that precision farming provides economic benefits is tested as well 63 Methods The EPIC crop growth model was calibrated to simulate weather conditions corn production and nitrogencrop responses under three different soil regimes and three rainfall patterns The simulation included thirtysix 100acre fields with each with mixed soil profiles Differences in return from variable rate VRT and uniform rate URT N application methods were compared Adoption of VRT was assumed to be 300acre Nitrogen and corn costs were 026lb and 279bu respectively ResultsConclusion All but five of the 36 fields showed positive returns using VRT When rainfall was below average more fields used VRT Twentytwo percent of the fields used URT when during average rainfall scenarios When rainfall was programmed one standard deviation less than expected three more fields would be managed under VRT When nitrogen application rates were restricted returns to fields managed using VRT were greater than those that were not Nitrogen loss to the environment decreased on all simulated fields with VRT Rainfall impacts nitrogen loss carryover affects and the presence of soil nitrogen content during crop growth Although more complex and time consuming instead of using rainfall averages for an entire seasons perhaps rainfall variation over an entire season within a field would produce more accurate simulation data that could then be used in a larger models comparing VRT and URT In addition spatial variation in terms of elevation could be incorporated into such a simulation program Crop corn Technology VRTN model Region Tennessee English Burton Roland Roberts and David Sleigh 2000 Spatial distribution of precision farming technologies in Tennessee Research Report 0005 Department of Agricultural Economics and Rural Sociology University of Tennessee Knoxville February 2000 Return to REFERENCES Objective To identify the current distribution of precision agriculture technologies used in Tennessee which crops are commonly managed using precision agriculture technologies and to describe the adoption trends associated with these use patterns Methods A survey was used to gather information about use of precision agriculture technologies in 95 counties in Tennessee Precision farming was defined as any technology that aided producers l in the collection of information used to identify field variability 2 in making decisions about variable fertilizer application rates in a field and 3 in variable application of fertilizers Other information collected during the survey included the number of farmers using precision agriculture technologies in each county the kinds of technology used the crops and acreage managed by these technologies and the increase in precision agriculture usergroups between a given time period 1 year 64 ResultsConclusion Survey results indicated that 284 farmers used at least one component of precision farming technology This is less than 05 of all farmers in Tennessee and slightly more than 1 of the farms with annual incomes more than 10000 Yield monitors were the most common precision farming technology used by respondents 36 of the 95 counties Of the counties using yield monitors 62 used GPS related technologies as well Grid sampling was practiced at some level by framers in 29 of the counties Grid sampling was practiced concomitantly with yield monitoring 89 in counties with yield monitors Variable rate technology was not as common as yield monitoring and grid sampling activities Results indicated that farmers in 18 of the counties using precision agriculture technologies practiced variable rate application as well Precision agriculture technologies were most commonly associated with corn 55420 acres followed by soybean 54050 acres cotton 18560 acres and wheat 21150 acres The authors suggest that the number of farmers using precision agriculturerelated technology will be 3 with a total of nearly 8 of total crop farms by 2004 if current adoption rates continue Crop corn Technology precision agriculture general adoption rates Region Tennessee Fairchild D and M Duffy 1993 Working group report In Sitespecific management for agricultural systems p 245253 ASNCSSNSSSN Madison WI Return to REFERENCES Objective To summarize the economic components that should be included in any analysis of new farming technologies especially those associated with precision agriculture ResultsConclusion There is no empirical data presented in this report as it is a review The authors generalize three economic principles to be considered when understanding pro tability in the farm context marginal unsubstantiated reports analysis partial budgets and whole farm planning The first analysis examines the point at which the marginal cost of the input equals the marginal revenue As an example fertilizer should be applied until the last unit spent returns an additional unit of output Cost increases and decreases of adopting a new technology need to be itemized Then revenue increases and decreases are evaluated When cost decreases in addition revenue increases are greeter than cost increases and decreases in revenue then the activity is profitable Whole farm planning analysis should be when a new practice will completely alter the farm structure for example converting corn fields to fish ponds Other factors to consider include risk management skills time scales discounting and opportunity costs human capital and offfarm costs and benefits Crop na Technology economic analysis of new technologies Region na 65 Farm Industry News 2000 How to access precision agriculture technologies Internet document wysiwyg3httpserViceindustryclickcomspecialsectionstorycfmvocagcampid83 Return to REFERENCES Objective This internet document outline a stepwise plan of action for adopting PA technology in today s marketplace ResultsConclusion One of the interviewees concludes that entering the PA technology is dif cult since commodity prices are low and producers investment behavior is geared toward shot term pro ts Innovation would have to be in line with cash ow plans to expand production operations and changes in overall farm business plans The interviewee recommends that producers rst acquire yield monitors equipped with GPS followed the next season by a GPS guidance system then VRT technologies A scenario is provided describing the above stepwise adoption process If a comsoybean producer who farms 2000 acres purchases a yield monitor for 7000 and increases yield by l bu acre by conducting variety comparisons the investment will be paid off in one season Other pest or drainage problems might be solved as well increasing further the bene ts Crop mainly corn soybean Technology PA summary Region Primarily Combelt Feinerman Eli and Eshel Bresler 1989 Optimization of inputs in a spatially variable natural resource unconditional vs conditional analysis Journal of Environmental Economics and Management 17 140154 Return to REFERENCES Objective To expand upon methods used to determine the economic feasibility of spatially variable elds using a stochastic optimization approach The authors focus on water as a limiting resource in irrigation systems Methods Variables of import in this report are yield information use and diminishing returns The stochastic optimization model assumes that variable parameter estimates are random Two scenarios are examined within the context of irrigation constrained by a limited water supply 1 conditional economic optimization and 2 an unconditional or quotclosedform solutionquot to the conditional optimization scenario Scenario 1 assumes that the variables of interest in the model are autocorrelated In contrast to the unconditional analysis Scenario 2 the variables of interest are not assumed to be independent of one another and the probability density functions associated with each parameter estimate are not stationary Probability distribution functions for scenario 1 are derived from speci c points in a eld not from a eld average Actual eld measurements are used during the analysis not generalized probability distribution functions This effectively reduces the uncertainty caused by stochastic effects correlated with eld spatial variations The probability a producer will use eld data information ef ciently is thereby increased 66 The two scenarios are evaluated in terms of which model best describes efficient use of information by a decisionmaker ie a farmer who decides where when and what amounts of water should be supplied to a speci c area of a eld given a set of constraints A check model was compared to the conditional and unconditional models It assumed that the producer had perfect information For the analysis a hypothetical spatially variable irrigated field growing corn was used to test the above scenarios A com response function from another report was used during trial runs ResultsConclusion Yield variance was less with the conditional model meaning risk was minimized when information was based on the assumption sample point proximity directly affected the degree to which test values were correlated Both models were sub optimal in terms of net returns from water use compared to the check model The conditional model utility value for water use was 05 lower than the check model whereas the value for the unconditional model was 10 below the control value The authors conclude that by assuming variable autocorrelation yield variance is reduced Reduction of yield variance decreases the riskiness involved in making a decision According to the authors the conditional approach optimizes a body of information and re ects more efficiently a given state of reality during simulation The question remains for the authors how much information is enough Return to INTRODUCTION Crop corn Technology VRTirrigation Region Israel Fiez Timothy E Baird C Miller and William L Pan 1994 Assessment of spatially variable nitrogen fertilizer management in winter wheat Journal of Production Agriculture 71 8693 Return to REFERENCES Objective To determine the optimal amount of nitrogen needed to produce a unit of grain in a field of variable fertility and to estimate the economic value of variable rate nitrogen application based on landscape position as a guideline for dividing a field into units of equal fertility Methods Five nitrogen rates 0 50 75 100 and 125 lb Nacre were applied over four different topographic profiles footslope Sbackslope shoulder and Nbackslope Treatments were replicated four times at each location using a randomized block design Soil from each landscape was sampled prior to the experiment Crop rotations were spring lentils winter wheat and spring peas After harvest Nloss was determined ResultsConclusion The authors conclude that spatially variable nitrogen recommendations must based on yield potential estimates the amount of nitrogen needed to produce one unit of grain at optimum yield and the amounts of residual nitrogen in the soil The economic benefits of variable rate nitrogen application VRTN occur by limiting areas of over and underfertilization in a field The scale of these benefits 67 depends on the actual amounts of misapplied fertilizer during a singlerate treatment and the yield responses attributed to misapplication Three important factors have to be considered Information about yield potential unit nitrogen requirement residual N and N mineralization are needed for accurate recommendations Two elds with highly variable fertility mosaics should benefit more from VRTN since the probability that under or overfertilization is greater with uniform N application practices Last fields where yields slightly decrease or increase following N overapplication or when yields fall dramatically after N underapplication will benefit most from VRTN The authors provide a simple unsubstantiated reports analysis in their report However important factors such as human capital costs of information collection and management fixed and variable costs and opportunity costs were not identified It is unknown whether the figures used to compare the treatments included these components Return to Table 9 Crop beans wheat Technology VRTN Region Washington Finck Charlene 1998 Precision can pay its way Farm Journal MidJanuary 1998 p 1013 Return to REFERENCES Objective To summarize the results of an ongoing study examining the profitability of sitespecific farming Methods A 1300acre farm was divided into three primary management zones based on soil type A uniform application rate served as the control The second treatment integrated sitespecifrc management strategies with manual application techniques The last treatment used GPS integrated with sitespecifrc hardware and software to automatically distribute fertilizer at prescribed rates according to soil fertility Maps were used in the second and third treatments Detailed partial budgets were used to evaluate the profitability of VRT 68 ResultsConclusion Input reallocation was primarily responsible for increased revenue in both variable rate treatments Matching inputs to soil types weatherproofed lighter soils for high temperatures and drought and prepared the more fertile soils to produce above estimated yield potentials However yield increases were more consistent with lighter soils than they were for heavier soils Heavy soils covered 91 of the eld There were little to no yield increases in these zones However savings from applying less fertilizer to the high fertility zones generated positive returns Table 19 Reported net returns comparing GPS and manual application strategies Treatment Standard Manual GPS Average net return 30543 32269 31934 3yrs cornsoybean acre Advantage over 1726 1391 standard rate acre Average net return 27945 29857 29910 3yrs corn acre Advantage over 1912 1965 standard rate corn acre Average 3year corn 151 163 166 yield buacre Corn yield advantage 12 15 over standard rate bu acre Average 3year soybean 53 55 54 yield buacre Annual Technology and Equipment Costs Corn Soybean Manual treatment 1 0 03 acre 1 83acre GPS treatment 1 894 acre 3 82acre Yield monitor alone 133acre Yield monitor with GPS 332acre Significant at 5 level Significant at 10 level RETURN TO INTRODUCTION Table Listing or Table 9 Crop corn soybean Technology VRT Region Illinois 69 Finck Charlene 1997 The learning curve Farm Journal MidFebruary 1997 p 67 Return to REFERENCES Objective To describe a case study situation about the quotlearning curvesquot associated with the adoption of new technologies into extant farming operations Methods The author uses farm manager testimonial recounting their experience learning how to use GPS guidance and maps during variable rate fertilizer application ResultsConclusion According to the operator it took one season to quotwork out the bugsquot of the entire system The system included GPS guidance a laptop computer and mapping software Once problems were worked out the operator felt empowered knowing that unfamiliar quothightechquot hardware and software could be apprehended then applied to his operations Increased returns from the integrated GPSmapping system further reaffirmed the operator s enthusiasm for the new technology Crop corn soybeans Technology VRT Region Illinois Fixen RE and HF Reetz Jr 1995 Sitespecific soil test interpretation incorporating soil and farmer characteristics Sitespecific management for agricultural systems proceedings from the 2quotd international conference March 2730 Minneapolis MN p 731743 ASNCSSNSSSA Return to REFERENCES Objective To provide an alternative to methods conventionally used to interpret soil maps The author argues that fertilizer recommendation rates need to be site farm specific rather than general ie recommendation rates provided by extension services A software program that personalizes soil profiles by focusing on optimization of long term profitability is introduced Methods The model used yield and soil test data from an ongoing USDA corn and soybean production study Grid sample data was used to make soil maps representing four soil types Soil test and pH varied considerably across soil types ResultsConclusion By dividing the average historical yield for each soil type by the predicted relative yields generated soil yield potentials The authors found that whole field management practices had decreased soil fertility of the potentially most productive soils This resulted in the most productive soils yielding no more than the least productive soils in the field The authors conclude that sitespecific interpretation must include soil characteristics and farmer management preferences based on management history Additionally sitespecific management may increase yield variability by augmenting yield of already highly productive areas Lastly information feedback and 70 data management will improve the accuracy of sitespecific management information hence its efficacy over time No enterprise budget was presented in the analysis Although probably justified by yield data inclusion of information such as soil test costs and estimated returns from implementing prescriptive measures from this information would strengthen the authors argument that conventional management methods had decreased soil productivity Crop corn soybean Technology VRTfertilizer N P Region Iowa Forcella Frank 1993 Value of managing withinfield variability Soil specific crop management proceedings of the lst workshop Madison WI p 125132 ASNCSSNSSSA Return to REFERENCES Objective To highlight the basic concepts in uencing the decision whether of not site specific management of withinfield variability is cost effective Methods Eleven 10 ha hypothetical fields were programmed to have varying degrees of field variability soil characteristics Each field was divided into 10 sections Sections either had one soil characteristic while other grids did not Binary codes were used to distinguish these differences From here a field variability index was made Fields with more variability required different amounts of N fertilizer Misapplication costs were calculated Corn yield response to N fertilizer was assumed to be linear with a plateau at lOOkgha ResultsConclusion VRT is most effective when soil profile variability is greatest in fields The type of fertilizer applied to fields will also determine cost effectiveness of soil specific management For example if inexpensive fertilizers are used it may be more cost effective to apply the material uniformly throughout the entire field instead of paying for information yielding field variability and extra costs associated with variable application According to the author the converse holds true with expensive compounds Variable application of expensive materials may be economically justified after information collection and application costs are considered This simplistic model could be improved by adding additional variables The author states that one of the shortcomings of the model is that it cannot consider extemalities associated with fertilizer or pesticide runoff Nor does it consider information collection costs costs that might be saved because of carryover effects or costs cleared by positive returns from production Crop all Technology VRT modeling Region any 7l Fountas Spyridon 1998 Market research on the views and perceptions of farmers about the role of crop management within precision farming Master of Science Thesis Silsoe College Cran eld University httpwwwsilsoecran eldaculdcpfpapersspyridon Fountasindexhtm Return to REFERENCES Objective To understand farmer perceptions of the role of crop management within precision agriculture Producers using and not using precision farming technologies were interviewed As this is a demographic pro le of user groups no formal economics on the pro tability of speci c PA technologies is provided Methods Postal questionnaires were mailed to producers General descriptive statistics report the results ResultsConclusion Survey results indicated that 15 of the respondents used some combination of precision agriculture technologies Users were satis ed in terms of their expectations about the technology being met Reasons why producers had not adopted PA techniques included the high investment costs variable results and minimal agronomic support and technical advice Consumer groups agromachinery suppliers and manufactures and PA experts would accept involvement of an agrochemical company in the development and promotion of PA technologies Crop mixed Technology PA summary demographic pro ling Region UK Godwin RJ IT James JP Welsh and R Earl 1999 Managing spatially variable nitrogen 7 a practical approach Presented at the Annual ASEA meeting Paper N0 99 1142 2950 Niles Road St Joseph MI 490589659 USA Return to REFERENCES or Table 9 Objective To evaluate two methods to determine VRTN application rates The rst method produced sitespeci c yield response functions the second approach employed historical eld data to determine optimal N rates The goal of these objectives is to nd the optimal N rates for low and highyielding portions of elds This would entail increasing N rates in highfertility zones while decreasing rates in lowfertility zones The authors conduct a rudimentary partial budget analysis to determine the economic feasibility of each approach Methods Three sites all with a cropping history of continuous wheatbarley and all with different soil pro le characteristics were used in the experiment Yield maps spanning three years referenced each site and macro and micro soil nutrient levels were determined to identify soil fertility variability Two soil series characterized the rst site while three series characterized the other sites An experimental design was developed that could be replicated at a low cost by farmers as opposed to randomized small 72 blocks Fields were dived into a series of strips with widths that matched farm machinery Widths at each site varied since producer equipment varied Two treatments were compared uniform URT and variable VRT N rate treatments For URTs different N rates were applied evenly along each strip For VRT treatments low medium and high fertility zones were identified in each strip Highyield zones received 30 more N than averagefertility zones while lowfertility zones received 30 less than averagefertility zones Rates were based on historic yields A response function was used to determine the most economic rate of N MERN and the N rate for maximum yield NMAX ResultsConclusion As expected results varied between sites and maximum yield was obtained using different N rates based on soil fertility values within sites The authors attribute variability of net returns to climactic conditions as well Economic returns between all sites were superior to URT treatments range 5 to l3ha Crop wheat barley Technology VRTN Region UK Grif n Terry Caleb Oriade and Carl Dillon 1999 The economic status of precision farming in Arkansas Department of Agricultural Economics University of Arkansas Fayetteville 1999 Return to REFERENCES Objective The authors discuss the factors in uencing the adoption rate of precision agriculture in Arkansas in lieu of returns generated by precision agriculture practices Methods Arkansas agricultural extension agents implemented a survey tool to determine the extent to which Arkansas farmers had adopted precision farming A case study is presented in the report profiling precision farming in Arkansas An enterprise budgeting technique was used to determine the profitability of precision farming in the case study The case farm owns combines equipped with yield mapping equipment yield monitors onboard DGPS systems and moisture monitors The entire farm had been mapped prior to the study Grid based soil sampling was the preferred soil testing method Yield and returns from the farm used in the case study was compared to statewide yield averages for soybean and rice 73 Table 20 Survey results of PA adoption rates by Arkansas farmers 1998 Survey Rice Soybean Cotton CornWheat Farmers using 35 2 12 35 precision farming technology acreage managed 1 lt1 lt1 0105 under precision farming Three leading 1 Fertilizer 1 Fertilizer 1 Limesulfur 1 Drainage inputs precisely 2 Limesulfur 2 Limesulfur 2 Fertilizer 2 Limesulfur managed 3 Drainage 3 Drainage 3 Drainage 3 Fertilizer Common precision 1 Grid sampling 1 Grid sampling 1 Grid sampling 1 Yield monitoring farming practices 2 Yield monitoring 2 Yield monitoring 2 Variable rate 2 Grid sampling 3 VRT 3 VRT application 3 Variable rate application Estimated time for 10 adoption 3 years 4 years 2 years 2 years 20 adoption 8 years 10 years 10 years 5 years 30 adoption 15 years 15 years Never 10 years Descending order of importance Variable rate fertilizing Return to Table Listing Yield and returns for the case farm outperformed the average stateside farm yields across the threeyear time period However yield and returns were higher on the case farm two years before precision farming technologies were implemented Operators attributed lower yield and return to poor growing conditions Similar trends were evident examining state average production data The authors conclude there is no evidence to support the perception that precision farming reduces risk The authors noted difficulties evaluating the economic potential of precision farming with on farm data Farm managers will commit all their acreage to either whole eld or precision management strategies As such precision farming can only justifiably be analyzed across time Whereas the operators held weather conditions responsible for reduced low yields following adoption of precision farming the authors suggest these reductions might be attributable to learning curve paths The authors suggest that unlike farmers in the Midwest where adoption of precision farming is supported by service dealerships adoption of precision farming by Arkansas producers is mainly driven by selfmotivation Crop soybean rice Technology precision agriculture Region Arkansas Grif n TW JS Popp and DV Buland 2000 Economics of variable rate applications of phosphorous on a rice and soybean rotation in Arkansas Proceedings of the Sth International Conference on Precision Agriculture and Other Resource 74 Management July 1619 2000 Radisson Hotel South Bloomington Minnesota USA Return to REFERENCES Objective To determine the relation between phosphorous and yield on four soils in Arkansas and evaluate the pro tability of VRTP treatments on a ricesoybean rotation system Conditions when VRTP application is successful are summarized Methods An EPICderived model simulated ricesoybean crop yields over a thirtyyear period Simulated data 4000plus data points was modeled using dynamic optimization to represent management choices decisions and applications over a tenyear planning period Pro tability as input costs subtracted from gross revenue was incorporated into the model Enterprise budgets provided investment cost estimations Three uniform application rates URT were compared with VRT rates Three URTphosphorous rates were determined according to soil characteristics Four soil types characterized test elds Three soils were siltloam composites while the remaining type was clay ResultsConclusion Variable rate P application was more pro table than URT treatments when soil was 50 to 75 siltloam composition When the proportion of the eld was between 3 and 97 clay VRT was more pro table than URT treatments In elds where mixture of clay and siltloam predominated returns from VRT were 200acre over a tenyear planning cycle In general VRT was not a desirable management strategy when a single soil type dominated the simulation eld URT was more pro table in elds characterized by homogenous soil types especially siltloam composites However suboptimal P rates adversely affected yield For example when P rates determined for siltloam soils were applied to clay soils rice and soybean yields dramatically decreased Crop rice soybean Technology VRTP Region Arkansas Hammond MW and D Mulla 1988 Development of management maps for spatially variable soil fertility Proceedings of the 39Lh Annual Far West Regional Fertilizer Conference Bozeman Montana July 1113 1988 Return to REFERENCES Objective To develop fertility management zone maps by combining information from P and K soil tests Quantitative accuracy of management zones derived from different soil sampling densities was determined A rough partial budget evaluating the economic feasibility of mapping and sampling methods was conducted Methods Soil samples were taken at 100 200 and 400ft intervals Maps of fertility management zones were created using the data Three fertility categories were used low medium and high Cutoff levels for map contours were based on regional fertilizer recommendation rates for potatoes Fertilizer rates for management zones were based on the average of the soil test result for that management zone published guidelines and 75 personal experience Fertilizer blends including N P K S and Zn were applied to each zone accordingly A crude partial budget evaluated the profitability of these management combinations ResultsConclusion Although the conventional uniform application strategy cost less than the variable application treatment 13300 and 13500 respectively it was inefficient compared to the variable rate strategy since it overfertilized 45 of the 139 acre eld and underfertilized 8 of it In terms of net returns potato yields from this trial reportedly covered the costs of uniform and variable rate fertilizer treatments Crop potato Technology VRT mapping Region Montana Hammond MaX Ward 1993 Cost analysis of variable fertility management of phosphorus and potassium for potato production in Central Washington In Sitespecific management for agricultural systems p 213219 ASNCSSNSSSN Madison WI Return to REFERENCES or Table 9 C39J39 quot To 39 quot the 39 efficiency of application costs associated with variable rate management strategies Methods Soil test data K and P was used to generate fertility management maps representing five zones Three zones were used in the study Variable fertilizer rates were applied to management zones after recommendation rates bases on test values were determined Applications for conventional wholefield management control treatments were based on the average of the soil test results Input costs for each strategy were recorded After harvest yield revenue was compared with input costs ResultsConclusion Production costs increased under the variable rate management strategy but not significantly Cost increase was due to grid sampling sample analysis and data management The author notes that by increasing crop grade benefits of variable rate strategies might outweigh implementation costs Potato yields increased 12 tomsacre resulting in net returns of 75150acre When the overall potato grade is improved 1015acre revenue was realized Where fields average 30 tonsacre this translates into increased revenues of 300450acre Crop potato Technology VRT Region Colorado Haneklaus S D Schroeder and E Schnug 1999 Decision making strategies for fertilizer use in precision agriculture Precision agriculture proceedings of the 4Lh 76 international conference July 1922 p 17571765 ASNCSSNSSSA Return to REFERENCES Objective To evaluate different decisionmaking processes governing variable fertilizer application Methods Soil N and P content were measured Additionally the minimal amount of N available to plants was determined Plant N content was determined by Kjeldahl analysis Results from geostatistical surveys were used to produce digitized soil maps ResultsConclusion The authors conclude that in order to accurately describe the distribution of P N and other essential plant nutrients 10m2 blocks are needed as sample sites Furthermore these smaller block units need to be georeferenced to generate maps that accurately represent eld heterogeneity Georeferencing plots also allows for temporal analysis A cursory economic analysis suggests that VRT reduces kilograms of fertilizerP applied an environmental bene t and fertilizer expenses an increase in profits The table presenting the economic figures is not in partial budget form as it does not consider additional costs associated with VRT Crop oats Technology VRTN Region Europe Harper Jayson K M Edward Rister James W Mjelde Bastiaan M Drees and Michael 0 Way 1990 Factors in uencing the adoption of insect management technology American Journal of Agricultural Economics 72 9971005 Return to REFERENCES Objective To study the adoption process of a capital technology and identify the variables in uencing decisions to apply pesticides Methods A logit model is used to specify adoption patterns of rice producers faced with two management options targeting pest control spraying or use of a sweep net Data were collected using surveys Model variables included age education level farm size and complexity and firm characteristics applied N fertilizer adjacent crops planting date and participation at extension fairs ResultsConclusion The decision whether to adopt sweep net technology was dependent upon the farm manager s education level the amount of neighboring land in pasture the proportion of rice acreage planted to other rice varieties farm location in Texas and extension fair attendance Education was negatively related to adoption of sweep nets More educated managers were less likely to adopt this technology The authors suggest that individuals with higher education see other aspects of their operations more important than spending time using a sweep net Farmers were also more likely to adopt this technology where damaging pests were more abundant Those who attended extension fairs were more likely to use sweep net technology Spraying for pests was 77 signi cantly associated with more variables in the model 13 of 19 than the model used to analyze sweep net adoption 4 Older farm managers were more likely to spray for pests Likewise operations with larger elds employed spray management as well Crop rice Technology pesticide technology adoption Region Texas Hayes J C A Overton and JW Price 1994 Feasibility of sitespeci c nutrient and pesticide applications Environmentally sound agriculture Proceedings of the 2quotd conference April 2022 1994 Orlando FL St Joseph MI Return to REFERENCES Objective This report discusses methods whereby the decision whether to use certain components of precision agriculture speci cally variable rate fertilizer application can be rationally made Speci cally mentioned is the use of GPSGIS technologies Methods Soil type variability was determined on a eld traditionally used to produce corn Historical yields associated with the soil types were retrieved Corn nutrient requirements were estimated based on data collected by the university extension service Local nitrogen fertilizer costs were used in a partial budget analysis Nitrogen application rates were estimated for each soil type Four scenarios were simulated 1 variable rate fertilizer application 2 N applied at the rate expected to produce the highest yield 3 N applied using a weighted average and 4 a weighted average based on lowyielding portions of the eld A crude partial budget was used to evaluate the pro tability of sitespeci c fertilizer management strategies ResultsConclusion Nitrogen costs for scenario 1 8043 were lower than they were for scenario 2 8980 and scenario 3 8051 Nitrogen costs for scenario 4 was lowest compared to the other scenarios 6317 The authors rejected results from scenario four as the parameters from which they were derived were entirely hypothetical The authors caution that differences in returns does not necessarily correlate with the management strategy implemented Return to Table 9 Crop corn Technology VRT Region South Carolina Heiniger RW and AM Meijer 2000 Why variable rate application of lime has increased grower pro ts and acceptance of precision agriculture in the southeast Proceedings of the 5Lh Intemational Conference on Precision Agriculture and Other Resource Management July 1619 2000 Radisson Hotel South Bloomington Minnesota USA Return to REFERENCES or Table 9 78 Objective To determine the lime rates needed for variable rate lime application using gridsampling techniques and determining whether this practice was pro table The authors ask whether pro tability improvements are due to decreased inputs lime increased yields or both of these factors To do so they characterized within eld pH variability using grid soil testing The authors provide a partial budget analysis examining the economic feasibility of VRTlime for corn production in Southeastern US Methods Soil samples were collected from 111 elds that had been limed using variable rate technology l997ha total One hectare rectangular grids were used in both coastalplain and tide water sites to determine soil pH values Corn yield response was determined based on grid test results A simple partial budget was constructed to determine VRTpH pro tability VRT application charges were 2750ton and uniform charges were 2500ton Grid soil sampling costs dealership prices were 700acre Uniform soil sampling costs were priced at 259 acre Costs were not amortized ResultsConclusion VRTpH pro tability was different for coastal and tidal regions Optimal pH levels were generally lower in tidal than coastal regions In the coastal plain region VRT adjusted costs were 3614 while adjusted costs for uniform lime were 3904 In the tidal region adjusted VTR costs were 2674 whereas adjusted costs for uniform application were 2008 The authors conclude when field pH is spatially variable uniform testing will over or underestimate pH values hence application rates Secondly when the average eld pH decreases in relation to the target pH differences in lime requirement estimates increases between uniform and grid sampling techniques This translates into savings when application rates are based on gridsampled results VRTpH was successful in coastal plain regions since there was a reduction in lime applied to elds which helped pay for variable application costs Variable rate application costs become similar to conventional application costs Estimated yield also increased since appropriate pH levels were applied to sitespeci c problem areas In the tidal region higher pH levels required more lime and increased costs associated with grid sampling and VRT application The authors cite three key factors related to the success of VRT liming VRT will be pro table when l led average values of the parameters tested are signi cantly less than target values 2 there is a strong relation between crop yield and then parameters being tested and 3 there exists a penalty in terms of yield andor dollars for both under and overapplication of an input Crop corn Technology VRTpH Region Southeast Heisel T and S Christensen 1999 A digital camera system for weed detection Precision agriculture proceedings of the 4th international conference July l922 p 15691577 ASNCSSNSSSA Return to REFERENCES 79 Objective To describe a digital camera system that can automatically identify weed problem areas in a eld then based on the information provide recommendations as to what course of action ie where pesticide should be sprayed and at what rate should be taken Methods Three control sites were established In each site a color camera was installed The camera was equipped with lters sensitive to different light wavelengths Weed re ectance is a different frequency than crop re ectance Cameras were attached to computers that estimated weed densities in fields Computers were attached to a GPS system ResultsConclusion The apparatus provided an acceptable estimate of weed leaf area per meter compared to manual leaf area measurements However the camera system can count and process weed data much more rapidly than the conventional manual method at a speed of 45 kmhour The authors suggest that this technology would be costeffective when used with high valued crops They also imply that pesticide use can be reduced with this technology Unfortunately although some economic factors are considered in the report they are only stated or implied Implementation costs operating costs and other costs associated with training or maintenance of the equipment are not considered Crop wheat Technology VRTpesticide Region Australia Henessy David A Bruce A Babcock and Timothy E Fiez 1996 Effects of site specific management on the application of agricultural inputs Working paper 96WP 156 March 1996 Center for Agricultural and Rural Development Iowa State University Ames IA 500111070 Return to REFERENCES Objective To develop a crop production model incorporating variability when soil stored and applied nutrients are cumulative Production under uncertainty zero knowledge and known fertility variability are examined Under which scenarios variable rate or conventional uniform fertilizer application programs are suitable is explored Methods Key variables in the model developed by the authors include soil fertility classified as random fertilization rate applied by the producer fertilizer costs and crop price Land is assumed to be uniform except for spatial fertility variability The production function was assumed to be applicable to all pints on the land surface Data analyzed using their model was taken from Fiez et al 1993 Different application rates were 0 50 75 100 and 125 lbacre Landscape positions such as backslope shoulder north backslope and footslope were considered Wheat price was 350 buacre Applied N was assumed to be 31lb Carryover effects were incorporated into the analysis 80 ResultsConclusion Results suggest that sitespecific information is a lowvalue commodity Although the information generated from sitespecific tests have a positive value the connection between this information and production and pro t are not yet clear In their study returns from VRT did not outweigh implementation costs The authors conclude that there will be little incentive for producers to adopt variable rate technology in its current state high costs and unreliable inconsistent results that are often J with 39 J39 39J 39 risk Crop wheat Technology VTR Region Iowa Hennessey David and Bruce Babcock 1998 Information exibility and value added Information Economics and Policy 10431449 Return to REFERENCES Objective The primary objective of this report is to investigate the complex effects of information upon the firm A distinction is drawn between uncertainty and known variability and how these two factors in uence the quality of information and its impact on the firm Precision agriculture is mentioned brie y by the authors as an example Methods A spatial econometric approach is used to assess the value of information and its relation to revenue generation and to understand the mechanisms in uencing the change from uncertainty to know variability ie probability By understanding economic decisionmaking processes under uncertain circumstances and circumstances describable by probability distributions a clear definition of the economic effects of this shift from the quotunknownunimaginablequot to the quotprobabledeterministicquot can be formed To do this the authors construct a series of decision functions active in different environments These functions are associated with outcomes that are realized by choices acted upon by agents who are assumed to be profitmaximizing individuals Choice and action for agents are assumed exist as a complex between individual preference profiles and different environments differentiated by degrees of spatial dispersion Spatial dispersion simply assumes that certain choices associated with an outcome ie a technology have singular variances or probabilities of occurring or succeeding Spatial heterogeneity is learned by trial and error The value of moving towards known variability increases concomitantly with increases in spatial variability In short the authors suggest that farmers who use excessive amounts of inputs as a hedge against uncertainty will decrease mean input use upon adoption of sitespecific management practices since knowledge about spatial variability is known to some degree Crop any Technology precision agriculture risk adoption Region any 81 Hertz Chad A 1994 An economic evaluation of variable rate phosphorous and potassium fertilizer application in continuous corn MS Thesis Department of Agricultural Economics University of Illinois UrbanaChampaign Return to REFERENCES Objective To identify the conditions which affect variable and uniform rate fertilizer application profitability in terms of field conditions fertilizer recommendation guidelines agronomic assumptions and sampling densities Economic returns from variable and uniform rate applications are quantified under different levels of soil fertility The impact of variable rate applications is contrasted with alliterative recommendations of guiding uniform fertilization rates to determine how best to estimate which application method is economically feasible given certain field conditions Methods Expected marginal revenues from variable rate fertilizer application are compared to uniform rate application Example fields were generated to evaluate the model Data included field situations categorized as having low medium and high initial fertility conditions in areas across the field Fertility zones density varied throughout the field as low medium or high levels of variance Agronomic and economic rule based fertilization recommendations were compared to a conventional uniform application strategy An extension manual was used to estimate fertilizer application recommendations for the uniform and agronomic rule based recommendations Different soil sampling intensities were compared as well The final simulated model was tested using data from three farms ResultsConclusion Returns from variable rate application were superior to uniform rate applications However mapping costs soil sampling costs and variable application costs were not included in the partial budget analysis As spatial variability of fertility increases returns from variable rate treatments increased Crop corn Technology VRTP K Region Illinois Hertz Chad A and John D Hibbard 1993 A preliminary assessment of the economics of variable rate technology for applying r39 an r 39 in corn r J quot Farm Economics 9314 Department of Agricultural Economics University of Illinois Champaign Urbana Return to REFERENCES Objective To examine the total costs and capabilities of variable rate technology for phosphorous and potassium fertilizers Methods The authors use personal experience and results from other VRT research to describe the current state of the technology what considerations a producers has to keep in mind when deciding whether to adopt one or more of the components and what the costs and benefits associated with VRT are Actual data from original research provide a 82 foundation for a simulated comparison between conventional uniform and variable rate fertilizer application strategies for P and K Soil tests were conducted on a 40acre field using 16 x l6ft grids yielding 253 soil samples During the simulation three grid sampling sizes were compared with a commercial grid size of 25 acres The other sampling sizes were 10 and 0625acre grids Fertilizer rate recommendations were based on yield goals soil fertility results and the reference map and an extension publication explaining potential yieldP K soil fertility relations Rates for uniform fertilizer applications were determined as a fieldwide average of soil test values and additional aforementioned information sources For variable rate treatments applied rates were based on soil test values associated with a particular grid A partial budget including a longterm net present value framework is included in the analysis ResultsConclusion Although yields were higher for the lOacre and 0625acre grid sizes net retumsacre were highest for the uniform application strategy 9230 The longterm net present value over a 24year period was also highest for the conventional treatment 95984acre as opposed to the best VRT treatment a lOacre grid sampling size 95635acre The smaller the grid sampling size the more expensive soil tests and analyses were The authors conclude cautioning that these results could be misleading and that they need to be carefully interpreted First these results are generated from data representing one field Fieldtofreld variation undoubtedly exists and initial condition of a field will in uence the results of any sensitivity analysis Secondly the degree of spatial variability affects the outcome of partial budget analyses Optimal ratios of low and highyielding soils may exist Variable rate practices may be more feasible on land that has fertility mixes ranging from 20 to 80 lowfertility soils Third the present state of farm implements has not caught up with the precision of the tools available to determine field spatial variability Computer software and hardware have outpaced variable rate applicator technology to date economically and technologically Fourth model outcomes are dependent upon response functions Response functions too are variable from field to field region to region and year to year Crop corn Technology VRT Region Illinois Hollands KR 1996 Relationship between nitrogen and topography Precision agriculture proceedings of the 3r international conference June 2326 Minneapolis MN p3l2 ASACSSNSSSA Return to REFERENCES Objective To determine how well N levels corresponded with topological variations and to develop a map to be used during N application based on these findings Methods Soil sampling was conducted in tandem with elevation determinations This information was overlaid yielding a map that included information about the spread of field nutrients and the topography of the field Correlation between N levels and field 83 high and low points were attempted Without GPS soil sampling cost 12acre With GPS soil sampling was 19 acre but these results were more accurate ResultsConclusions Results of this study are graphically presented Six maps indicate results of soil testing coupled with GPS topography maps and N spread overlaid on top of elevation points The author states that although the methods used accurately determined the spread of N in relation to field elevations the technique alone is probably not cost effective However a schedule not detailed how maps generated using this technology might be useful over a three to four year period is presented The author concludes that the monetary costs of developing topological maps and software to read them into spreaders would outweigh the costs of repeated grid soil sampling Unfortunately no data was available to support this conclusion Although the author included the costs of soil sampling with and without GPS other costs such as the use of laser equipment used to take elevation readings fertilizer costs costs of delineating grids and consulting fees were not included A budget would have been useful In it estimated yields and projected returns could have been presented Crop sugar beets Technology VRTN Nitrogen map making GPS Region Minnesota Hombaker Robert H Roderick M Rejesus and Gary D Schnitkey 2000 Development and validation of a variable rate nitrogen program in Central Illinois Proceedings of the 5 International Conference on Precision Agriculture and Other Resource Management July 1619 2000 Radisson Hotel South Bloomington Minnesota USA Return to REFERENCES Objective The three main objectives of the report are l to devise a method for implementing VRTN programs based on historic and soil potential yields 2 to develop a validation protocol to determine whether optimal N rates are appropriate and 3 to conduct a feasibility study examining the economic implications of optimal N application strategies as determined by the validation procedure Methods The authors modify an equation furnished by the 1999 Illinois Agronomy Handbook that determines variable N application rates based on soil fertility and yield goal The modification incorporates a riskaverse variable sitespecific spatial components yield soil type the number of unique sites as xy coordinates time a five year production cycle is assumed and climactic variables A quotvalidation procedurequot was inserted into the model where 60 100 X 100 ft blocks are randomly selected Onethird of the plots receives 30 less N than the recommended rate another third receives 30 more N than the recommended rate and the remaining third receives the recommended N rate Results were kriged in 20 X 20 intervals Variables of interest were N rate yield and soil information 84 ResultsConclusion The experiment yielded mixed and unexpected results The authors conclude that the results do not contribute to the improvement of the application rule since the 30low and 30high N application rates produced signi cantly more corn than plots that received standard application rates The authors support the currently accepted notion that different soil types may require different N rates Crop corn Technology VRTN Region Illinois Hoskinson Reed L and J Richard Hess 1999 Using the decision support system for agriculture DSS4AG for wheat fertilization Precision agriculture proceedings of the 4th international conference July l922 p 17971806 ASNCSSNSSSA Return to REFERENCES Objective The authors discuss three different knowledge systems that in uence agricultural decisions the farmerbased system the scientific system and the cognitive information knowledge system or new technologies such as GPS or computer modeling applications The authors attempt to integrate these knowledge domains into a comprehensive system The possibility of applying computer learning algorithms arti cial intelligence AI is entertained since voluminous amounts of data are currently available Methods An expert system DSS4Ag was programmed to generate an algorithm for determining appropriate variable rates of multiple fertilizers on a l35acre field Soil nutrient and yield maps market prices were model inputs The field was divided into control and experimental plots 12 blocks total where DSS4Ag and control conventional fertilizer rates were applied Each block was 11 acres Yield monitors measured harvested wheat for each block ResultsConclusion Fertilization recommendations produced by the expert system recommendations generated savings of 1372 acre 391 compared to uniform application control rates Treatment blocks yielded less biomass The authors suggest that this is advantageous since less time is required to decompose the compost materials The economic forecast data indicated that wheat market prices were 335 acre 391 The sales loss using the expert system was 838 acre 391 but with returns from fertilizer saving a net benefit of 534 acre 391 was achieved The expert system in question could be compared with other methods used to extrapolate variable fertilizer application rates Additionally the model only focused on two variables Other multivariate dynamic optimization models might produce more a more accurate representation of spatial heterogeneity Crop potato wheat Technology modeling VRT Region Idaho 85 Isik Murat Madhu Khanna and Alex WinterNelson 1999 Investment in sitespecific crop management under uncertainty Paper presented at the Annual Meeting of American Agricultural Economics Association August 811 1999 Nashville Tennessee Return to REFERENCES Objective To examine the importance of sinking fund costs uncertainty in returns and elasticity in investment timing on producers decision to adopt variable rate technologies The decisionmaking process is framed in the context of uncertainty and irreversibility and the assumption that eld spatial variability affects crop yield Methods A behavioral model is developed followed by an analysis and summary of findings It is assumed that the producer is a profitmaximizing individual operating a field of a given size where soil fertility is spatially varied A crop response function was used to simulate yield in relation to soil fertility The farmer has a choice to manage variability using conventional uniform fertilizer application methods or variable rate technology Three fertilizer inputs are used in the model N P and K A 500acre field was assumed The field was divided into 25acre grids Soil fertility values were categorized as having low or high potential yields Two adoption scenarios were considered the producer purchases all the necessary technology or the producer custom hires services In both scenarios the producer was assumed to have a yield monitor equipped with GPS mapping software total 7855 to practice grid soil sampling 640grid In the first scenario the producer purchased a variable rate applicatorcontroller for 12345 The custom application service costs the producer 5acre annually The annualized fixed cost for the customhiring producer was 5227 while the cost for the producerowner was 5665 Equipment life span was assumed to be 5 years with a discount rate of 5 Service costs were assumed to decrease by 3 per annum Nitrogen potassium and phosphorous were assumed to cost 020 013 and 024lb respectively ResultsConclusion For all soil fertility zones considered in the simulation sitespecific management generated positive returns caused by yield increases Returns from low fertility zones ranged from 320 to 1070acre Highfertility zones generated positive returns ranging from 580 to 2370acre Fertilizer cost savings was also realized On lowfertility areas savings decreased from 310 to 130acre Fertility costs on high quality zones decreased 250acre The authors found that as soil fertility increased fertilizer costs increased since the marginal productivity of fertilizer application is increased The addition of extra fertilizer to highfertility zones increased the yield and was at least equal to the application costs When net present value analysis of site specific management strategies was considered adoption was not profitable on low quality soils and uniform soil distributions Investment is stimulated when soil fertility variability increased There were no differences between producerowner and producer custom hire scenarios NPV and the decision whether to adopt sitespecific management Immediate investment only makes sense when rent discount rate differentials are greater than the fixed costs of investment Higher soil fertility values and greater variations in 86 soil quality encourage adoption under uncertainty and depreciating asset scenarios RETURN TO INTRODUCTION Crop corn Technology VRT simulation Region Midwest Issaka Mahaman 1993 An evaluation of soil chemical properties variation in northern and southern Indiana PhD Thesis Department of Agronomy Purdue University West Lafayette IN Return to REFERENCES Objective To determine the economic feasibility of two variable rate fertilizer application technologies the soil potential approach and the nutrient approach The soil potential approach determines fertilization rates based on soil survey map units It is assumed that different soil types have different yield potentials and that by knowing the fertility of each soil type appropriate fertilizer rates can be determined The second approach is incorporates grid sampling in soil testing procedures A map is created and fertilizer is applied according to the soil test results and estimated yield potential of each cell Cells are assumed to be 2 to 3acre plots Methods Three management strategies were examined Fertilizing by soil types whole field fertilizing by fertility zones based on kriging results and fertilizing according to cell values linked to grids Grid cells were 900 m2 Data was obtained from a research farm and a private farm where field N and P values were highly variable Soil tests were conducted at both sites At the both sites soiltest results suggested three fertility zones Four management zones were delineated based fertility variation Recommended fertilizer rates as determined by the university extension service were adjusted according to soil test results Three treatments were examined whole field application applications based on grid sampling and management units determined by kriging Each grid cells was fertilized to its optimum amount Whole field application rates were based on soil sample averages A partial budget was employed to evaluate the profitability of the three management strategies ResultsConclusion Fertilizer use was reduced by kriging Fertilizer use was lowest in grid sampling units Yield for whole field management treatments was less 2894 bu than gridmanaged treatments 2963 bu Treatments using kriged maps were intermediate A11 variable rate treatments resulted in net return losses The author assumes this was due to significant underfertilization of some management units The author emphasizes that these results are based on only one years39 worth of data and surmises that if looked at over a fouryear period cost analysis changes Fertilizer use efficiency substantially increases using sitespecific management strategies In 1993 the high costs of testing were major constraints and decreased the likelihood of realizing increased net returns Return to Table 9 Crop corn 87 Technology VRT grid sampling Region Indiana Kasowski Mike and Dave Genereux 1994 Farming by the foot in the Red River valley Agri Finance December p 20 Return to REFERENCES Objective To illustrate the advantages of soil testing using grid sampling methods in conjunction with variable rate fertilizer application The authors are eld technicians for a consulting rm that provides fertilizer recommendations to sugar beet farmers in Minnesota Methods Testimonial based on personal experience is provided by the authors Their advice to sugar beet farmers is that there is much to learn in terms of field variability vertically not only horizontally The authors provide rationale why it is equally important to test at 4ft below field surface as it is to test at the commonly prescribed 2ft depth ResultsConclusion Fertilizer Recommendations based on test results from 4ft below the field surfaces provided information that boosted profits and product quality The authors revealed cases where profits have increased between 25 and 140acre for some farmers when deeper soil samples were included in testing protocol Some sample sites revealed ample amounts of available N If recommendations had been based on samples taken at depth of 2ft these zones would have been overfertilized Revenue increases were tied to larger sugar beet yields savings in fertilizer costs and a higherquality product According to the technicians an external benefit included less N being released into the environment Return to Table 9 Crop sugar beets Technology grid sampling VRT Region Minnesota Kessler Mark C J LowenbergDeBoer 1998 Regression analysis of yield monitor data and its use in finetuning crop decisions Precision agriculture proceedings of the 43911 international conference July 1922 p 821828 ASNCSSNSSSA Return to REFERENCES Objective The report investigates which how statistics can be used to assess sitespecific responses to inputs and how these relationships might augment revenue Methods In this exploratory study regression analysis was used to determine how SSM management in uenced crop yield Three years worth of production data 19941996 from an operating farm were used Yield monitors quantified harvests Whole field soil tests were carried out before 1994 on 05 acre grids Variables used in the historical regression model were yield crop corn or wheat tillage soil test year soil pH applied 88 N P and K and planting date The same variables used in the above model were included in the gridbased model including production year soil texture sand silt or clay cationexchange capacity and percent organic material An economic analysis included corn price as well as signi cant variables signi cant at the 005 level from the above models These results were used to optimize input prices output and farm operation costs Using coefficients generated from the first two models three scenarios were simulated a whole rate soil test an uniform application using grid information to calculate optimum levels for each grid varying the fertilizer rate accordingly and using grid information to determine whole field fertilizer rates ResultsConclusion In the historical model the most controllable variable seemed to be the planting date There were no other variables under the control of management that were significant The gridbased model explained some of the variation in the data However spatial correlation was not explained Using assumed corn and fertilizer prices whole field soil testing and uniform fertilizer application was the most economically feasible practice for this farm The authors conclude that historical data does not provide much direction for management and that grid based soil testing can generate useful coefficients for controlling certain management variable such as fertilizer application rates Additionally the results presented are presumed to be affected by spatial correlation Lastly recommendations based on collected and analyzed information will be affected by market prices Return to Table 9 Crop corn Technology VRT modeling Region Indiana Khanna Madhu 1999 Sequential adoption of sitespecific technologies and its implications for nitrogen productivity a double selectivity model Selected paper for the annual meeting of the American Agricultural Economics Association Nashville TN Aug 811 1999 Return to REFERENCES Objective To develop a model that explains the factors related to the adoption of site specific crop management technologies and the pattern and implications of adoption for nitrogen management That an individual producer s decision to adopt any new agricultural technology most likely occurs sequentially is a central assumption of the model Methods One thousand grain farmers in Indiana Iowa Illinois and Wisconsin were randomly selected Six hundred and fifty farmers responded to a survey which asked respondents why they chose one soil test over another and whether or not this information was used for VRT This study used eight main variables scale economies human capital land ownership soil quality propensity to innovate adoption costs and location A double selectivity model is used to differentiate farmers that do not adopt either soil testing technologies or VRT soil testing only or soil testing and VRT 89 ResultsConclusion The author found that one of the most in uential factors of VRT adoption was location Farmers in Indiana Wisconsin and Iowa were more likely to adopt soil testing technologies than farmers in Illinois Proximity to farm and fertilizer dealerships in uenced the adoption frequency of VRT Acres farmed had no impact on the decision whether or not to adopt soiltesting technology Producers fa1ming higher quality soil were more likely to adopt VRT than those farming relatively poorer soil However gains in nitrogen productivity were greater on poorer soils following adoption of soil testing and VRT Adoption of soil testing only did not affect nitrogen productivity Farm owners were less likely to adopt VRT than those leasing land Double selectivity model results suggest that corn productivity of fa1mers not adopting soil testing or VRT decreased as the acreage cropped increased Farmers using manure produced more grain per unit nitrogen than farmers who did not College educated non adopters farming higher quality soils attained higher nitrogen productivity than other farmers The author concludes that technically proficient educated producers capable of spreading the costs associate with learning and information gathering over a large number of acres were more likely to adopt soil testing and VRT The model would be more realistic if yield data from crops ie corn was used in the analysis and if the author incorporated more than one growing season in the analysis A budget describing the costs technological bundle of VRT would reinforce the argument provided by the author that producers adopt technology sequentially Instead the report subsumes the components of VRT under the general heading of soil testing and VRT Crop cash grain crops Technology VRTN modeling Region Illinois Iowa Indiana Wisconsin Khanna Madhu Onesime Faustin Epouche and Robert Hombaker 1999 Sitespecific crop management adoption patterns and incentives Review of Agricultural Economics 212 455472 Return to REFERENCES Objective To investigate the extent to which producers are adopting precision agriculture technologies identify an adoption pattern based on the components chosen by farmers and possible trends associated with these choices Sitespecific technologies have been categorized into three general domains 1 information collection and management technologies for discerning field variability 2 technologies linking this information to the field such as yield maps combined with GPS or remote sensing 3 application technologies allowing farmers to apply information such as variable rate applicators Methods One thousand mail surveys were sent to cash grain farmers in Iowa Illinois Indiana and Wisconsin Respondents were randomly chosen They were asked whether they used computers soil testing grid sampling with GPS application technologies yield monitors and variable rate application of pesticide herbicides or fertilizers 90 ResultsConclusion Adoption of simpler diagnostic equipment such as computers and nongrid soil samples was more frequent than adoption of highly engineered technologies such as yield monitors GPS and gridbased sampling Individuals who had adopted use of the latter technologies owned or manage larger operations The authors suggest that producers endowed with human capital technical skills and the resourcefulness required for collecting and analyzing highly detailed data were presumed to have lower costs of incorporating these technologies into their decisionmaking process Adopters of advanced technologies were already using computers Adopters tended to be less than 50years old had a college education managed larger farms and had historically higher yields than nonadopters The authors identi ed three adoption patterns path dependency leapfrog and threshold adoption patterns Survey results indicated that the first pattern represented the adoption behavior of most producers interviewed Farmers had already incorporated computer technologies into their farming operations A logical nextstep would be a technology that would interface with this component Adoption patterns for some farmers were of the second type Producers would adopt advanced technology packages without having tested less compleX precision agriculture technologies According to the author one factor impeding adoption rates is the lack of information about the benefits of precision agriculture Another reason is that farmers are satisfied with their current production levels their machinery and their production routines Payback from precision agriculture technologies is also dubious The authors assume that as farm implements senesce producers will be more willing to try technologies associated with precision agriculture Crop na Technology precision agriculture general Region Midwest Kitchen NR DF Hughes KA Sudduth and 8 Birrell 1994 Comparison of variable rate to single rate nitrogen fertilizer application corn production and residual soil N03N Sitespecific management for agricultural systems proceedings from the 2quotd international conference March 2730 Minneapolis MN p 427439 ASNCSSNSSSA Return to REFERENCES Objective The authors address the following questions 1 Can N03 leaching be circumvented while increasing sustainable production of corn using VRT 2 how useful are yield maps from prior production years be for predicting next year s yield potential and corresponding fertilizer maps Methods Four study sites over two growing seasons were subjected to conventional and VRT N application protocols N application rates during the experiment were determined using yield maps generated from previous seasons yield results A combine equipped with sensors measured yield N uptake by plants and unrecovered N were detected using soil samples Grain production unrecovered N and postharvest soil nitrates were measured A crude partial budget was used to evaluate the profitability of VRTN 91 ResultsConclusion Yield was not help nor hindered by VR The authors found that N was more limiting a factor as VR applications reduced yield when all experimental units were compared across the first three study sites claypan soils Increased N limitation was accounted for by high soil moisture conditions during seed ll When application strategies were compared across experimental units and treatment regimes VR N produced better than expected yields In study site 4 alluvial soils there were no differences between N application strategies In the first three studies unrecovered N decreased in the least productive soils when VR was used Yield mapping improved the ability to apply N fertilizer accurately in contrast to basing application decision on the best years or best area The authors provide a budget comparing conventional and VRTN applications In short there was not much difference between expected returns of conventional and VR applications The authors did not take into consideration the costs of conducting VR Inclusion of this cost would probably render conventional application methods more cost effective than VR in this study Crop corn Technology VRTN Region Missouri Letey J H Vaux and E Feinerman 1984 Optimum crop water application as affected by uniformity of water infiltration Agronomy Journal 76 MayJune 435441 Return to REFERENCES Objective To report a methodology for determining how variable water infiltration rates on corn and cotton crops affects yield optimum water application and net returns Methods A response function model is developed to determine the amount of irrigated water absorbed by crops or lost to evapotransporation or runoff Data was selected from other research results as well as response functions for cotton and corn Six arbitrary water infiltration rates were examined Water infiltration rates correspond to amounts of water provided by irrigation ResultsConclusion As infiltration rates variability increased corn yield decreased Applying prescribed amounts of water in these zones offset decreases in yield caused by infiltration nonuniformity However with cotton additional water did not offset low yields when infiltration was nonuniform When water prices were low and water infiltration rates were assumed to be heterogeneous the optimal average amount of water increases More water can be irrigated over a nonuniform field when water prices are low The converse is true as well It can be inferred that by knowing fieldwater infiltration coefficients hydrological maps could be developed to deliver prescribed amounts of water to specific infiltration management zones Return to INTRODUCTION Crop corn cotton Technology VRTirrigation 92 Region California Long DS GR Carlson and GA Nielsen 1996 Cost analysis of variable rate application of nitrogen and phosphorus for wheat production in northern Montana Precision agriculture proceedings of the 3rd international conference June 2326 Minneapolis MN p10191032 ASNCSSNSSSA Return to REFERENCES Objective To establish whether VRT is more pro table than conventional uniform N application strategies using yield goals and grid soil sampling of smaller field areas exhibiting spatial variations in productivity Methods Three trials compared wheat production over three years The first trial was conducted on a 41ha field in a summer fallow rotation The second site was a 21ha field in a chemical fallow rotation The third trial involved P fertilization on three 15ha fields Soil N was determined to establish treatment N rates The experimental model was a randomized block design with three replications and five to six treatments N rates were different each year treatments except for the increments 0 to 112 increasing by 23 kgtreatment differentiating each treatment P treatments were 0 12 24 36 48 and 60 kg Pha Fields were divided into strips and fertilizers applied accordingly Experimental rates were determined using soil samples and remote sensing data that portioned fields into managementfertility zones The number of samples conducted over the field and the grid sample sizes was not made explicit However soil test were conducted at two levels 60 and 120cm Wheat was harvested using a yield monitor Wheat prices yielded from both VRT and uniform rate treatments were determined using the average grain protein produced in each strip Net returns for each treatment were calculated by subtracting fertilizer costs soiltesting costs and fertilizer application costs from gross returns Nitrogen was assumed to be 0407kg Soil sampling costs for a 41ha field were assumed to be 5500 per sample for uniform rate recommendations and 4800sample for VRTN recommendations Uniform rate application charges were 554ha VRTN application charges were 1235ha ResultsConclusions First the authors compare the returns from VRTN and uniform rate strategies in terms of fertilizer recommendations base on two different soil test depths Profitwise returns from VRTN were superior than those from uniform rate technology at 43300ha at a cost of 4300ha and 37200ha at a cost of 1700ha respectively base on soil tests from the top 60cm Results were different when soil test data from the top 120cm was used Uniform rate treatments 32700ha at a cost of 100ha were less cost effective than VRTN 34400ha at a cost of 2500ha The authors attribute this to the skewed results generated by the soil tests A few regions in the field had very high nitrogen readings Using averages other portions of the field with lower N rates would not receive sufficient amount of N fertilizer under a uniform application strategy Results of profitability analyses comparing VRTN and uniform rates were similar when data from the following growing season were analyzed Returns from VRTN were greater than they were for uniform rate treatments However results were attributed to nitrogen carryover effects rather than skewed results More N could 93 be precisely applied to region known to be highyielding using VRTN Returns were not compared for P trials Using market quotes for protein content proved useful during profitability analyses This method links farm activities to wider offfarm contexts and demonstrate the connectivity of onfa1m management decisions and less controllable external processes such as markets and costs of implementing new technologies Crop wheat Technology VRTN Region Montana Lilleboe D 1996 Will it pay The Sugar beet Grower February p 1820 Return to REFERENCES Objective To describe the use of grid soil sampling and variable rate fertilizer application in the sugar beet industry in South Dakota and Minnesota Specific attention is paid to the profitability of the practices combined and the total acreage of sugar beet farms that have adopted these technologies Methods The author uses case studies farmer testimonials and regional production data to describe the grid samplingvariable rate application process and the net returns resulting from these precision agriculture technologies ResultsConclusion Responses from a consultant working for a sugar beet processing company point out that variable rate fertilizer application will only be profitable on some sugar beet fields If gridsampling results indicate that field fertility is not highly variable then VRT should not be considered To little nitrogen results in poor yields while too much results in lowquality sugar beets Grid sampling can indicate where exactly low and highfertility zones are located in fields and at what ratio Where soil nitrogen content was less than 30 lbsacre returns from gridsamplingVRT paid off only 31 of the time The consultant said that 70 of the 897 fields sampled had enough soil fertility variability for them to be considered candidates for variable rate fertilizer spreading In this consultants work zone 80 of his recommendations were successful in terms of profitability Other zones in MinnDak fared less well at 50 of the recommendations making returns on gridsamplingVRT investments Variations in weather patterns were held responsible for these results The author indicates that the general attitude held by companies providing gridsamplingVRT services is that the more information a producers can have about their field the easier it is to pinpoint problem area When these areas are found then more or less dollars and cents can be spent there Crop sugar beets Technology grid sampling VRT Region South Dakota Minnesota 94 Linsley CM and FC Bauer 1929 Test your soil for acidity Circular 346 University of Illinois Agriculture Experiment Station Return to REFERENCES Objective An early extension circulation promotes systematic testing of soil pH and using the results to make pHdistribution maps representing management zones Methods A stepbystep methodology how to test soil pH then use the information to create maps is given A spacing of 8 rods 132 ft between sampling points is recommended A simple net return minus costs was used to estimate savings gained using this information strategy ResultsConclusion A case study is offered by the authors to emphasize the importance of testing soil before purchasing lime In 1929 not testing soil pH cost farmers quotmany thousands of dollarsquot each year in both lime and clover seed Farmers would sow at least 40acres of red or sweet clover on land that was too acidic Clover will not grow on acidic soils Unaware of the soil pH of a eld a farmer would plant clover on acidic fields and quotlose 50 to 100 dollarsquot worth of seed for every 40acres seeded The onus of low clover production was commonly attributed to poor weather The authors argue that if this amount were invested in agricultural lime lowpH fields would be ameliorated They warn however that the spatial variability of field pH has to be determined before purchasing lime In another testimonial a farmer had ordered 120 tons of limestone for a 40acre field Before the shipment arrived he had conducted a soil test and mapped the results The results indicated that he needed to apply only 60 tons of lime and would have saved 120 The authors end the circular quotDon39t Guess Testquot Crop clover Technology VRT Region Illinois LowenbergDeBoer J R Nielsen and S Hawkins 1994 Management of intrafield variability in largescale agriculture a farming systems perspective SystemsOriented Research in Agriculture and Rural development International Symposium Montpellier Francs November 2125 1994 p 551555 Return to REFERENCES Objective To determine the best methods to use informationgenerating tools such as GPS onboard computers variable fertilizer applicators and onthego yield monitors in variable rate fertilization programs The economic importance of understanding intrafield variability is emphasized along with VRT efficacy based on decisions made using soil fertility maps Methods Fields on four farms were divided into three equalsized plots Three fertilization treatments were tested whole field soil type and grid management Whole field fertilizer rates were based on the average nutrient levels P and K of two soil samples per field Fertilizer rates for the second treatment were based on soil test results 95 for the specific soil type A uniform fertilizer rate was applied to the soil type based on recommendations according to the test results The third treatment divided the eld in a series of grids Soil samples were taken from 14ha cells within each grid A recommended fertilizer rate is made for each cell Fertilizer is applied uniformly in each cell A GPSquipped yield monitor was used to quantify production and log yield spatial distribution The relative costs of three soil mapping techniques were compared These techniques were gridbased maps kriged maps based on linear semivariograms and kriged maps using a Gaussian model ResultsConclusion VRT fertilizer recommendations are sensitive to the mapping technique used to determine soil fertility zones However the researchers found that kriged maps revealed soil fertility patterns that were incongruent to the farmers experience with the field Furthermore kriged maps did not necessarily correspond with soil test results Gridbased maps cost 2483ha while the kriged maps cost 1843 and 1545ha respectively In this report soil test cost between 6 and 18sample depending on the type of test When spread out over a three to four year period as dealerships providing these services will do grid soil tests fall to 250ha annually Mapping fees under this system are 7ha Since variable rate spreaders can cost on the order of 250000 farmers are more likely to hire VRA services Conventional custom spreading costs 10ha while VRT spreading costs are higher at 13 to 18ha The authors conclude that framers perceive VRA as a method to increase efficiency on a given field rather than a way to expand farm operations Agrochemical dealerships see VRA as a way to assuage criticism from the environmental sector to market a new product and as a new profitgenerating mechanism The producer according to the authors will become either coordinators of this new technology or at worst laborers implementing outside eXperts management plans RETURN TO INTRODUCTION Crop corn Technology VRT Region Indiana LowenbergDeboer Jess 1995 Economics of precision farming payoff in the future Paper presented at the Precisions Decisions Conference Champaign Illinois November 2728 1995 Return to REFERENCES Objective To provide a general review of the economics of PA identify possible future benefits and define an adoption strategy for long term competitive advantage Methods The author defines terms such as cost benefits shortterm profitability and adoption strategies in relation to PA 96 ResultsConclusion Table 21 Pro tability conclusions from 11 Precision Framing Studies Study Crop Inputs Managed Treatment of PA Profitability Sampling amp VRT Cost 39 Carr et a1 Wheat barley N P K Not included Mixed Fiez et a1 Wheat N Not included Yes potentially Ham mond Potato P K Variable amp fixed lnconclusive costs on y LowenbergDeBoer Corn P K Variable amp fixed No but might for et a1 custom rates lowsoil test fields Wibawa et a1 Wheat N P Variable amp fixed No but overest wlyr amort annual fixed costs Wollenhaupt and Corn P K Variable amp fixed Mixed deps on Buchholz w4yr amort yield gain Wollenhaupt and Corn P K Variable amp fixed Mixed deps on Wolkowski w4yr amort sampling density and amort perio Simulated Yields Beuerlein amp Schmidt Corn soy P K Variable amp sample No but more no equip efficient fertilizer Hayes et a1 Corn N Not included Higher revenue has potential to cover costs Hertz and Hibbard Corn P K Variable amp fixed No but close to custom rates uniform in proftiabiulity Mahaman Corn P K Variable amp fixed No if lyr sample custom rates amort yes if 4yr sample amort Source LowenbergDeBoer J and SM Swinton 1997 Precision agriculture economic feasibility studies have oftentimes omitted the costs of developing human capital in budgets Human capital development would include training individuals how to use interpret and maintain PArelated equipment including computer training and data interpretation Similarly the time spent while learning these new technologies and the costs associated with lost time have not been included in budget analyses Human development costs also include any workshops or seminars that address training issues Useful life of equipment should be incorporated into pro tability analysis If equipment has to be updated or replaced after four years these costs could substantially affect partial budget analyses Generally returns from PA technologies are higher and more consistent when used with high value crops Returns from PA to production of bulk commodities are low However these gures might be confounded by management strategies The author concludes that agriculture has become a data 97 driven knowledgebased enterprise Some producers will opt for custom PA services in efforts to build personal data bases re ecting the spatial variability of their farms Other producers first venture into PA might include purchase of a yield monitor as has been the case with many grain fa1mers on the heartland Yield monitors set the stage for adoption of GPS guidance systems yield mapping and management decisions based on the combination of these technologies Over time some PA technologies will become standard practices in North America Other technologies or combinations of technology will become obsolete Crop any Technology PA summary Region North America LowenbergDeBoer J 1995 Management of precision agricultural data Selected paper presented at the Annual Meeting of the American Agricultural Economics Association Indianapolis August 1995 Return to REFERENCES Objective To detail the problems of managing massive amounts of data generated by precision agriculture technologies The analysis entertains information ownership information use and costs of managing information Methods Using personal experience and recent literature the author reviews the current state of information collection management and associated costs for precision agriculture technologies ResultsConclusion The author concludes that an effective method for understanding the costs associated with managing precision agriculture data is focusing on the economics of scale associated with information costs management and collection That farming enterprises capable of affording the composite of technologies needed to effectively implement most precision agriculture technologies and that concomitantly large amounts of information will be needed to provide these technologies effective leads to the formation of professional private or academic organizations specialized in this task RETURN TO INTRODUCTION Crop na Technology Precision agriculture information management Region all LowenbergDeboer Jess Steve Hawkins and Robert Nielson 1994 Economics of precision farming Extension Manual Department of Agricultural Economics Purdue University West Lafayette IN 47907 Return to REFERENCES Objective To summarize research results investigating the management of precision farming technology 98 Methods In 1993 variable rate application trials using P and K were conducted on four elds eight producers total each approximately 50acres Soil variability mapping techniques and the efficacy of onthe go yield monitor data was investigated ResultsConclusion Soil test results indicated that well managed elds display large differences in soil fertility even after being managed on a wholefield basis Variation stems from varying soil types as well as past management decisions Magnitude of variability was different for each farm meaning variable results from one farm may not have indicated P or K applications whereas the range of variability on another farm warranted sitespecific application of these elements Three figures display 3 dimnensional grid maps of P spatial variability Each map was generated using different inferential techniques grid mapping based on 3acre grids and krigging using Gaussian or linear models The grid map and custom P application cost 60 more than kriged maps using the Gaussian model The kriged map using the linear model including P application cost 80 that of the grid map Gird maps generate a wider range of extreme high and low fertility values than kriged maps Yield monitor results proved to be within 2 of weigh wagon yield measurements Where farms are wellmanaged the authors conclude that returns from PA will be realized not in increased yields but in decreased input use The authors warn that producers considering adopting PA technologies have to keep in mind human capital costs computer software and hardware costs and the costs associated with learning and training 99 Table 22 An example of precision farming costs for a 3 acre grid and a 4 year soil sampling cycle Item Unit Quantity Price Amount Soil sampling sample l3l4 900 075 Map making acre 1 250 250 Record keeping acre l 100 100 Extra application acre 1 300 300 cost Total cost a 725 Return to Table Listing Crop corn Technology mapping soil testing yield monitoring Region Indiana LowenbergDeBoer Jess 1996 Precision farming and the new information technology implications for farm management policy and research discussion American Journal of Agricultural Economics 78 12811284 Return to REFERENCES Objective To focus on the historical development the state of economic research in the precision agriculture eld Methods The author reviews and critiques three reports concerning precision agriculture Of import is the lack of attention paid to the historical development of precision agriculture the value of economic analysis and its role in determining the feasibility of precision agriculture and the needs created by the inception of precision agriculture such as decision support systems and data analysis and management ResultsConclusion The development of precision agriculture in the United States can be compared to the adoption of mechanized farm implements Like the incorporation of the tractor into farm operations an extensive history of informal and formal crop systems information where producers balance costs and bene ts of data collection analysis and implementation are the foundation of precision agriculture and in uence the rate and frequency of adoption on a farmbyfarm basis Additionally assuming widespread adoption of precision agriculture no one can predict the consequences that will follow With the complete adoption of motorized implements not only the structure of the farm changed but also farming as a lifestyle was transformed into a business These whole farm changes were not anticipated with the inception of motorized farm implements Economically there has been little research how precision agriculture technologies have affected farming operations at the wholefarm level or the agricultural sector as a whole Structural changes might include the breadth of control over more acreage precision agriculture product diversification and food safety The promotion of precision agriculture has created a need for human resources Experts understanding risk pro t potential structural impact and policy implications become essential as precision agriculture components are integrated into farming systems The author anticipates the 100 formation of interdisciplinary teams that will focus on data management and interpretation development of algorithms for determining crop yield responses and education and training These decision support system teams might include nationwide farm implement dealerships private consulting services and university departments RETURN TO INTRODUCTION Crop any Technology precision agriculture general Region United States LowenbergDeBoer J and M Boehlje 1996 Revolution evolution or deadend economic perspectives on precision agriculture Proceedings of the 3r international conference June 2326 Minneapolis MN p 923944 ASACSSNSSSA Return to REFERENCES Objective The objective of this report is to provide an economic perspective on precision agriculture Three main themes are presented First the profitable margin of precision agriculture at the farm level is discussed Then the authors discuss the economics of information collection and management Lastly how precision agriculture might further industrialize North American agriculture is discussed Methods The authors review studies that examine profitability of precision farming First they present a brief epistemology of knowledge production followed by the forms of knowledge that comprise useful information for precision agriculture Then farm level profitability studies and equations used to understand farm level profitability are given Data from a survey conducted by the authors is presented Respondents were farmers who had practiced precision agriculture in one form or another at one time They were asked where they had obtained information about precision agriculture and which sources were most valuable Partial budget methods are outlined followed by a critique of several partial budget studies ResultsConclusion The authors characterize information useful to the objectives of precision agriculture as timely accurate objective complete clear and convenient Reviewing partial budgets the authors suggest that results from previous studies were contingent upon the manner in which the costs of sampling and variable rate application were handled When the authors asked why some partial budget assessments of SSM were profitable they found that the costs associated with information collection and management were excluded Similarly the question was asked why some partial budget analyses found SSM unprofitable Simply the costs outweighed the benefits But information collection and management costs were not spread out over the entire production spectrum Instead they were only distributed over a few nutrients High soil fertility implies low costs for fertilizers hence benefits are not attributable to SSM from this perspective That fixed costs were not annualized and in ation of fixed costs due to small grid cells used for soil sampling are other reasons why SSM may have been classified as unprofitable in these partial budget studies For mixed results SSM 101 pro tability hinged upon attainable yield sampling density and the duration of the validity of soil maps Information collection and management costs should be distributed over many inputs not just fertilizer since information is a resource that can be combined with other knowledge bases or used alone to attack other farm functions besides fertilization activities According to the authors precision agriculture could potentially change the present structure of industrial agriculture by reducing production costs while increasing efficiency expanding control over previously uncontrollable variables diversifying products safer foods and environmental benefits RETURN TO INTRODUCTION Crop any Technology precision agriculture Region North America any LowenbergDeBoer J 1997 Taking a broader view of precision farming benefits Modern Agriculture 12 3233 AprilMay 1997 Return to REFERENCES Objective To examine the economics of in precision agriculture other than yield increases and input reduction These two fieldlevel factors are commonly used to gauge the economic feasibility of precision agriculture technologies A broader definition provides a more accurate and realistic assessment of the value of precision agriculture Methods The author uses personal experience to discuss potential benefits of precision agriculture other than increased yield and input reduction A brief list of economic terms is presented along with their definitions and how they relate to precision agriculture ResultsConclusion Other potential benefits of precision agriculture include diagnostic information efficient equipment use risk reduction monitoring and supervision product diversification food safety and environmental stewardship Diagnostic information includes yield maps soil maps or other maps representing cropfield spatial and temporal relations When diagnostic information is collected over time it can be used in whole field management strategies and longterm planning Efficient use of equipment is another potential benefit of precision agriculture With refined and detailed information about weather patterns or field conditions operators can better schedule fertilizer application dates and sequencing use of farm machinery GPS technologies enable operators to maneuver at night or during poor weather conditions Overlaps and skips are also reduced with GPS technology Risks can be reduced with adoption of precision agriculture technology At the field level sitespecific management practices can reduce intrafield variability which results in a decrease of variability in net returns across the entire field At the wholefarm level information generated by precision agriculture can be used to make informed decisions about crop rotation sequences marketing strategies and crop variety Information from GPS units can facilitate monitoring and supervision of falm employees and machine operators Activities such as spraying or planting can be logged then evaluated at a later time Monitoring crop growth during the growing season is a laborintensive endeavor GPS technology decreases the amount of time spent 102 scouting elds for problem areas Precision agriculture may aid producers in diversifying their products For example exploiting the natural topography of a eld could enhance wheat protein content Knowledge of this information could provide a producer more than onegrain grade at harvest Food safety can also be enhanced with precision agriculture technologies Field operation can be recorded so that if problems arise the exact origin of the problem can be located in the field correlated with a fertilization record and matched to a fertilizer map if necessary By limiting fertilizer input based on knowledge about soil fertility zones precision agriculture can also reduce the risk of groundwater contamination RETURN TO INTRODUCTION Crop any Technology precision agriculture general Region any LowenbergDeBoer J 1997 Bumpy road to adoption of precision agriculture Purdue Agricultural Economics Report November 1997 p l4 Return to REFERENCES Objective To identify patterns characteristic of technological change with the intent to provide producers and others involved in agribusiness a historical perspective that may be useful for making decisions about adopting precision agriculture technology Methods The historical development and fate of several agricultural innovations is reviewed Particular emphasis is placed on hybridization and farm implement mechanization ResultsConclusion If a graph were used to indicate the adoption of a particular technology an Sshaped curve would emerge At first there is only a slight rise from the inception of the technology and the number of users Combinations of factors contributing to this might include the region specificity of the product marketing problems cost a general unwillingness of the target group to change current practices or a combination of these Assuming the technology produces any economic benefit a group of early adopters or innovators will continue to use and perhaps modify said technology The curve r y rises as ies too implement and adopt the technological package after seeing the benefits gained by their neighbors The s curve plateaus after the spread of the technology has saturated the usergroup community Either some refuse to adopt the product or the returns diminish as higher revenues generated by the technology become stabilized The problem faced by precision agriculture is that it is not a complete unified package Precision agriculture is currently more of a concept than a product Whereas tractors and hybrid corn essentially arrived as one package deal precision agriculture is comprised of several kinds of technology including variable rate spreaders and applicators GPS and GIS services yield monitors soil fertility and conductivity maps data analysis and management and computer hardware and software The author concludes that the adoption pattern of precision agriculture will not follow the traditional sshaped curve for several reasons The technologies that make up precision agriculture are immature and are still in the research A n A 103 and development phase This stage lends itself to experimentation and tinkering by user groups Producers will pick and choose which components suit their operations and discard others that do not Secondly precision agriculture is by de nition information technology applied to agriculture There is currently no consistently reliable institution to handle the vast amounts of information assumed to be required that make precision agriculture work Lastly the agricultural sector has become a riskier business since the government has withdrawn from price stabilization programs Although nearly 13 of today s combines are outfitted with yield monitors these factors challenge rapid adoption of precision agriculture especially in the combelt region Crop any mainly corn Technology precision agriculture technology adoption Region any mainly Midwest LowenbergDeboer Jess 1997 Economics of precision farming implications for the Canadian prairies In Farming to the Future Precision Agriculture Conference Brandon Manitoba November 1997 Return to REFERENCES Objective To provide information pertaining to adoption strategies of PArelated technologies in Canadian prairielands The author reviews the current state of the economics of PA highlight key issues relating to the adoption of VRT discuss other possible uses of PArelated technology that may play promote profitability and review adoption patterns Methods The author offers personal experience and knowledge while describing how the costs and benefits associated with FA adoption are affected by short term profitability information equipment efficiency risk reduction and product differentiation ResultsConclusion PA agriculture feasibility studies focus on changes in crop input costs such as fertilizer and herbicide but have sometimes ignored investment costs especially costs associated with human capital training personal learning curves database management and other computer skills Furthermore not annualizing the useful lifetime of equipment into budget analyses ignores annual cost fees or equipment thus potentially underestimating PA profitability For example computers or software may be obsolete within five years Omitting equipment deprecation the annual use costs can be relatively high The author suggest that the benefits of PA have been difficult to measure or generalize since there is still debate amongst researchers as to which appropriate experimental designs are useful for validating yield monitor data and which models best re ect field variability are still under development The central factors governing VRT profitability and adoption are 1 whether an integrated system with sitespecific management multiple inputs exist or is available to a producer 2 the development of better crop response function models 3 PArelated equipment availability on a masslevel 4 accumulated experience of producers using a composite of PA technologies Diagnostic information generated by yield monitors remote sensing and grid soil sampling not only identifies spatial variability patterns in fields Diagnostic 104 information as records becomes a whole farm information system Pa technologies can improve equipment efficiency For example GPS guidance packages enable operators to work elds at night and information about soil fertility and weather patterns could be used schedule and sequence equipment use Crop risk can be reduced using PA technologies as well For example VRT P amp K applications combined with grid soil tests have been shown to reduce net return variability by 25 Lastly onthego yield monitors could potentially help differentiate crops into two or more quality grades The author concludes by describing the adoption patterns characterizing PA technology see LowenbergDeBoer J 1998 Crop na Technology PA general adoption Region Canada LowenbergDeBoer J and SM Swinton 1997 Economics of sitespecific management in agricultural crops In Sitespecific management for agricultural systems p 369396 ASNCSSNSSSN Madison WI Return to REFERENCES Objective The authors focus on the variables needed to verify sitespecific management SSM profitability In additional field level economic studies are reviewed to understand necessary conditions for SSM adoption in terms of risk profitability and environmental regulations Lastly the authors asked how SSM would impact US agriculture Methods The study provides a protocol for the economic analysis of SSM In addition it provides a review of the available literature on this topic The authors provide a vocabulary for understanding SSM in economic terms Techniques such as partial budgeting investment analysis calculations for gross margin and net revenue and methods to factor in environmental benefits are included along with a literature review of SSM material ResultsConclusion SSM can provide a quotspatial dimensionquot to crop management The large amounts of information needed to understand spatial dynamics can be facilitated using automated data gathering techniques However research on the economic feasibility of SSM has not included costs associated with learning training or information collection and management Other studies have neglected the use of actual field data in their estimations A owchart provides a systematic examination whether or not SSM will be profitable for a farm firm First partial budget re ecting cash ow change of a typical production season needs to be enumerated If SSM does not cover variable operating costs then the farm manager will most likely not adopt it If these costs are covered the next step in the decision making process is to conduct an investment analysis Added variable costs of SSM include for example precision spreading costs map making soil testing and training When additional variable costs of SSM are covered then an investment analysis estimating the capital costs of information collection and management and special equipment needed for SSM is made Some 105 investments can be annualized since they are useful for several years Examples include computer software and hardware eld sampling data input and analysis and data base development Adoption risks can be factored into the decision making process Yield variance from SSMmanaged elds can be compared with historical yields of the same or similar elds that have been managed under conventional practices ie uniform fertilizer application A risk dif cult to quantify is that of durable goods discontinuation of their production and cessation of support services This typical pattern observed with the introduction of new technologies characterizes SSM adoption as well Software or hardware may prove to be useless Lastly even if partial budgeting and investment analyses demonstrate that SSM may not be cost effective environmental bene ts are a form of direct nancial gain or contribute to wider social well being and can be factored into the decision making process SSM pro tability is sitespeci c SSM implementation should be determined on a farmbyfarm eldby eld basis Dif culties evaluating the economic bene ts of SSM include connecting changes in crop yield to SSM Longterm eld studies understood using time series auto and spatial correlation analysis are techniques capable of explaining the cause and effect mechanisms between crop yield and SSM These question remains how much detail is needed to manage elds using SSM technology 106 Table 23 Gross margin and net revenue calculation example for variable rate technology application of P and K plus yield monitoring Item Unit Quantity Unit Price Total Change in crop revenue corn yield Kgbu 11441 450 009 230 103500 change Soybean yield change Kgbu 1362 50 0195 530 26500 Change in variable cost SSM services Haacre 405100 1791 725 72500 Change in fertilizer cost Haacre 405100 793321 32100 Differential correction fee yr 1 600 8000 Added repair cost Haacre 405100 032013 1315 Added interest on variable costs at dollars 1139 500 5696 10 for 6 mos Change in total gross margin Haacre 1 104 Capital costs Yield monitor Haacre 405100 541 2 1 9 21926 GPS unit Haacre 405100 245099 9867 Training Haacre 405100 067027 26 81 Change in total net revenue Haacre 405100 240 84 Change in net revenue per ha391 acre39l ha391 acre39l 1 595 241 unit land Return to Table 9 Table Listing 0r INTRODUCTION Crop corn soybean any Technology VRT sitespeci c management Region any LowenbergDeBoer J 1998 Economics of variable rate planting by yield potential zones Purdue Agricultural Economics Report May 1998 p 67 Return to REFERENCES Objective To examine the pro tability of variable rate seeding of corn using information about crop yield in relation to planting density crop response functions by yield potential Methods A spreadsheet model was developed to determine the pro tability of varying seeding rates for corn Data from Pioneer HiBred agronomic reports was used to estimate corn yields Yield potential zones varied corn yield response in the model It was assumed that yield potential zones varied spatially and that these zones were mapped High medium and low yielding zones of were considered 180 120140 and 107 less than 100 buacre respectively Three seeding rates were compared A uniform seeding rate achieved a plant population of 28000acre This treatment was the control Treatments compared with the uniform seeding rate were variable rateagronomic rule and variable rateeconomic rule The former rate was based on Pioneer recommendations Seeding rate recommendations for low medium and highyielding zones were 18000 28000 and 30000 respectively The variable rateeconomic was based on the economic criteria of marginal returns The marginal value of the additional product must be equal to the marginal cost of the extra input in each management zone Seeding rates for this scenario were 20000 26000 and 30000 per acre for low medium and highyielding zones respectively Price assumptions included corn at harvest 3bu seed 67bag dryer fuel 050gal variable rate controller and monitor 9500 with a 5year life span and interest rate 10 A 1000acre field planted with corn was assumed as well Only seeding rate was sitespecific Only two yield zones were considered at one time for simplicity Additional scenarios included varying seed prices and variable rate equipment costs Initial simulations considered variable rate technology as the only investment Additional sensitivity analyses included costs of GPS services and additional computer hardware and software ResultsConclusion Results indicated that farms with some lowyielding land lt100 buacre economically benefited from variable rate planting However these benefits vary depending on the low medium and highyielding land ratio Both variable rate planting strategies showed modest 10 returns on lowyielding land Results of the baseline scenario produced the largest returns at 4acre when the lowhighyielding land ratio was 19 for both VRT seeding strategies Seed costs savings between 50 and 110 were realized when the ratio of low to highyielding land was larger Uniform rate planting was economical for fields with medium and highyield land mixes since variable rate seeding strategies resulted in net losses during trial runs Table 24 Reported returns from variable rate seeding strategies VRTagronomic VRTeconomic decision recommendation rule Percentage of field low or a r yr mediumyielding Low yield potential land 10 047 050 50 216 232 90 385 415 Medium yield potential 10 005 000 50 044 022 90 083 043 Return to Table Listing Crop corn 108 Technology VRTplanting Region Midwest LowenbergDeBoer J 1998 Precision agriculture in Argentina Earth Observation Magazine Spring p MAl3MA15 Return to REFERENCES Objective To describe the adoption process of precision agriculture in Argentina Constraints facing Argentinean producers are discussed such the piecemeal incorporation of precision agriculture components and different government support structures in uencing agriculture in Argentina Methods Personal observation interviews with Argentinean producers and survey of production data from research stations are summarized to provide a picture of the state of precision agriculture in Argentina ResultsConclusion At least four differences distinguish adoption of precision agriculture in Argentina from the United States there are higher investment costs more risk less managementinduced soil variability and the propensity to higher custom operators Because higher interest rates obstacles obtaining credit and higher technology costs and risks dissuade investment Argentina The author estimates that producers will adopt precision agriculture components such as yield monitors and other informationgenerating devices more readily than variable rate applicators since the devices can be retrofitted to extant machinery and can be used for multiple purposes Adoption of technologies useful for mapping seems ideal since management decisions are made from an offfalm and not directly by those working on the tractor Approximately 12 of the combines in Argentina are equipped with yield monitors compared to 4 in the United States Spraying guidance systems using GPS are spreading rapidly but variable rate spreaders are not As more acres are farmed the costs of GPS units and yield monitors will decrease since per acre costs are lowered Apart from socioeconomic structures training operators how to use these new technologies data interpretation adapting variable rate technologies to the Argentinean landscape and developing a local data pool challenge development of precision agriculture in Argentina Crop na Technology precision agriculture Region Argentina LowenbergDeBoer J 1998 Adoption patterns for precision agriculture Agricultural Machine Systems SPl383 Society for Automotive Engineers Warrendale PA September 1998 Return to REFERENCES Objective To describe the adoption process of agricultural technology Attention is paid to the history of hybrid seed and tractors in the United States Constraints impeding adoption of precision agriculture are outlined 109 Methods Historical references are cited A primer on technology adoption theory is provided then adoption patterns of precision agriculture are tted to the familiar quotSquot curve Where precision agriculture is located on this curve and why is explored Future directions are forecasted ResultsConclusion Precision agriculture is not a new concept The technologies that de ne it in the context of modern capital intensive industrial agriculture are Producers are faced with a menagerie of technologies such as GPS GIS yield monitors variable rate applicators grid soil testing and computer hardware and software needed to process and manage the voluminous amounts of data potentially available using these technologies The current state of acceptance of precision agriculture is analogous the adoption of the tractor and its evolution from steam to fuelpowered and stepwise acceptance by agricultural regions What sets precision agriculture apart from other technologies that revolutionized agriculture is that precision agriculture is a composite of technologies not one package The technology is still new and producers purchase one or two components then modify them according to their own management styles That precision agriculture is information technology applied to agriculture implies data acquisition and management New forms of data and large amounts of it are now readily available But storage and acquisition of this information is a new cost not usually anticipated by producers wishing to incorporate precision agriculture into their operations Information ownership is also an issue Though producers might pay for grid sampling or mapping services they may not be capable of storing the data Institutions or private organizations are presently bettered equipped to handle these kinds of data structures Furthermore pooled data could be beneficial at regional levels Information could be used to confirm environmental problems and solutions with eXtemalities related chemical output or ef uent Risks not directly related to precision agriculture hinder its adoption Agriculture is an increasingly risky enterprise in itself with reduced government price stabilization Factors in uencing technology adoption patterns are age J 39 risk 1 JJ39 costs learning costs how to use the technology and 1 ofthe 39 39 J by ies r Crop na Technology precision agriculture Region Midwest US LowenbergDeBoer J 1998 Economics of variable rate planting for corn Precision agriculture proceedings of the 4th international conference July l922 St Paul MN p 16431651 ASNCSSNSSSA Return to REFERENCES Objective To investigate the profitability of variable rate seeding of corn information about crop response to plant populations Return to Table 9 110 Crop corn Technology VRT Region Indiana LowenbergDeBoer J 1998 What price is right Farm Chemicals 1614 2023 Return to REFERENCES Objective To clarify the why custom fees for precision agriculture services varies across the Midwest Methods The author reviews price variations across the Midwest for precision agriculture services Prices are quoted from producers who have bought products or from dealerships ResultsConclusion Grid sampling fees vary depending on the size of the grid the number and types of soil tests taken the sampling density and if eld mapping is recommended The type of J 391 used T 39 r attached to the sale package whether map making is recommended and whether the fee is applied to the entire eld or just where prescriptions are applied determine variable rate application fees Return to Table 9 Table 25 Costsacre of various services offered by dealerships Soil TestLaboratory Singleproduct VRA VRA for dry fertilizer Entire Package 160333acre 100300acre 0500acre 39acre4 years over a four year period Variable rate application computer controlled Includes grid sampling variable rate fertilizer application and maps Return to Table Listing 111 Table 26 Annual returns to producers for different combinations of common precision agriculture practices The values show how these fee levels affect the pro tability of each practice when used as a stand alone technology As practices become more integrated returns are stabilized Returns to VR P K VR application VR of lime 3 VRT application Producers Application 3 of P K by soil acre grid of N P and K acre grid type plus VR planting Low 733 211 062 1108 High 1313 364 131 1721 Variable rate Return to Table Listing Other feedetermining factors include the level of investment put into the technology used the number of clientele in a region local marketing strategies and customer demand Uncertainly whether precision agriculture is worth its cost stems from problems demonstrating differences confusion generated by university studies stemming from disagreement or lack of consensus about experimental design and analytical frameworks using input savings as the primary measure of pro tability and high expectations Spreading costs requires that a producer sign up for programs offered by dealerships The author concludes that the economics of precision farming are themselves site speci c Crop na Technology VRT grid sampling Region Midwest LowenbergDeBoer Jess 1999 GPS based guidance systems for farmers Purdue Agricultural Economics Report December 1999 p 89 Return to REFERENCES Objective To describe the multiple uses of GPS in precision agriculture Methods The author combines personal experience with testimonial to highlight the advantages of GPS as well as the costs associated with adoption of this technology ResultsConclusion Comparing GPS guidance with conventional foam marker systems 0 GPS is more accurate at higher speeds works with spinner spreaders Allows for guidance over growing crops GPS is less affected by weather or uneven terrain no bounce GPS has lower recurng costs reduces operator fatigue GPS is easier to set up Reduces chemical use by reducing overlaps Easily generates asapplied maps and Decreases the need to reenter sprayed areas 112 GPS may be cost prohibitive for some producers Custom applicators cost roughly 14500 For producers who have GPS guidance components cost 3000 A basic GPS system with a lightbar display a position indicator costs 7000 Foam marker systems costs range from 900 to 2800 The currently estimated time it would take to recover GPS costs is 3 years Table 27 Comparison of returns from foam marker and GPS systems Item Foam GPS guidance Lightbar only marker Costs Purchase price 1000 7000 3000 Useful life 5 3 3 Annualized cost yr 264 2815 1206 Recurring cost Foam yr 336 0 0 Differential correction yr 0 800 0 Annual cost yr 600 3615 1206 Annual cost ayr 020 120 040 Bene ts in reducing overlap of area overlapped 10 5 5 Overlap acres 300 150 150 Opportunity costs sprayer applicator a 440 440 440 yr 1320 660 660 Extra chemicalfertilizer yr 3000 1500 1500 Overlap cost yr 4320 2160 2160 Overlap cost ayr 144 072 072 GPS net benefit 029 052 RETURN TO INTRODUCTION Table Listing or Table 9 Crop any Technology GPS Region any ll3 LowenbergDeBoer J 1999 Adoption of GPS based guidance systems in agriculture Successes in precision agriculture proceedings of the 4 annual conference Brandon Manitoba November 1999 Return to REFERENCES http dm amoecnpurdueeduNbiehlSiteFarminpublicationshtml Objective To provide an overview of the advantages of GPS systems Prices for this technology are provided as well as a partial budget outlining the bene ts of GPS compared to foam marker systems Methods The author uses testimonial from usergroups Some refereed journals support comparative statistics between GPS and foam systems ResultsConclusion GPS is more reliable and accurate than foam marker systems GPS also allows farmers to use specialized technologies such as spinner threaders The technology is relatively easy to use is less affected by weather takes less time to set up and allows the operator to continue work when visibility is poor GPS systems have few to no recurring costs Some companies presently provide free update services The largest recurring cost for the GPS system is satellite differential correction 800 year 39 1 Many users have found this fee to be less than costs of foam Producers owning yield monitors found that the recurring costs associated with satellite differential correction are offset when these technologies are used in tandem Chemical waste is also reduced using GPS since it is more accurate than foam markers A partial budget comparing foam markers and GPS includes purchase costs machinery longevity annualized and recurring costs direct benefits ie reduced overlap percentages as related to chemical savings and operation costs Partial budget results indicated a modest advantage of custom applicator GPS systems 14500 over foam marker 7000 systems 010030 when custom applicators are engaged For producers return from GPS systems were higher than those from foam marker systems 052 when lightbar technology 3000 was considered distinct from GPS guidance partial budget results for GPS systems When GPS guidance 7000 was compared with foam marker systems as used by producers only returns were negative 029 Crop an Technology GPS Region any LowenbergDeBoer J and Anthony Aghib 1999 Average returns and risk characteristics of sitespecific P and K management eastern corn belt onfarm trial results Journal of Production Agriculture 122 276282 Return to REFERENCES Objective To provide an economic assessment of sitespecific management SSM of P and K as applied to corn soybean and wheat production by l comparing net returns of SSM managed fields compared to whole field management WMF strategies for PK inputs 2 determine whether PK fertilizer use decreased with SSM 3 whether risk averse farmers preferred SSM techniques over WFM strategies 4 determine whether or 114 not differences exist between expected returns and risk pro les when grid and soil type management strategies are compared Grid and soil type analysis represent SSM techniques Methods Onfarm trial data 1993 to 1995 from six farms was compiled then used to determine the variability of returns from SSM and whole eld management WFM elds ANOVA was used to statistically compare differences between WFM grid and soil type management SSM Stochastic dominance analysis was used to rank areas beneath cumulative distribution curves of crop returns in terms risk aversion ResultsConclusions That SSM will decrease fertilizer use cannot be supported by the ndings of this experiment The total amounts of P and K applied throughout the study did not correspond with either SSM method used In terms of average returns fertilizer applications based on soil type had the highest returns at B 025 The authors interpret the results of their meanvariance and SD analyses to indicate that these ndings provide a basis albeit tentative for understanding the risks associated with SSM technology SSM technology reduces risks associated with production However SD and mean variance results were not significant at the 5 level of signi cance Return to Table 9 Crop Corn soybean wheat Technology VRT P and K grid and soil type management Region Ohio Michigan Indiana LowenbergDeBoer J 2000 Economic analysis of precision farming In Agricultura de Precisao Borem Aluizio Marcos Giudice Daniel Marcal Evandro Mantovani Lino Ferreira and Reinaldo Vale e Gomide eds Federal University of Vicosa Vicosa MG Brazil Return to REFERENCES Objective To discuss the fundamental methods for the economic analysis of precision agriculture at the farm level Methods Recent literature is reviewed discussing the global state of precision agriculture Factors to consider while studying the economic feasibility of precision agriculture are discussed as well as the conditions whereby precision agriculture technologies are likely to be adopted ResultsConclusion Of central focus in this report is how to incorporate the value of information and the costs of its collection into a unsubstantiated reports analysis of precision agriculture Information is viewed as any other input involved in the farm production process The author calls for a more complete profitability analysis than previous partial budget analyses conducted for precision agriculture This would include whole farm impacts and impacts on the yield and cost risks producers face The time period of the usefulness of information such as yield maps or soil tests needs to be assessed as a depreciable asset Information related costs include grid soil sampling and laboratory analysis purchase of digitized soil maps software and computer hardware 115 yield map making and training personnel to understand and implement these technologies These costs need to be dispersed over acreage falmed and time Other problems associated with estimating the pro tability of precision agriculture include accurately measuring yield gains inappropriate experimental designs detecting subtle differences in yield quality or quantity the speci city of farming operations the need for holistic systematic analyses and incorporating external offfarm bene ts Using partial budget data from other sources the author demonstrates that positive generated by precision farming 4701ha Return to Table 9 Crop na Technology VRT precision agriculture Region global LowenbergDeBoer J and Alan Hallman 2000 Value of pH soil sensor information Paper presented at the 51 International Precision Agriculture conference Minneapolis MN July 2000 Return to REFERENCES Objective To investigate optimal liming rate levels using an automated sensor A unsubstantiated reports analysis is provided Methods A model was developed to compare returns from pH tests conducted manually or with a machine equipped with an automated sensor Corn yield in response to pH was modeled using a quadratic response function A pro t equation was derived to compare returns from manual and automated pH readings and subsequent liming rates based on these ndings A grid matrix was assumed in the model Each grid in the hypothetical eld was 25 acres Lime application was varied per grid based on recommendations Uniform and variable rate applications were compared in addition to the pH sampling methods ResultsConclusion Simulated results indicate that the pH sensor is more accurate than manual pH tests Modest returns were also greater for the sensor than they were for the manual test method However because of the novelty of this technology it is currently costprohibitive It is more likely that producers will customhire this service or rent the equipment Crop corn Technology VRT limepH Region Midwest Macy Ted S 1993 Macy farms 7 sitespeci c experiences Soil speci c crop management proceedings ofthe lst workshop P 229244 ASNCSSNSSSA Return to REFERENCES 116 Objective To describe the outcomes of VRT on a working farm specifically the effects of variable application rates its implementation and the nancial impact this practice had on returns Methods The author describes the operational procedures of a hightech farm A list of constraints faced by the operation impeding adoption of sitespecific management technology was provided along with the remedies used to overcome these obstacles Using soil survey maps prepared by the USDA and grid soil fertility testing 25 acresgrid 330 ft x 330 ft the farm manager decided upon which fertilizer N rates should be used over 1000 acres of crops corn These maps along with a GIS crop management software package was used to determine timing and rates of fertilizer application and seeding A simple return minus costs was provided to demonstrate the profitability of sitespecific management strategies for this case study ResultsConclusion This farm has successfully adopted sitespecific management techniques to its operation The adoption process according to the author has been ad hoc Incorporation of sitespecific management technologies such as variable fertilizer applications and seeding entailed adapting existing technologies such as GIS GPS and chemical applicators to extant management practices The farm manager developed some software programs himself including the master controller software used to monitor field activities inhouse This program allows the controller to monitor vehicleapplicator position in real time A budget is provided in the report It suggests that sitespecific management technology is cost effective for this operation In fact a total saving of l4acre was achieved although average yield goal of corn was reduced by 18 bushels However a more detailed budget would have included an itemized list of the implements bought learning curve lag times soil sampling costs and computer hardware and software purchased and developed Crop corn soybean Technology VRT Region Indiana Mahajanashetti SB Burton C English and Roland K Roberts 1999 Spatial break even variability for custom hired variable rate technology adoption Selected paper for the annual meeting of the American Agricultural Economics Association Nashville TN Aug 811 1999 Return to REFERENCES Objective This report has three main objectives First to quantify the amount of spatial variability in fields with two or more soil types economically justifies VRT implementation Second how much spatial variability in a field is needed to maximize VRT Lastly to determine the impact of VRT on crop and input prices Methods Corn and nitrogen mean prices 279bu and 026lb respectively from the Tennessee Department Agriculture 19931997 were used in the model to determine returns from VRT Estimated VRT charges were 300acre Fertilizer N application 117 using VRT was 200acre more than uniform application methods plus an additional 100acre charge for soil maps Three land types classified elds lowyield medium yield highyield soils Iterations tested which combinations of soil types as ratio percentages yielded returns above VRT investment costs or breakeven prices ResultsConclusion Fields with low and highyield response soils had the most frequent returns above investment At 56 lowyielding soils 44 high yielding returns were highest at 707acre This scenario was valid for fields with a surface area of 1590 lowyielding soils 8510 highyielding soils Eleven other economically viable combinations were determined with returns above VRT costs ranging from 089 to 403 The medium and highyielding soil combination had positive returns on investment when mediumyielding soils covered 12 to 58 of the field and highyielding soil coverage was varied Positive returns on investment were found for lowyielding soils in combination with high yielding soils when 7 7 22 of the field was covered by highyielding soils and low yielding soils were varied When mediumyielding soils were varied in combination with highyielding soils positive returns were generated when values ranged from 9 to 73 highyielding soils and 20 mediumyielding soils and 753 highyielding soils in combination with 40 mediumyielding soils The economically viable range of spatial variability decreased with decreases in corn and nitrogen prices Conversely increases in corn prices expanded the spatial variability of lowyielding land Crop corn Technology VRTN modeling Region Tennessee Malzer Gary L 1992 The changing technology of variable rate fertilizer application Unpublished document Soil Science Department University of Minnesota Return to REFERENCES or Table 9 Objective To quantify corn yield variability to estimate the yield response of applied N in different areas of a field and to determine which soil quality characteristics offer the best information for determining variable N application rates A partial budget is provided analyzing the profitability of VRT nitrogen management Methods Two field locations were used in the evaluation of variable rate nitrogen application Soil surveys were conducted at all sites within the field at a scale of 15000 Soil was sampled in 100foot grid patterns 4 samplesacre Soil pH nitrate and ammonium N organic C and N and estimated of mineralizable N were determined Four N rates were determined the variable treatment and compared to a uniform conventional treatment Threedimensional field maps represented the spatial variability of soil fertility and N distribution and yield potential ResultsConclusion Nitrogen fertilizer returns for the variable rate strategy based on yield maps and mapping units were greater at both sites 126 and 51acre than returns 118 from the conventional treatment 108 and 27acre respectively Returns from the VRT treatment where N recommendations were based on soil test were intermediate between these treatments 117 and 30acre Crop corn Technology VRTN Region Minnesota Malzer GL PJ Copeland JG Davis JA Lamb PC Robert and TW Bruulsema 1996 Spatial variability of pro tability in sitespeci c management Precision agriculture proceedings of the 3rd international conference June 2326 Minneapolis MN p967975 ASNCSSNSSSA Return to REFERENCES Objective The authors evaluate the pro tability of sitespeci c management Pro tability is de ned as the potential net return that could be expected with ideal site speci c management conditions Methods Four corn 5ha elds comprised mainly of clay and loam were treated with six Napplication rates 0 67 101 135 168 and 202 kgha A splitblock was used as the experimental design with each treatment replicated six times Treatments were randomized within each block Yield monitors were used during harvests Economic optimum N rate EONR was de ned as the rate at which the marginal costs of N application rates were equal to the marginal returns Semivariograms were used to analyze spatial correlation in all elds A simple return minus costs table evaluated the pro tability of the treatments ResultsConclusions Current N recommendations by the University of Minnesota overfertilized a eld by 45 and underfertilized another site by 35 Expected yields produced from both management strategies produced similar results According to the results the added value of VRTN is on the order of 10 to 20 A variety of crop response functions within a given eld indicated that some areas of any given eld continued to respond to high N application rates while other regions of a eld needed little to no N These response cum regression equations were used for EONR analyses EONR results varied within and between sites The authors conclude that grouping response data into response regions is only effective if accurately re ects the observed data in the sub zones that make up regions and if it provides a reliable error estimator within the sub region Additionally to yield maps may be highly correlated but differences in spatial arrangements may be different Actual returns must include the costs of technology adoption absorbed by the farmer and the capability of making a decision base on information generated by the activity The authors do not include these costs and hamstring their analysis However the authors state that the methodology they used to determine the EONR and pro tability of VRTN is easily adaptable to other components that make up the VRTN technology bundle especially management combinations Return to Table 9 119 Crop corn Technology VRTN Region Minnesota Mann John 1993 Illini FS variable rate technology technology transfer needs from a dealer s viewpoint Soil speci c crop management proceedings of the 1st workshop Madison WI p 317323 ASNCSSNSSSA Return to REFERENCES Objective To describe how a commercial dealership made sitespecific management technology more affordable to producers Methods The dealership offered VRT to farmers using a twostep process Phases I and II Phase I included grid sampling soil test production of a hand drawn map to show where samples were taken a kriged map showing P K and pH distribution throughout the field and a digitized map showing resulting management zones and a kriged map showing application rates No economic analysis was presented ResultsConclusion One advantage of VRT is that it compels the salesman to interact with the producer making fertilizer plans This in effect helps promote the technology as well as educating farmers about it After three years implementing this program the returns to the company have been middle of the road The startup costs were higher than anticipated and returns have not yet compensates for this expense The amount of business catering to VRT mapping was overestimated However the demand for VRT by farmers was underestimated Notable constraints faced by the dealership include 1 little yield information exists economically justifying VRT 2 the project costs money 3 a successful VRT project depends more on people not technology and 4 VRT must be publicized using extension or other techniques Crop corn soybean Technology VRT Region Illinois Marks Robbin S and Justin R Ward 1993 Nutrient and pesticide threats to water quality Soil specific crop management proceedings of the lSt workshop P 293299 ASNCSSNSSSA Return to REFERENCES Objective The authors describe how fertilizer and pesticide use threaten groundwater reserves and how soil specif1c management can alleviate groundwater contamination Methods The authors review data produced by the EPA and other sources ResultsConclusion The authors conclude that soil specific management could potentially reduce point source pollution According to the authors the benefits of soil specif1c management will not be realized unless it is regulated as policy regulating the 120 promotion of prudent chemical input levels in agriculture Recognizing that adoption of this particular technology is cost prohibitive they foresee government loans to small or medium scale farmers playing a role in the dissemination of the technology Another remedy would be creating policy that required farms to keep detailed records of chemical inputs Crop various Technology soil speci c management Region any McBratney AB and BM Whelan 1995 Continuous models of soil variation for continuous soil management Sitespecific management for agricultural systems proceedings from the 2quotd international conference March 2730 Minneapolis MN p 325338 ASNCSSNSSSA Return to REFERENCES Objective The authors propose a model for understanding continuous soil variables and corresponding spatial heterogeneity The model is based on fuzzy data set theory The cost effectiveness of information derived from such a model is presented Methods Conventional interpretive methods used to make recommendation for fertilizer applications were compared with soil map interpretations using fuzzy logic Financial returns generated by a onedimensional conventional model were compared to returns generated using an autoregressive fuzzy model A simple return minus costs table evaluated the profitability of these diagnostic techniques ResultsConclusion Simulated results indicated that returns from recommendations based on information processed using fuzzy logic were greater than returns from conventional interpretive methods The authors conclude that fuzzy soil maps provide a more accurate description of soil variability In addition the authors emphasize the importance of including real time data in addition to auxiliary data in order to use soil maps effectively for sitespecific recommendations The economic analysis provided by the authors is incomplete The only figures used in the economic analysis were returns from yield and costs of Pfertilizer The budget did not include the costs of implementing this technology the costs of gathering and analyzing information or additional costs such as human capital Crop sorghum Technology soil mapping Region na McBratney Alex B Brett M Whelen James A Taylor and Matt J Pimgle 2000 A management opportunity index for precision agriculture Proceedings of the 51h International Conference on Precision Agriculture and Other Resource Management July 1619 2000 Radisson Hotel South Bloomington Minnesota USA Return to REFERENCES 121 Objective To develop an opportunity index Oc that quanti es whether sitespeci c management SSM strategies are the best way to manage farm resources based on crop and yield variability The 0c is based on 1 the magnitude of yield variation 2 the spatial structure of yield variation relative to the minimum capability of currently available variable rate spreader technologies and 3 economic and environmental bene ts compared to conventional management techniques No economics are presented in this report Methods Yield monitor data 19951999 from 20 harvests over 16 elds producing grapes wheat cotton lupins or sorghum was collected then used to establish an Oc All crops were managed using quot 39 r 39 39 1 Three general components described the model magnitude spatial structure and economicenvironmental bene ts Each component was broken down into a system of equations representing autocorrelated yield variations empirical variograms and a dummy variable representing magnitude spatial structure and environmentaleconomic bene ts respectively The 0c is the square root of the product of each component ResultsConclusion The Oc values for the 20 yieldmonitored elds ranged from 28 to 472 Differences between high and lowyielding portions of elds decreased concomitantly with decreases in 0c The authors suggest that Oc s greater than 20 indicate that conditions may be appropriate for producers to adopt SSM technologies Crop grapes cotton lupin wheat sorghum Technology VRT Region Australia Norton George W Scott M Swinton 2000 Precision agriculture global prospects and environmental implications Paper prepared for the 24Lh conference of the international association of agricultural economists Berlin Germany August 1319 2000 Return to REFERENCES Objective To expand upon the de nitions of precision agriculture who is using it and in what regions The authors ask whether precision agriculture is suitable only in developed countries and to what extent precision agriculture can impact markets What environmental bene ts precision agriculture will provide is examined as well No unsubstantiated reports or partial budget analyses are provided Methods The authors draw upon recent literature data sets and professional opinions to examine what precision agriculturerelated technologies have been adopted by producers why these technologies were adopted and in what regions ResultsConclusion There are three major components of precision agriculture appropriate levels of information collection information processing and interpretation and timely implementation of information as a crop management decision at an 122 appropriate scale Precision agriculture technologies are developmentspecific or site specific The former focuses on predictive models such as crop growth response to fertilizer application or pest damage The later relates to models that estimate technology adoption rates factors that in uence decisionmaking opportunity costs and the extent to which a producer discounts the future The authors suggest that early adoption of precision agriculture is likely to occur in regions where agricultural land and capital are abundant In 1996 roughly 9 of US corn growers representing 19 of the total corn acreage had adopted one or more precision agriculture components In 1998 Grid and mapbased soil sampling techniques and yield monitoring were the most frequently adopted technologies 18 followed by variable rate VRT fertilizer application 11 3 VRT pesticide application and 2 for VRT seeding Producers will adopt precision agriculture technologies when they are profitable and adoption is more likely to occur with high value crops such as potato and sugar beets The authors mention the importance of human capital in the adoption process especially in terms of the level of education of a producer and their ability to understand the value of information and how to use it Crop na Technology VRT Region na Nowak Peter J 1993 Social issues related to soil specific crop management Soil specific crop management proceedings of the 1St workshop P 269285 ASNCSSNSSSA Return to REFERENCES Objective The author defines the social conditions necessary for in uencing adoption rates of crop management technologies 1 the form of the technological package 2 the physical resource base wherein the technology is to be applied 3 the profile of human capital and farm firms in the region where the technology is to be applied and 4 the institutional support network Methods The author summarizes current research for each antecedent condition of site specific management technology adoption ResultsConclusion The author discusses in detail the four necessary antecedents of soil specific technology adoption For explanatory purposes each domain is broken down into subcategories The first domain the nature of technology is comprised of an information base positioning techniques and application processes The author points out that each of these technology bundles is regulated to one degree or another by the law of diminishing returns given any context there is a point where the costs of implementing these technologies will outweigh the benefits The sections that follow examine the factors making up these variable socioeconomic and environmental contexts The relation of technology to the adoption process discusses five central characteristics useful for classifying adoption of new agricultural technologies 1 relative advantages to economic benefits and social status 2 compatibility of the new technology to the 123 existing array of technology 3 how complex the new technology is 4 the ability of the technology to be tried by farmers on a small scale and 5 how observable results of the new technology are The second domain 7 physical resource characteristics 7 describes the variability of soil pro les not only across the US but the fact that within a given eld soil pro les can be highly variable The author alludes to the fact that the more variability there is in a given eld the greater the costs will be of soil speci c management and that soil characteristics will be the determining factor of the technology that will be used The third domain 7 human capital pro le 7 brings to attention that new technologies are always introduced into a context of preestablished routines behaviors and values These factors will in uence the acceptance or rejection of a new technology as well The fourth domain 7 social impacts 7 states that soil speci c management technologies are only appropriate for highcapital large farms unless more costeffective technologies can be provided to small and medium sized farms Furthermore that farms do not operate in a vacuum ie they are dependent on institutions outside of the farm rm is brought to attention That is adoption of soil specific management techniques will entail a group effort involving actors representing different institutions Of greatest concern for the author is the nonspeci city of the current applications of soil speci c management Although P and K protocols are well de ned N pesticide and herbicide applications remain largely undeveloped This thorough report covers sociological and physiographic antecedents necessary for soil speci c management technology adoption on a general level Important issues omitted include learning curve lag time and associated costs as well as individual preference pro les and these factors in uence acceptable risk levels of farmers The author anticipates that larger farms with high outputs greater returns and more capital will accompany soil speci c management technologies A salient topic that could be discussed would be the extemalities associated with the demise of small and medium sized farms Crop corn used as reference Technology soil speci c management Region any O Neal Monte R Jane R Frankenberger Daniel R Ess and James M Lowenber Deboer 2000 Impact of spatial precipitation variability on pro tability of sitespeci c nitrogen management based on crop simulation Presented at the 2000 ASAE Annual International Meeting Paper No 001014 ASAE 2950 Niles Road St Joseoph MI 490859659 USA Return to REFERENCES Objective To determine how precipitation variability across space impacts farm management decisions The economic variable used to gauge the impact of spatially variable precipitation was Nfertilization management Methods Four Nmanagement strategies were compared Under both variable VRT and uniform rate URT Nmanagement strategies 40kg of starterno starter N 124 application were compared Onehectare grid cells were assumed and yield data was simulated using DSSAT 35 Precipitation data included onfarm data the closest NWS station and the mean of the three nearest nonmetro NWS stations Resulting model parameters serviced from existing crop data were used to simulate production for 20 years with a 2year comsoybean rotation Four 50acre plots supplied existing crop data Yield potential was estimated based on the previous ve years of corn production data Onehectare grids demarcated sitespeci c zones of the plots Pro tability was estimated using stochastic dominance and sensitivity tests including VRT application costs corn price and fertilizer costs as variables A detailed table provided the values used to calculate pro tability ResultsConclusion Simulation results indicated that onfarm data was consistently the most reliable and pro table information source regarding precipitation and how it impacted N management decisions The simulation model revealed that a nostart N management approach was most pro table It also revealed that keeping track of onfarm precipitation is not pro table The authors warn however that other factors more than likely contributed to this result than precipitation alone For example they posit that the activity of or ability to access NWS weather information and historical databases ie good farm management practices may have been more of a determining variable than precipitation itself Crop corn soybean Technology VRTN Region Indiana Oriade Caleb A Robert P King Frank Forcella and Jeffrey L Gunsolus 1996 A bioeconomic analysis of sitespeci c management for weed control Review of Agricultural Economics 18 523535 Return to REFERENCES Objective To explain how quality pest management information gained by including weed distribution patterns enhances producers weed management decisions The economic and environmental bene t as a low input weed control strategy is examined using as bioeconomic model Methods The authors modi ed a riskneutral static weed management model Variables such as crop yield weed control decisions variables weed population density herbicide effectiveness and yields where no weeds are present represent the relationships between the biological components of weed management and the production function of crop yield The model estimates expected net returns for a speci ed number of years using annual net changes in weed seed bank populations ResultsConclusion Simulation results indicated that sitespeci c weed control is not cost effective when weeds are evenly distributed over a eld When there were low levels of patchiness returns from sitespeci c management were negative For soybeans there was a slight return of 300acre At moderate weed levels economic and 125 environmental bene ts are modest yet positive for both crops The authors assume that the returns form sitespecific weed management for corn is not worth the effort when weed patchiness is moderate At high levels of weed patchiness and pressure variable weed control becomes economically and environmentally bene cial especially when interventions are implemented during pre and postemergence stages of weed growth The authors conclude that returns from sitespecific management that is less than 300acre is not sufficient to warrant the practice The costs of information collection time effects and human capital were not considered in the model How weed distribution over a field would be assessed was not addressed Return to Table 9 Crop corn soybeans Technology VRTherbicides simulation Region Minnesota Oriade CA and MP Popp 2000 Precision farming as a risk reducing tool a whole farm investigation Proceedings of the 5 Intemational Conference on Precision Agriculture and Other Resource Management July 1619 2000 Radisson Hotel South Bloomington Minnesota USA Return to REFERENCES Objective To investigate the potential of precision falming PA as a riskreducing utilitymaximizing tool within a wholefarm planning context Methods A quadratic risk programming model subject to constraints was devised to create a set of farm plans that border an expected valueutility limit The function was designed to maximize gross production margins above cash expenses less the product of a risk aversion coefficient and a risk premium The risk premium is simply the variance of net returns produced under a management strategy The risk aversion coefficient is twice a standardized normal Z value at a specified level of significance or divided by the standard deviation of the risk premium Data from Arkansas wheat and cotton production from 1990 to 1997 were used to generate gross margin means and variances for risk modeling net returns to land risk equipment and other production activities Fixed assets depreciation was not incorporated into the model ResultsConclusion Under riskneutral conditions PA is the optimal production strategy for soybean and rice production As the magnitude of risk aversion was increased during simulations proportions of crop mixes planted per unit area changed as well as increasesdecreases in gross margin This indicated that producers would be willing to accept some loss in revenue provided variation in returns decreased The degree of gross margins of optimal management choices is inversely related to the level of risk aversion The authors conclude that there is little evidence to suggest that PA is feasible risk reducing strategy in wholefarm management planning The authors suggest riskaverse farmers act to reduce wholefarm gross margin variability As such PA will compliment and not replace conventional management strategies Crop soybean wheat rice Technology VRT 126 Region Arkansas Pan WL DR Huggins GL Malzer CL Douglas Jr and JL Smith 1997 Field heterogeneity in soilplant nitrogen relationships implications for sitespecifrc management In The state of sitespecifrc management FJ Pierce and E Sadler eds p 81100 ASNCSSNSSSA Return to REFERENCES Objective The authors review the factors contributing to plantsoil dynamics in two cropping systems and to assess how these dynamics affect prospects for sitespecific N management Methods The authors summarize current information regarding sitespecific N management with regards to soil variability and fertilizer N efficiency An economic analysis is presented in budget form ResultsConclusion Complex relationships between edaphic and climatic factors confuse understanding of N cycling and fertilizer N efficiency This complexity complicates production of N fertilizer responses For example a 37yr study in Minnesota found that 67 of the variation in corn production was attributable to yearto year climatic variations Only 15 of production was attributable to direct control ie fertilizer application especially N Thus yeartoyear yield goals prediction based on climatic variations are largely unreliable Economic optimum yield EONR varied with each location In some cases application rates based on EONR were below the recommended rates promoted by extension agents In other cases rates were much higher than those prescribed for conventional application protocol ie fixed or uniform rates Returns from variable N rates applied over a field were costeffective only in some circumstances The authors suggest that further research in terrain and hydrologic modeling will compliment and bolster VRTN technology especially in the field of forecasting variable N rates Crop wheat corn Technology VRTN Region Washington Idaho Minnesota Pannell DJ and AL Bennett 1999 Economic feasibility of precision weed management is it worth the investment In Precision weed management in crops and pastures Eds RW Medd and JE Pratley RG and F Richardson Melbourne httpwwwgeneraluwaeduauudpanneldpap9903 l htm Return to REFERENCES Objective To develop a framework wherein the benefits derived from precision weed management can be validly estimated The analysis focuses on a weed management system called Weed Activated Spray Process WASP This technology is compared to a hypothetical technology that could be used in similar contexts but with different results 127 Methods A variable rate herbicide applicator was tested using simulated data A dynamic optimization model was modi ed to incorporate machinespecific variables such as failure to spray in indicated zones misapplication rates controller error machine cost and recurrent costs and annualized costs of the equipment Probability distribution functions were determined for each of these parameters then incorporated into the model Wheat response functions based on the model were applied to a hypothetical field of 100 lha blocks Variable weed densities were assigned to each block randomly A partial budget analysis was used to determine under which scenarios WASP was cost effective ResultsConclusion The simulated results indicated that WASP technology is not a costeffective implement for applying variable herbicide rates over weedinfested fields The authors suggest that their results underscore the problems variable rate applicator manufactures face when designing new precision products Even if the WASP technology was free of any operational errors ie model error parameters were set to 0 the cost of the technology itself would still exceed the benefits Crop wheat Technology VRT herbicide Region Australia Paz JO WD Batchelor TS Colvin SD Logsdon TC Kaspar DL Karlen BA Babcock and GR Paustch 1999 Modelbased technique to determine variable rate nitrogen for corn Precision agriculture proceedings of the 4th international conference July l922 p 12791289 ASNCSSASSSA Return to REFERENCES Objective To develop a corn crop growth model that estimates yield variability and variable nitrogen recommendation rates in the same field Methods A l6ha field was divided into 8 sections each with 28 grids Corn yield was measured from each of the 224 plots Soil physical properties were determined such as drainage corridors soil moisture content organic C for several soil types Planting date final yield soil N N application date and rate from each grid covering three years were obtained The model inputs included inputs management practices variety row spacing plant population fertilizer and application dates and environmental conditions soil type daily temperature rainfall and solar radiation Twentyone N rates were evaluated Profit as returns from yield minus testing and application costs per acre in terms of optimum N rates was determined during the simulation ResultsConclusion Average profit maximizes at 190 lb Nacre Yield response for 62 of the grids was increased when higher than recommended N rates were applied 190 to 200 lb Nacre Net returns from these rates ranged from 150grid to 450 grid on low and highquality grids respectively The authors assumed a uniform nitrate distribution in their model This impacts the high optimum rate observed in the simulated results Additionally in the economic analysis only one variable was 128 considered nitrogen application rate Economic bene ts from a management practice such as variable application can be in ated when only one variable is incorporated into the model Crop corn Technology VRTN Region Iowa Pierce Francis J and Peter Nowak 1999 Aspects of precision agriculture Advances in Agronomy 67 185 Return to REFERENCES Objective To provide a historical background of precision agriculture to summarize the current state of eld and to look forward into its possible futures Methods Based on personal experience and reports from other sources directly involved with or indirectly in uencing the eld of precision agriculture the authors report the current state of precision agriculture on a general global level ResultsConclusion The authors de ne precision agriculture as quotthe application of technologies and principles to manage spatial and temporal variability associated with all aspects of agricultural production for the purpose of improving crop performance and environmental qualityquot Several factors determine the success of precision agriculture 1 the degree to which eld conditions can be known and managed 2 the appropriateness of recommendations based on this knowledge 3 variable soil weather and application controllability and 4 offfarm support infrastructures Although the concept of precision agriculture is not new it is only until recently that computer technologies have enabled public access to GIS and GPS systems the handling and processing of massive databases and free information networks by way of home computers Spatial variability is most accurately understood using GISGPS systems The development of these technologies has rekindled interest in precision agriculture However only 31 ofthe 2053800 farms 1997 in the US have home computers and 13 intemet access and precision agriculture software is not currently available in a userfriendly public form Crop na Technology precision agriculture general Region any Popp J and T Grif n Adoption trends of early adopters of precision farming in Arkansas Proceedings of the 5Lh Intemational Conference on Precision Agriculture and Other Resource Management July 1619 2000 Radisson Hotel South Bloomington Minnesota USA Return to REFERENCES 129 Objective To describe the current status of precision farming PA in Arkansas the amount sources and ef cacy of PA promotion by industry representatives and researchers and the possible future of PA in Arkansas Methods Individuals representing farmers using PA industry representatives and extension agents were interviewed by telephone N 38 Interview questions were designed to disclose 1 the extent of adoption of PA technologies in Arkansas 2 demographic pro les of early adopters and 3 respondents perceptions of PA and what directions the technology is heading ResultsConclusion Compared to the average age of early adopters of PA technologies across the US 54 yrs early adopters in Arkansas averaged 45 years of age Early adopters and industry representatives speculated that persons who adopt PA technologies expect increased revenues and decreased operation costs and improved management capabilities The authors speculate that PA adoption is driven by chronically low pro t margins associated with some conventional management strategies or that framers seek new technologies when current pro t levels are precariously low It might be suggested that individuals are more willing to adopt when they can nancially afford to change routine management practices Crop rice corn soybeans Technology PA general Region Arkansas Robert Pierre Scott Smith Wayne Thompson Wally Nelson Dennis Fuchs and Dean Fairchild 1989 Soil speci c management Unpublished document University of Minnesota Return to REFERENCES Objective To evaluate variable rate and conventional uniform N application strategies A partial budget is provided that compares the economic feasibility of VRT to conventional N management strategies Methods The study area was a 70acre eld Soil samples from three depths 06 0 24 and 2448 were tested for N P K and Zn content Test results indicated three soil fertility types high medium and low Fertilizer rates were determined from soil test results and yield potential indicated by each soil type The conventional uniform treatment applied 130 40 and 30 lbsacre of N P and K respectively Variable rate applications ranged from 50 to 140 35 to 55 and 30 lbsacre N P and K respectively Another VRT treatment using the same fertilizer schedule included a herbicide A plot receiving no fertilizer was used as a control ResultsConclusion Net returns above the check plot were 91 96 and 111 for conventional VRT and VRT with herbicide treatments respectively Corn yield was 133 139 and 145 buacre for conventional VRT and VRT with herbicide treatments 130 respectively There was an increase of 20acre with VRT inputs versus conventional applications Crop corn Technology VRTN Region Minnesota Rejesus Roderick M and Robert H Hornbaker 1999 Economic and environmental evaluation of alternative pollutionreducing nitrogen management practices in central Illinois Agriculture Ecosystems and Environment 75 4153 Return to REFERENCES Objective To examine the economic and environmental impacts of sitespeci c N management VRT and Napplication timing used on continuous corn production systems Of speci c interest was whether these practices decreased nitrogen ef uent loads from agricultural practices into the Lake Decatur watershed Methods An EPIC model was calibrated to simulate a continuous corn production system over a 40year cycle The model was also calibrated according to local hydrological characteristics and N application rates and timing based on ve soil types Nitrogen rate levels considered were 0 to 252kgha at 28kgha intervals EPIC results were compared with existing studies that provided onsite monitoring data Pro tability was determined using marginal analysis The marginal revenue from an additional unit of nitrogen was compared to the marginal costs of the application of that extra unit ResultsConclusion The authors found when N application rates increase the mean and variability of pollution also increases Mean N pollution increases most rapidly after optimal fertilizer recommendation levels have been surpassed Results demonstrate that VRT can decrease the mean and variance of nitrate pollution while concomitantly improving pro tability relative to fertilizer application As such the authors imply that VRT management might be preferable to riskaverse producers The authors conclude that VRT provides a winwin situation since producers benefit by decreasing inputs thereby increasing pro ts and reduce ef uent discharge into the environment Crop corn Technology VRTN Region Illinois Robert M ALe Quintrec D Boisgontier and G Grenier 1996 Determination of eld and cereal crop characteristics for spatially selective application of nitrogen fertilizers Precision agriculture proceedings of the third international conference June 2326 Minneapolis MN p 303313 ASACSSASSSA Return to REFERENCES 131 Objective The effects of potentially usable factors that could aid in the design of VRTN application systems were quantified The VRTN methods examined by the authors were compared to conventional N application practices No economic analysis was provided Methods A 16 and 18ha field were divided into 111 and 126 grids respectively each grid with a surface area of 144 m2 Soil depth N pH and organic matter test were conducted on each grid During the growing season each cell was divided into two sections One section implemented VTRN the other section was managed using conventional methods During the growing season the number of plants per grid was measured At harvest gross yield per treatment was determined No yield sensors were used ResultsConclusions There were no significant yield differences observed between the two experimental fields Using stepwise regression pH was eliminated from then model while soil depth and stone coverage remained Of the factors tested soil depth and crop yield had the largest coefficient of correlation Presence or absence of stones was the second most important factor useful for explaining crop yield variability When conventional and VRTN application methods were compare there were no differences in crop yield The authors conclude that yield mapping is insufficient when used alone to manage VRTN and that models designed for whole fields are not precise Although the data was not presented the authors end by stating that gains to the farmers would only be about 4000ha when comparing VTRN to conventional nitrogen application methods Crop wheat Technology VRTN Region France Roberts Roland K Burton C English and SB Mahajanashetti 1999 Hypothetical example of evaluating economic benefits and costs of variable rate nitrogen application Paper presented at the annual Meeting of the Southern Agricultural Economics Association Memphis TN January 80 February 3 1999 Return to REFERENCES Objective To highlight the possible economic benefits of variable rate N application compared the costs of hiring those services by demonstrating the effects of changing net inputoutput returns field spatial variability and yield response functions in a simulation model The information required to elicit and monitor these changes is incorporated into the unsubstantiated reports framework as well Methods The hypothetical corn yield function representing low average and high yielding field zones are used to generate Nrecommendations Variable rate and uniform rate application technologies are compared Corn and Nfertilizer prices 022lb and 242buacre respectively were obtained averaging 198695 data and used in a partial budget analysis A sensitivity analysis was conducted to show how changes in corn and nitrogen prices field spatial variability and yield response function parameters in uence returns above variable costs for VRT and uniform application rate technologies 132 ResultsConclusion As the proportion of lowfertility land increases the more profitable variable rate N application becomes However the converse is true Ranges between 15 poor and 85 highyielding land tend to be the pro table ratio ranges in this example When pooryielding soils covered 58 of the eld optima are maximized Using sensitivity analysis the authors conclude that larger differences between marginal products increase the likelihood that VRTN will be profitable This leads to wider choice of variable rate services options a farmer can select The authors end by stating that positive VRT returns are realized on fieldbyfreld bases only But precision agriculture has the potential to provide producers with more management decision opportunities increase yield and reduce Nfertilizer input costs Crop corn Technology VRTN Region Tennessee Sawyer JE 1994 Concepts of variable rate technology with considerations for fertilizer application Journal of Production Agriculture 7 195201 Return to REFERENCES Objective To summarize the concepts defining variable rate technology The promises and constraints of the technology are discussed A cursory partial budget is provided comparing net returns from field managed using conventional uniform fertilizer application practices and variable rate management strategies Methods The author combines personal experience and findings from other researchers to describe the components of VRT and the forms the technology may assume as it evolves in the agroindustrial farming context ResultsConclusion The author summarizes the principle issues and expectations related to VRT Consumers expect positive returns and there are environmental benefits assumed to go handinhand with VRT These expectations hinge upon being able to identify spatial variability of fertility zones within a field then being able to apply just enough fertilizer to those zones to maximize crop output For example high fertility zones may receive more fertilizer while low fertility zones may receive less Intermediate fertility zones may receive rates recommended by university or county extension offices That variable rate application is more efficient than uniform fertilizer application strategies has been demonstrated It is also assumed that by applying less N fertilizer for example there are quantitatively fewer nitrates leached into groundwater basins or streams By maximizing the amounts within field fertility zones it is assumed that the whole field management is optimized because of VRT efficiency Extemalities caused by nonpoint source pollution are also diminished hence the environmental benefit In the case of VRT as optimizing farm resources and its economic feasibility the results are mixed Uncertainty still resounds which soil sampling methods are best under which circumstances which crops VRT works best with soil sampling techniques and sampling density whose yield response functions best describe production realities and 133 what yield goal levels are reasonable using this technology In the latter case there is little data to support the assumption that VRT is environmentally beneficial Crop any corn used as an example Technology VRT Region all Schmitt Michael and Dean Fairchild 1991 Variable rate fertilizationcan the technology pay for itself Unpublished document Department of Soil Sciences University of Minnesota St Paul Minnesota Return to REFERENCES or Table 9 Objective This document describes one of the first evaluations of VRT using an experimental design The objective of the research was to evaluate the efficacy of soil evaluation techniques yield potential levels based on these results and how fertilizer recommendations based on these parameters affected yield and profit Methods Treatments included a check or control plot a conventional uniform rate treatment and a variable rate treatment Fertilizer recommendations were based upon soil sample results collected using grid sampling and yield potentials identified with each identified soil zoned Data was collected from two crop cycles ResultsConclusion Returns were greatest for variable rate treatments for both growing seasons Returns to VRT were 326 and 204acre 315 and 197acre for conventional treatments while check plot returns were 184 and 118acre for 1989 and 1990 respectively Overall lower N rates were applied to plots fertilizer using VRT Pro t analysis included the price of VRT applicators range 15 000 to 40 000 map making 040acre soil surveys 1acre and custom application charges 450 640acre which is close to 12 acre more than conventional application charges Crop corn Technology VRT Region Minnesota Schnitkey GD JW Hopkins and LG Tweeten 1996 Precision agriculture proceedings of the 3rd international conference June 2326 Minneapolis MN p977987 ASNCSSNSSSA Return to REFERENCES Objective To evaluate returns of variable rate fertilizer application strategies on com soybean rotation fields Methods Three fertilization strategies were evaluated uniform rate informationbased and variable rate strategies The informationbased strategy implements knowledge about field fertility found by conducting soil tests The variable rate technology 134 implements the information derived from soil tests then applies fertilizers at rates prescribed by management zones Return differences were compared for each treatment Fertilizer carryover effects were incorporated into the model during analysis ResultsConclusion Revenue increased when field fertility information was known On average implementing this information by varying fertilizer application rates further increased revenues compared to control plots Using informationbased fertilization recommendations increased profit by 574acre When these returns were combined with precision agriculture technology profits further increased by 328acre Return to Table 9 Crop corn soybean Technology VRT Region Ohio Silsoe Research Institute Date Unknown 1999 Yield mapping and precision farming an appraisal of potential benefits based on recent research and farmer experience Silsoe Research Institute SR1 Wrest Park Silsoe Bedfordshire MK45 4hs Tel 01525 860000 Return to REFERENCES or Table 9 Objective To summarize the benefits associated with yield mapping in precision agriculture Methods Testimonial anecdotal evidence and research are used to describe how yield mapping can be integrated into the decisionmaking processes characteristic of precision farming Examples include VRTN P K and weed management understanding soil types and how coordination of these inputs can be improved using yield mapping The objective includes building and managing a farmspecific database that can be periodically updated using yield mapping ResultsConclusion Using a yield map VRTP K application costs in lowyielding areas of one site were reduced by 1950ha Application costs only increased by 750 Yield maps and associated technologies are exible enough to be adapted for other production activities For example on the same site yield maps were also used to vary seeding rates On another site yield mapping allowed for the variable application of fungicide The area that would have received fungicide application using conventional spraying methods was reduced by onefourth which translated into input savings Yield mapping increased gross margins by 28875ha when applied to VRTliming at another Berwickshire farming company producing barely and rapeseed The article describes why yield map are a good place to begin precision farming practices Yield maps are not expensive costing between 3450ha However the information they provide is applicable to a variety of problems Once problems are identified a partial budget can be constructed to evaluate whether VRT in a specific area would be profitable According to the document soil variation is the main in uence of crop yield Knowing where low and highyielding areas exist facilitate identification of fertility zones 135 Crop mixed Technology yield mapping VRT Region general Snyder C T Schroeder J Havlin and G Kluitenberg 1996 An economic analysis of variable arte nitrogen management Precision agriculture proceedings of the 3rd international conference June 2326 Minneapolis MN p989998 ASACSSNSSSA Return to REFERENCES Objective The authors develop and economic framework to facilitate the adoption process and development of sitespecific management technologies Sitespecific agronomic data is used Methods Variable and uniform Napp1ication strategies were compared over a three year study on two sites Soil samples collected on a 55 by 55m grid determined organic matter pH elevation and soil texture Spatially distributed yield goal and soil nitrate were used to make N rate recommendations Yield goals were based on real yield maps Based on a model developed by the university soiltesting 1ab six N rates were determined and then applied to experimental plots at rates of 146 179 213 269 and 314 kgha Variables included in the statistical analysis were yield crop year available N N overapplication N underapplication elevation change in elevation organic matter pH soil texture and nitrates The estimated charge for VRT was 4276ha including lab analysis labor and data management costs ResultsConclusions Correlation between variables were unique to each site excluding relations between N overapplication and yield For every kilogram of N overapplied yield decreased by 0016 Mgha The estimated amount of total N applied to fields was always less for VRT than for uniform application strategies VRT profitability results were different for both sites and both years Both sites enjoyed one year out of two with return from VRT management The authors assume these results re ect differences in growing seasons Return to Table 9 Crop corn Technology VRTN Region Kansas Sobolik Chris J Alan Dzubak 1999 Evaluation of commercial cotton yield monitors in Georgia field conditions Precision agriculture proceedings of the 41 international conference July 1922 p 12271240 ASNCSSASSSA Return to REFERENCES Objective To evaluate the performance of two commercial yield monitor systems A brief economic analysis is provided 136 Methods Four sites were used in this study Two commercial yield monitors were tested The cost of the first system was 10630 and 6130 with and without GPS equipment respectively The second system cost 14383 and 10083 with and without GPS respectively Analytical software for both systems cost an additional 2000 After calibration sites were harvested and the accuracy of the yield monitors was compared ResultsConclusion The researchers and producers involved in the study identi ed aws in both systems First the cost of this technology were considered prohibitive by the producers even though the results as yield maps were accurate and deemed potentially useful Second the time it would take to learn how to maintain manage and operate these systems and associated software were considered daunting by researchers and producers as well The accuracy of both systems was greater when machines were calibrated to scan larger field units than smaller sections This data was found insufficient for analyzing sitespecific accuracy For cotton yield monitors are still in the research and development stage Costs of the yield monitors was included in the report However they were not compared with production data Compiling historical data from each of the three would provide data whereby returns from this technology over time could be projected Crop cotton Technology Yield monitoring Region Georgia Solohub MP C van Kessel and D Pennock 1996 The feasibility of variable rate N fertilization in Saskatchewan Precision agriculture proceedings of the third international conference June 2326 Minneapolis Minnesota p 6573 ASACSSA SSSA Return to REFERENCES Objective The objective of this research is to understand the in uence landscape position has on the physical properties of soils and what implications this has for managing soil productivity using techniques like VRTN Methods A 74 ha wheat field was divided into 12 10 X 620 m rows Each strip was further broken down into 10 X 10 m grids Soil testing was carried out before the experiment Each grid was assigned to one of three management options based on topographical characteristics and assumed wet and dry year scenarios higher elevations in the field received 90 kgha of N while low lying areas received only 30 kgha The converse was true for dry season scenarios The conventional rate was 60 kgha Crop yield was also measured ResultsConclusions Grain yields did not vary with fertilizer treatment especially in lowlying depressions However the authors note that grain yield was 10 bushelacre more in lowlying areas than in higher elevations Wet and dry scenarios and corresponding fertilizer rates were not cost effective However different fertilizer rates were cost effective when landscape was considered Although the authors provide an 137 economic analysis relating to their work it is not clear whether or not the results support the use of VRTN from a research perspective or that of a working farm Furthermore the analysis is based only upon one year s worth of data A more accurate assessment could be made with at least three consecutive years of data Additionally the yield results may be confounded since P was added to the experimental units during the experiment as well as N Whether of not this made a difference was not brought to attention Crop wheat Technology VRTN Region Saskatchewan Swinton Scott 1997 Precision farming as green and competitive Paper prepared for the AAENAEREIAMA Workshop on BusinessLed Initiatives in Environmental Management The Next Generation of Policy Toronto July 26 1997 Return to REFERENCES Objective To define precision agriculture examine its record for decreasing farm chemical ef uent and evaluate its role in increasing production efficiency Methods The author uses personal experience to define precision agriculture and the role it could play in improving environmental quality while increasing farm production efficiency and competition amongst agribusiness dealerships ResultsConclusion Eliminating waste is at the heart of precision agriculture From here production can be optimized and steps towards improving the environment can be taken However precision agriculture does not necessarily reduce input use Precision input management is practiced using a variety of methods sitespecific management grid soil sampling variable rate technology GIS and GPS systems developmental stage based management managing crop life cycles and integrated pest management None are truly standalone and efficacy of each activity is enhanced in combination with other activities For example variable rate fertilizer application is not possible without grid based soil sampling and is made more efficient using GPS guidance The second objective of precision agriculture is the substitution of physical inputs with information When weed distribution and density is known throughout a field spot spraying can take the place of wholefield treatments In terms of beneficial environmental impacts precision agriculture may have data is scarce if not nonexistent Currently only results from simulated are available for speculation In terms of competition precision agriculture is a relatively new industry where a variety of services can be marketed Services such as soil sampling lab analysis custom fertilizer application map making and data collection and management can be offered on a competitive basis Of course this would in effect strengthen the already strong vertical bond between producers and agribusiness representatives Cooperatives and large agroindustrial firms will most likely realize these relations Producer adoption of precision agriculture has been slow because of high costs of data collection machinery grid soil sampling variable applicators consultant fees and the uncertainty of returns However yield monitors are 138 currently at the forefront of the adoption wave This is encouraging for precision agriculture since yield monitors provide a foundation for understanding field spatial variability Crop na Technology precision agriculture general Region any Swinton Scott Stephen B Harsh and Mubrariq Ahmad 1996 Whether and how to invest in sitespecific crop management results of focus group interviews in Michigan 1996 Staff paper 9611 Department of Agricultural Economics Michigan State University East Lansing MI 1996 httn39 aoecnn Iih nmn J quot737rhtml Return to REFERENCES Objective To learn about producers experiences with sitespecific management and to discover what information they felt important to make decisions whether to invest in site specific equipment or services Methods A series of focus groups consisting of farmers having some little or no experience with sitespecific management SSM All invitees were interested in the subject University staff led focus group sessions Questions were presented to farmers representing each SSM experience level Interview results include each response frequency count ResultsConclusion Respondents pointed out that adopting some SSM components obliged them to purchase additional components to maximize the utility of the original equipment For example growers who had purchased yield monitors and wished to analyze their own data were compelled to buy computer hardware software and peripherals The alternative purchasing these products is to hire a consultant to analyze data Other costs incurred adopting SSM components included time down for learning how to use new equipment component incompatibility especially with software and equipment obsolescence The panel also noted unreliability of some SSM equipment as sometimesnew equipment such as yield monitors have not undergone rigorous field trials before they enter the market For respondents who were interested in adopting SSM technology this was seen as one of the major risks associated with SSM Benefits from SSM were expected more often than realized according to panel members For example farmers expected tangibly noticeable results from variable seed lime and N and P fertilizer application Although only one farmer in the discussion group had been using these management strategies Framers were also willing to experiment with some of the technologies such as yield monitors variable rate applicators and grid sampling All participants agreed that SSM technologies would provide a sense of where the farm firm was at any specific point of time during the growing season or over a decade A equipment cost range list is provided in the text Crop all 139 Technology VRT Region Michigan Swinton SM and J LowenbergDeBoer 1998 Evaluating the pro tability of site specific farming Journal of Production Agriculture 114 439446 Return to REFERENCES Objective To provide information about sitespecific management SSM especially variable rate technology VR and yield mapping in terms of its pro t potential using partial budgets The report uses actual data from nine different farm firms growing wheat andor barley sugar beets or corn Methods After a description of the technological components that make up the SSM composite for example GPS GIS variable rate applicators sensing technologies yield maps and yield monitors the authors conduct a profitability analysis using a partial budget for variable rate technology ResultsConclusion Experimental designs to appropriately evaluate SSM profrtability are lacking In the interim partial budgets are useful for analyzing positive returns from SSM The main partial budget line items guiding VR unsubstantiated reports analysis are inclusion of the increased costs associated with soil sampling and variable fertilizer application added information costs difference in fertilizer cost and revenue changes caused by crop yield The nine case studies used to generate partial budgets included the crops corn wheat barley and sugar beets Of the four crops VR was not profitable for wheat and barley Results were mixed for corn but returns were positive for VR managed sugar beets Not surprisingly high value highyielding crops are more economically responsive to VR than lower value lower yielding crops such as wheat and barley Of less importance are savings from reduced fertilizer use since many of the fertilizers used are relatively inexpensive There exists no profrtability information in the literature for four reasons Interpretation of yield maps is oftentimes subjective Secondly yield maps offer other profit opportunities besides VR Thirdly it is difficult to establish causeeffect relationships between crop yield and yield maps Lastly benefits of VR cannot be attributed solely to yield maps since farms are embedded in wider socioeconomic and ecological beyond the farm borders Yield maps are probably more important for activities other than VR In terms of VR the upshot is that yield maps do not provide as high a quality of controlinformation that other analysis such as grid sampling do However yield maps are useful for monitoring whole field improvements and can lower onfarm experimentation costs during harvest The authors recommend that individuals considering adopting SSM proceed with caution since profitability results are highly variable and that during this early stage of development technologies still need to be perfected Information will increase profitability through changed decisions but only if the consequences of actions guided by those decisions have beneficial outcomes Other unforeseeable factors impossible to take into account may negatively in uence an outcome Looking backwards the information used to make a decision may have been correct all things being equal The blame of the information 140 providing model would rest in its inability to account for risk and more importantly uncertainty Crop wheat barley sugar beets or corn Technology VRT yield mapping Region Western US Mid West Swinton Scott M and Kezelee Q Jones 1999 From data to information adding value to sitespecific data Precision agriculture proceedings of the 41 international conference July l922 p 16811692 ASNCSSASSSA Return to REFERENCES Objective The authors develop a conceptual model to examine differences between the quality of soil information generated by sampling or remote sensing techniques when sensing is more profitable than sampling and when sensing generate more consistent net returns than sampling Methods First the authors provided a linear production function for corn incorporating terms representing N fertilizer costs Then the authors derive profitability models for N recommendations based on sampling or sensing information These models place particular emphasis on profitability variance terms as they estimate the degrees of risk involved with these technologies in terms of net returns generated using these technologies ResultsConclusion There were no results based on data presented in the report Instead conclusions relied strictly upon mathematical proofs The authors conclude that soil sensing techniques generate more accurate information than sampling methods However the value of one technique cannot be ranked above the other since farmer risk preference governs which technology will finally be implemented Payoffs from sensing are greatest when l sensing results generate highly accurate soil profile information 2 when there are time constraints 3 where there are high degrees of field variability Sampling techniques were profitable when 1 sensor equipment is faulty 2 there are no time constraints 3 spatial variability is not as great Critique The profitability analysis provided by the authors was purely theoretical No actual or even simulated figures were used to support or verify the assumptions of the model they provided Crop na Technology VRT modeling Region na Swinton SM and J LowenbergDeBoer 1998 Profitability of sitespecific farming SiteSpecific Management Guidelines Potash and Phosphate Institute Series SSMG3 South Dakota State University Return to REFERENCES 141 Objective The authors ask when variable rate application has been pro table and under what circumstances Additionally the utility of yield mapping as a profitincreasing technology is examined Methods The authors use partial budgets to analyze the value of yieldmonitoring map making and variable fertilizer application A detailed list of the components that make up each of these technologies is included ResultsConclusion Partial budgets focus only on items whose costs change as a result of the introduction of a new technology Losses increased costs plus reduced revenues are subtracted from gains reduced costs plus increased revenues A comprehensive partial budget includes all variable and cash costs Oftentimes costs associated with training conferences seminars and workshops are omitted These costs should like other variable costs be averaged over time and acreage Longterm costs should be adjusted to re ect costs over one year Since sitespecific information is useful for several years its collection costs should be spread over its entire useful life just as for any depreciable asset Profitability is increased by information only if it changes decisions and yieldgains are the primary infreld source of increased revenue expected from site specific management Variable revenues need to be added in the partial budget Net present value sinking fund approaches can be used to annualize equipment costs based on a percentage over time This includes yield monitors spreaders and GPS systems Annualized costs need to be spread across acreage and time as well The authors conclude that variable rate technology is profitable with highvalue crops such as potatoes and sugar beets Reports indicate mixed results with corn Barley and wheat are not generally responsive to VRT Profitability of yield mapping has proven more difficult since results maps are oftentimes open to subjective interpretation and what a decisionmaker decides to do with the information Yield maps generate information not only about yield but also about soil fertility topography and other productionrelated variables 142 Table 28 Partial budget analysis of GPS Yield Monitor and GPS fertilizer application systems Item Unit Quantity Price Amount Change in yield BuA 1532 230 3524 Change in equipment cost per acre 10 discount rate 3 year depreciation Yield monitor Item 1 4000 00 133 GPS Item 1 600000 199 Planter controllers Item 1 500000 332 Microcomputer printer Item 1 300000 199 Total increase in 862 equipment cost Change in fertilizer cost Nitrogen LbA 0044 025 011 Phosphorus Lb A 1466 0 30 4 40 Potassium LbA 333 013 043 Sulfur LbA 217 021 046 Zinc LbA 011 236 026 Boron LbA 005 717 036 Total change in fertilizer cost 387 Change in seed cost Bags 001 9000 048 A Change in soil sampling Acre 1 500 500 cost Change in fertilizer Acre 1 500 500 application cost Consulting fee Acre 1 050 050 Net return to site Acre 1 1950 specific management Source Finck Charlene 1998 Precision can pay its way Farm Journal MidJanuary 1998 p 1013 Return to ECONOMIC METHODS HUMAN COSTS Table Listing or Table 9 Crop any Technology VRT partial budgets Region any Swinton Scott Mubariq Ahmad 1996 Returns to farmer investments in precision agriculture equipment and services Staff Paper 9638 Department of Agricultural Economics Michigan State University East Lansing June 1996 Return to REFERENCES 143 Objective Based on interviews and focus group results the authors identify what producers feel affects pro tability of sitespecifrc management These ndings are related to investments made by producers Inferences are then made about the return potential of precision agriculture given this context The authors outline additional factors that should be considered when determining the benefits of sitespecifrc management Methods A series of focus groups including farmers interested in or already practicing some form of sitespecific management The groups also included agribusiness representatives Producers participating in the meetings farmed 380 to 3000 acres All were cash crop farmers ResultsConclusion Grid soil sampling costs were the major concern of producers in terms of costs 475 to 1000acre Other concerns were unanticipated costs associated with adopting sitespecific management practices such as consulting fees data collection and analysis or computer hardware and software Producers who had purchased 3000 to 9000 yield monitoring systems found they had to invest an additional 1000 for software capable of analyzing generated data Computers capable of operating the software became another additional unanticipated cost Learning how to use these products cost producers in terms of time away from daily work tasks Some complained that technical support for these additional items was inconsistent or absent Farmers expected sitespecifrc management to increase yields by varying seed population and planting density variable rate liming and increased control of nitrogen and phosphorous fertilizers Risk management was another factor respondents felt sitespecific management could address These expectations were more often not met than realized Participants stated they were willing to experiment with sitespecific management so long as the costs were modest Farmers who had purchased yield monitors were hesitant to invest in grid soil sampling and variable rate technologies until they had more reliable proof of benefits associated with these technologies The authors conclude that prior economic analyses of precision agriculture have failed to take into consideration the hidden costs of technology adoption namely learning obsolescence of information and machinery incompatibilities and recurring costs Additionally definitions of benefits have been restricted to increased yield and reduced input costs Additional benefits such as fertilizer carryover effects the exibility of sitespecifrc machinery as tools capable of carrying out multiple tasks the longterm value of yield maps and offfarm value of information applicable to rent negotiation or data for seed or herbicide companies should be included into partial budget analyses Risk reduction should also be factored into any unsubstantiated reports analysis breakeven or partial budget analysis along with any potential environmental benefits Crop na Technology VRT precision agriculture general Region Midwest Michigan Swinton SM KQ Jones NR Miller 0 Schabenberger RC Brook and DD Warncke 2000 Comparison of sitespecifrc and wholefreld fertility management in 144 Michigan soybeans and corn Proceedings of the 5Lh International Conference on Precision Agriculture and Other Resource Management July 1619 2000 Radisson Hotel South Bloomington Minnesota USA Return to REFERENCES Objective Using data from two commercial farms the authors compare variable rate and whole eld applications of P K and lime Data was analyzed using spatial econometric techniques Pro tability was measured subtracting variable costs from gross production margin Methods Two 162ha plots under comsoybean rotation schedules on different farms were each subdivided into four blocks Each block was subdivided into four strips Sitespeci c or whole eld P K and lime applications were randomly assigned to each strip Soybean rotations were followed by corn or Vice versa depending on the site Soil profiles were characterized at each site Phosphorous potassium and lime were applied based on yield goals speci c to each site and respective subblocks Whole eld application costs 741ac were twice sitespecific application costs 1482 Custom GPS soil sampling and map making 865ha was annualized over three years at a 10 discount rate 348ha Lime costs and application was annualized over ve and seven years at 10 for both sites 021 and 026 respectively Crop prices from 1998 were used in pro tability analyses ResultsConclusion Combined results of two growing seasons failed to indicate that yields savings pro tability or yield stability bene ts were produced by sitespeci c management SSM treatments There was no measurable yield gain from SSM treatments and SSM pro tability as gross margin over variable costs was not statistically different from whole eld application strategies The authors conclude that bene ts from SSM will only be realized over time not two growing seasons Further more the elds used in the study site had been well managed to begin with Crop corn and soybean Technology VRTP K and lime Region Michigan Taylor Randal K Mark D Shrock Naiqian Zhang and Scott Staggenborg 2000 Using GIS to evaluate the potential of variable rate corn seeding Paper presented at the AETC meeting Paper N0 00AETC105 sponsored by the ASEA 2950 Niles Rd St Joseph MI 490859659 USA Return to REFERENCES or Table 9 Objective To determine optimal variable seeding rates for corn using GIS systems which included soil electrical conductivity measurements elevation and yield potentials A brief partial budget was used to determine the economic feasibility of the combination of these technologies apropos to VRTseeding Methods Using a differential GPS unit soil electroconductivity was used to determine topsoil depth at three different test sites Yield potential seeding rate soil EC and 145 relative elevation data layers were interpolated in 3d map form This information was translated into a grid composed of 457 m blocks to match the harvest width Soil EC was classi ed into ve levels A yield response function regressed EC values to determine seeding rates for each zone VRTseeding rates were compared to uniform seeding rates of 26 000 seedsacre and optimal seeding rates estimated from yield data ResultsConclusion Corn yields and gross returns were higher under the VRTseeding strategy than the URT method across all sites However when application and information costs were considered the net returns from VRT were inferior to the URT seeding strategy The authors suggest that unless better more costeffective soilyield potential diagnostic tools become available VRTseeding using these technology combinations is not currently profitable Crop corn Technology VRTseeding Region Kansas Thompson Wayne H and Pierre C Robert 1995 Evaluation of mapping strategies for variable rate applications Sitespecific management for agricultural systems proceedings from the 2quotd international conference March 2730 Minneapolis MN p 303323 ASNCSSNSSSA Return to REFERENCES or Table 9 Objective Efficacy of two mapping strategies soil survey and grid sample methods were compared as tools used during variable rate application of nitrogen and conventional uniform application of nitrogen Methods Remote sensing images of an llacre plot were digitized and transformed into a contour map indicating field fertility zones and drainage corridors A laser theodolite was used to georeference the plot and to specify elevation variations across the field These data were kriged then loaded into a GIS database Four treatments were a control receiving no nitrogen a conventional nitrogen rate applied uniformly variable N applications based on grid sample kriged results and variable Napplications based on soil survey results Treatments were applied randomly across 16 strips on the experimental plot Each treatment was replicated four times A partial budget evaluated the profitability of the mapping strategies ResultsConclusion There was statistical variability within each of the treatments However there were no appreciable returns from either VRTN mapping strategies when compared to the uniform rate treatment or the control The authors suggest that variable rate technology is not an appropriate management strategy for this particular field Crop corn Technology VRTN mapping Region Minnesota 146 Thrikawala Sunil Alfons Weersink Gary Kachanoski and Glenn Fox 1999 Economic feasibility of variablerate technology for nitrogen on corn American Journal of Agricultural Economics 81 914927 Return to REFERENCES Objective To determine the economic feasibility of variable rate nitrogen application technology to corn Three application strategies are compared VRTN uniform rate and split nitrogen rate applications The authors characterize the additional cost of VRTN and the settlement between efficiency gains from VRTN in View of increased yields and or reduced fertilizer costs Methods A simulation model compared unsubstantiated reports tradeoff between three fertilizer application strategies a constant uniform rate strategy a nonGPS dependent variable rate application strategy where three possible rates are available to the farmer while spraying and a VRT strategy where GPS is used and more than three rates can be applied ResultsConclusion Fertilizer effectiveness increases when the number of management units field variability increases because precise amounts of fertilizer can be determined for specific locations in a field thereby increasing yield and reducing fertilizer input costs When there was a decrease in average fertility an increase in revenues was observed from fertilizer application This relation is not linear and re ects diminishing marginal productivity of the fertilizer term in the yield grain function Fertilizer costs were inversely proportional to soil fertility When soil fertility was either medium to high fertility revenue gains were strongly related to spatial variability This trend was not evident when lowfertility land areas dominated fields As the size of sitespecific management units decreased amounts and costs of fertilizer increased This trend was observed as land fertility variability increased Revenue gains were lowest for uniform application management strategies in medium to high ifertility fields The converse is true for this strategy The authors found that returns from uniform rate applications on predominantly lowfertility fields were superior to VRT since the entire area it applies large amounts of fertilizer to all areas as opposed to VRT On the other hand where there is a mosaic of soil fertility returns from VRT are greater than uniform application strategies Multiplerate VRT suffers losses only when fields were mainly highfertility with little variability VRT identifies specific high productivity areas of a field that can be targeted for higher fertilizer rates thus maximizing the productivity of that area Returns from uniform rate application were generally greater than VRT or split application VRT The authors expected that returns from uniform rate treatments would be greater on more homogenous fields than either VRT treatment they were surprised that returns were greater for uniform rate treatments for variably lowfertility fields For all systems simulated return levels increased as field area increased because fixed costs are distributed over more hectares Environmental benefits accrued from VRT decrease as marginal soil fertility increases because of decreasing marginal productivity of total N related to the assumed fertilizer response function Return to Table 9 Crop corn 147 Technology VRTN Region Ontario Watkins Bradley K Yaochi Lu and Wenyaun Huang 1998 Economic and environmental feasibility of variable rate nitrogen fertilizer application with carryover effects Journal of Agricultural and Resource Economics 232 401426 Return to REFERENCES Objective An EPIC crop growth and a dynamic optimization model were used to study the environmental impacts and profitability of variable rate versus singlerate uniform N application in potato production over the longterm including carryover effects Methods Yields from a 63 ha potato operation were quantified Potato crops were rotated with wheat and barley The authors classified the total yield into four yield groups A dynamic optimization model was used to resolve steadystate N fertilizer levels for each yield group and the field Sixteen N application rates were specified for potato wheat and barley Four application methods were evaluated variable rate and fixed rate both subdivided into preplant applications application during growth Grid sampling was used to determine soil properties The model simulated rotationproduction of these three crops for 30 years Two N application methods were tested preplanting applications and split applications Potato yields and nitratenitrogen carryover concentrations were collected then incorporated into the model ResultsConclusion The total costs of variable rate fertilization 4074ha outweighed the benefits gained from keeping optimal plantN requirements in each yield group Conventional singlerate N application methods 1692ha were more efficient in this context During the potato rotation the split Napplication for both techniques VRT and conventional produced slight returns above the preplant application strategy N losses were not different between conventional and variable rate applications implying that neither method was superior with regards to environmental benefits However N losses to the environment were less under the split application protocol than preplant applications The authors raise several valid points about their findings The model was programmed to simulated yields for seed potato and not N losses Secondly only N availability and soil characteristics were used to explain yield variability while many other factors contribute to yield Thirdly a single field map representing one year was used to estimate soil characteristics throughout the entire simulation The authors recommend using four to five years of field map data Lastly only one input was varied during the simulation N application Profitability of alternative application management methods could be more accurate if additional variables water seeds and pesticides were added to the model RETURN TO INTRODUCTION Crop potato Technology VRTN modeling Region Idaho any 148 Watkins Hal 1999 Additional analysis tools based on yield data Precision agriculture proceedings of the 43911 international conference July 1922 p 1693 ASNCSSNSSSA Return to REFERENCES Objective To offer producers a useful analysis tool to evaluate farms or eld pro tability using yield data Methods Variables such as cash rent input costs costeffectiveness of tillage practices and returns from variable rate technologies are included in an algebraic formula designed to complement GIS data ResultsConclusion Yield was represented as revenue per acre and pro tability by acre The author concludes that better managers would use this type of information to continue farm expansion by rent or lease or to renegotiate other farm loans Crop na Technology record keeping computer use Region na Weiss Michael D 1996 Precision farming and spatial economic analysis research challenges and opportunities American Journal of Agricultural Economics 78 1275 1280 Return to REFERENCES Objective The author asks under what conditions is pro t the net result of precision agriculture activities how does the environment benefit from these practices what level and detail of spatial variability is needed to conduct unsubstantiated reports analyses Methods The author uses personal experience to and supporting sources to de ne the role of spatial economics in the analysis of the economic feasibility of precision agriculture ResultsConclusion Traditional timeseries analyses are not sufficient for analyzing the economic feasibility of precision agriculture Instead analytical tools such as spatial econometric and spatial statistics are needed since factors such as surface f1eld variability time and yield productionareatime must be assigned costs Costs of fertilizer soil testing and application are in uenced as the aforementioned factors vary over time and space The producer practicing precision agriculture is challenged to estimate initially unknown spatial variability deciding where and when fertilizer should be applied to variable regions and at which amounts Identifying variation in soil fertility is largely agronomic while determining fertilizer application rates is economic Crop any Technology precision agriculture general Region any 149 Wibawa Winny D Duduzile L Dludlu Larry J Swenson David G Hopkins and William C Dahnke 1993 Variable fertilizer application based on yield goal soil fertility and soil map unit Journal of Production Agriculture 62 255261 Return to REFERENCES Objective The authors conducted three variable rate application experiments with wheat over three seasons The objectives were to determine whether crop yields and net returns would be augmented using fertilizer recommendations based on soil fertility yield goal and soil maps A conventional uniform application with a fertilizer rate determined by averaging soil test results across the field that was used as a control Methods A field composed of seven soil types was tested for soil fertility Nitrogen phosphorous and potassium test results were used to produce a soil fertility map Samples were taken at five depths at the surface to 48in at 6in intervals Grid sizes were 2500 ftz Soil sampling costs were based on a local dealership custom fee of 3000 for 20 core samples per depth The average field size in North Dakota is 60acres The authors reasoned soil samples for fields this size would cost 050 to 150core when spread out Treatments for one season included 1 no nitrogen application 2 nitrogen and P applications based on averaged soil test results and a yield goal of 80 buacre conventional 3 variable application of nitrogen and P rates based on grid sample results and a 80 buacre yield goal and 4 nitrogen and P rates based on grid sampling and a yield goal determined for each fertility zone Treatments applied other seasons included the above yet slightly modified using larger grid sizes 150 X 150 ft and lower yield goals 50bu acre A partial budget was used to evaluate profitability of treatments ResultsConclusion In 1989 and 1990 Treatment 2 produced the highest net returns of 7314acre 80 buacre and 15642acre 60 buacre respectively In 1991 a treatment including soil test information and soil types and a fertilization rate based on a 50 buacre yield goal produced the largest net return of 11416acre The authors conclude that grid soil sampling provides a good estimate of field fertility variability but resulted in a net loss because of costs An quotinformation approachquot using soil test averaging these results and making fertilizer rate recommendations based on this average had the best results Return to Table 9 Crop wheat Technology VRT grid sampling Region North Dakota Wollenhaupt NC and DD Buchholz 1993 Profitability of farming by soils In Site specific management for agricultural systems p 199211 ASNCSSNSSSN Madison WI Return to REFERENCES 150 Objective The authors summarize the results of four eld trials that investigated the marginal returns of variable rate application Methods The variable costs associated with grid and soil sampling tests map making fertilizer costs and application data management costs and labor costs are given Two soil analysis techniques are compared soil potential and nutrient grid techniques Information each technique provided was used to generate soil maps From these maps fertilizer recommendation rates were made Crop yields were compared between treatments along with a yield return minus cost analysis ResultsConclusion Sitespecifrc soil management techniques were not profitable compared to conventional soil fertility management techniques Special application equipment additional soil sampling and analysis data management and map making incurred higher costs of the sitespecific management strategy Variable rate applications did not decrease yields when compared to conventional application strategies The study raises the question as to what appropriate sample spacings are optimal for yield and profit Crop wheat Technology VRT Region Montana Minnesota Missouri Wollenhaupt Nyle C Richard P Wiolkowski and Harold F Reetz 1993 Variable rate fertilizer application update and economics Unpublished document University of WisconsinMadison Potash and Phosphate Institute Monticello Ill Return to REFERENCES Objective To summarize findings of an ongoing study examining soiltesting strategies grid sampling methods and soil fertility zone contour mapping and the economic feasibility of making variable rate fertilizer application recommendation using these techniques Methods Two corn production fields were used as study sites Gridpoint and gridcell sampling methods strategies were used to obtain soil nutrient information Five core samples were collected in each grid Grid sizes tested in the gridpoint method were 106 X 106 212 X 212 or 318 X 318ft Grid sizes in the gridcell sizes were 318 X 318ft In this treatment soil sample results were either averaged using five sample points treatment A or considered representative for that grid using 72 sample points treatment B Samples were taken at the intersection of each grid for the former method In the gridcell method samples were taken along the diagonal of each grid Four mapping techniques were compared 1 inverse distance weighting 2 fitting regression functions to field data followed by inverse distance weighting 3 point kriging and 4 block kriging The authors assumed a 250 buacre corn price and phosphorous and potassium fertilizer prices to be 025 and 012lb respectively Fertilizer rate 151 recommendations were made using the results of each method Fertilizer was applied according to each recommendation ResultsConclusion Comparing results between both eld the only treatment generating positive net returns was the gridpoint sampling method with a 318 x 318ft spacing Results from the other methods between eld were mixed The authors conclude that although these methods certainly provide useful information about soil fertility zones singlerate application methods are still more costeffective than variable rate techniques However the information provided by soil testing gives the producer a more exact idea how much fertilizer to apply to a specific field than to rather rely on general extension information Return to Table 9 Crop corn Technology VRT grid sampling Region Wisconsin Wollenhaupt NC and RP Wolkowski 1994 Grid soil sampling for precision and profit Unpublished manuscript Department of Soil Science University of Wisconsin Madison WI Modified from a paper prepared for the 24Lh North Central Extension Industry Soil Fertility Workshop St Louis MO October 2627 1994 Return to REFERENCES Objective To provide a detailed methodology of grid sampling and to determine economically optimal grid dimensions for sitespecific fertilizer recommendations A detailed list of procedural costs is included Methods The authors provide a stepbystep list how soil testing by grid sampling is accomplished Hypothetical grids of varying dimensions were chosen Then a breakdown of the associated costs labor data analysis and laboratory tests by acre is outlined Using yield and inputoutput cost data from five different farms the authors produce a partial budget To estimate yield response functions were adjusted to real crop and fertilizer prices Simulated results were used in the partial budget analysis ResultsConclusion Sampling density in uenced mapping accuracy The degree of precision and soil sampling costs has to be considered when determining sampling density In three fields dense soil sampling revealed that although there was much variability readings were such that no fertilizer was needed since the field soil was high quality Soil and pH tests were low for the remaining two fields Problem areas required further testing to accurately pinpoint fertilitypoor zones Economic returns were mixed The authors conclude that field history should be a guide as to whether or not grid sampling is needed If indicators suggest that grid sampling might remedy fertilitypoor soils then again field history should be consulted Soil sampling may require more than one trip to a field in order to finetune recommendations Crop corn 152 Technology grid sampling VRT Region Wisconsin Yadav Satya N 1997 Dynamic optimization of nitrogen use when groundwater contamination is internalized at the stande in the long run American Journal of Agricultural Economics 79 931945 Return to REFERENCES Objective The objective of this study was to determine optimal N input levels for continuous corn production keeping N loading into groundwater less than 10 ppm Experimental data was used to produce policy relevant information after it served as the raw material for a dynamic optimization model The objective of the model was to stabilize nitrogen load in the groundwater over time The model included a social bene t function Results were compared with extant policy regulating nitrogen contamination rates in groundwater Methods The author combines three years of production data from three different sites and different combinations of treatments including use of inorganic or organic N N application timing application method and tillage practices The experiment was a randomized block design with a total of 608 data points Soilwater samples from each site were collected from a depth of eight feet Samples from groundwater sources were not available Three different dynamic optimization models were borrowed then adapted to make the model used in this report The resulting model included a social benefit function to measure what effects an increase or decrease in nitrogen use would have on society as extemalities and private profit the farm firm ResultsConclusion Years and treatments varied significantly across sites Within sites there no differences between treatments were observed From the model results farmers in this region are using substantially more N fertilizer than recommended by extension agents and more than is necessary to maximize profits Furthermore the model indicates that it is more prudent to apply nitrogen based on specific site needs than one general application rate for the entire region based on current extension recommendations In the three study sites nitrogen application rates exceeded profitmaximizing levels In addition recognizing carryover effects from N applications from previous years the author foresees N rate recommendations decreasing It follows that farmers could lower production costs and the propensity to contaminate groundwater sources with N fertilizers would diminish Crop corn Technology VRTN Region Minnesota Yule IJ PJ Cain EJ Evans and C Venus 1995 A spatial inventory approach to farm planning Computers and electronics in agriculture 14 151161 Return to REFERENCES 153 Objective The authors provide a synopsis of the components of precision agriculture A brief description of each is provided A system to meet the requirements necessary for planning precision agriculture activities along with nancial management strategies is provided The authors offer a partial budget covering barley and variable rate fertilizer application Methods System requirements of precision agriculture are listed then elaborated The authors mention the use of yield and soil maps and data pertaining to annual weed distribution topography hydrology soilsampling methods and data acquisition and storage A cursory unsubstantiated reports analysis is provided as an example of determining the pro tability of these technologies Using an average annual application rate of l60kg Nha with a cost of 30 pencekg it costs 4800ha to grow barley Barley market price was assumed to be 10000tonne A yield function is used to determine the economic feasibility of variably applied nitrogen An optimum grain to nitrogen response was assumed to be a ratio of3l ResultsConclusion The authors suggest that sitespecific management should permit the economically optimal application to specific management zones in a field as opposed to uniform blanket application methods It follows that the smaller the management unit the greater chance an optimal fertilizer saturation point will be achieved The effect variable rate application has on profitability depends upon the degree of spatial fertility variability within the field in comparison to returns form conventional uniform application rates The authors assume a 6 interest rate with a machinery amortization period of 8 years With annual returns of 1100ha using VRT an additional 6800 of capital costs could be supported The authors estimate a breakeven investment level of 1360000 on 200ha Including other costs such as GPSmodifred equipment variable rate spreaders and data management systems at package rate of 2000000 a producer would have to farm a minimum of 295ha to make VRT a profitable venture Crop barley Technology VRT Region England 154 INSTANT SLUSH Bette A Bridges Bridgewater Raynham Regional High School 166 Mt Prospect St Bridgewater MA 02067 bbrid es brid e ra or 5086976902 x268 Chemical Concepts 0 partial pressure 0 gas solubility o Henry s Law 0 colligative propertiesifreezing point depression Discussion The solubility of carbon dioxide in water is dependent upon the temperature the partial pressure of C02 above the liquid and the pH of the water The production of carbonated drinks involves the dissolving of C02 at low temperature and high pressure resulting in a saturated solution Soda water is bottled under high pressure in order to maintain the level of dissolved C02 When a bottle of soda is rst opened one can hear the familiar sssssst due to the escaping C02 This lowers the partial pressure of the C02 above the liquid which lowers the solubility of the C02 in the liquid Henry s Law The excess C02 solute begins to come out ofthe solution gas bubbles are visible When a sealed bottle of soda is covered in ice the liquid inside does not freeze due to the dissolved substances in the liquid including the C02 The freezing point of a liquid solvent is lowered when a solute is dissolved in it The greater the amount of dissolved solute the lower the freezing point of the solution The chemical nature of the solute does not in uence the degree the freezing point is lowered only the total numbers of solute particles present per kg of solvent colligative properties A sealed bottle of soda usually will not freeze above 10 C In this demonstration a sealed bottle of soda water is chilled in an icesalt mixture to a temperature around 8 C The bottle is then removed and the cap is loosened The familiar ssssst is heard bubbles of escaping C02 can be seen leaving the liquid and the liquid begins freezing from the top and continues downward until nearly all of the liquid is frozen This phenomenon can be explained at least partially through our knowledge of colligative properties When the C02 escapes from the liquid after the cap is loosened the concentration of the remaining solution is lowered fewer particles dissolved per kg The lower concentration results in less of a freezing point depressionithe solution will freeze at a higher temperature The liquid begins to freeze when the concentration is lowered suffrciently so that the temperature is now below the freezing point of the mixture NOTE There has been a significant amount of discussion concerning the explanation of this phenomenon It has been argued that the concept of freezing point depression does not fully explain what occurs Materials 0 lZoz or l6oz glass bottle of soda water remove the label 0 Icesalt or iceacetone bath 0 Thermometer optional Safety 0 The temperature of the icesalt bath may drop sufficiently to freeze the liquid in the bottle of soda The bottle may break due to the expansion of the water as it freezes It is recommended that one keep an eye on the temperature using a thermometer Wear protective leather gloves and safety goggles If using an iceacetone bath be sure there is adequate ventilation Do not dispose of acetone in the sink Procedure 0 Let an unopened glass bottle of soda seltzer water cool completely surrounded by an ice salt or ice acetone bath until thermal equilibrium about 20 minutes is reached Carefully lift the bottle partially out of the bath and show the students that the soda is still completely liquid 0 Break the seal to open the bottle Be sure the students view of the bottle is not obstructed 0 Slowly lift the bottle out of the bath allowing students to see the freezing of the liquid NOTE If small glass bottles of soda water are not available in your area small bottles of PerrierTM water work well although they are more expensive Club soda tends to work best Pedagogical Applications 1 Prepare in advance the salt ice bath with the bottle of soda water Also prepare a second ice only bath with a bottle of soda water Have a third bottle of soda which is at room temperature 2 Hold up the room temperature bottle of soda water and ask the students what they would observe see and hear when the lid is loosened Enter into a discussion as to why the dissolved gas comes out of solution and the effect on the concentration of the remaining solution Review Henry s Law 3 Show the students the bottle of soda water that is in the ice only bath Let them see that the temperature is around 0 C yet the solution inside the bottle is not frozen Enter into a discussion as to why the solution has not yet begun to freeze Be sure the ideas associated with colligative properties freezing point depression and the effect changing the concentration has on the freezing point Finally get 4 0 the students to suggest ways to get the solution to freeze lower the temperature andor lower the concentration Show the students the third bottle of soda that is in the icesalt bath Let them see the temperature is now well below 0 C and that the liquid inside is still not frozen hopefully Let them explain why it is still not frozen Then ask the students what will happen when the cap is loosened Allow for all possible predictions Get the students to offer explanations for their predictions Perform the demonstration Follow up discussion should center on what happened and why Get students to verbalize the explanation for the phenomenon Be sure students who offered alternative predictions are involved in explaining what actually happened
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