Ch. 6 Soils Notes
Ch. 6 Soils Notes PSS 3303
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This 5 page Class Notes was uploaded by Payton Gilmore on Monday October 3, 2016. The Class Notes belongs to PSS 3303 at Mississippi State University taught by Dr. Jac J. Varco in Fall 2016. Since its upload, it has received 12 views. For similar materials see Soils in plant and soil sciences at Mississippi State University.
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Date Created: 10/03/16
Chapter 6 Soil and the Hydrologic Cycle Hydrologic Cycle Water movement within the Soil-Plant-Root System - Image (on slides) - Diagram (on slides) Soil water usage and loss Evapotranspiration- Evaporation of water from soil- transpiration of water from plants - Bare soil evaporative losses are high - Closed plant canopy transpiration losses are high Roots grow deeper and horizontally Weeds Pan evaporation- evaporation from standing or ponded water. July to August- 0.2 to 0.3 inch/day The deeper the soil dries, the slower the evaporation becomes Diagram (on slides) Evaporation rate vs Time Sandy soils can be considered self-mulching Silty soils- high capillarity, dust mulch breaks capillaries Image (on slides) cracking soils H2O vapor When soils begin to crack more water and H2O vapor can escape Leaf area index image Row crops- soil evaporation high early in season, transpiration greater as crop canopy develops Forest vegetation- soil evaporation low (transpiration high) due to canopy cover, forest litter, and low wind - Pine trees can loose water year round - While Oak trees (Deciduous forest) have no where to loose water from in the winter Grassland- evaporation and transpiration can be high Image Corn and Deciduous forest ** will question on this Environmental effects on evaporation-transpiration 1. Temperature (increase evaporation) 2. Humidity (decrease evaporation) 3. Canopy cover 4. Wind speed 2. Infiltration/Percolation-movement into, within, and through a soil profile, macropore flow, movement to groundwater or surface waters. - K-sat.- A hor. C 3. Runoff- rainfall rate exceeds infiltration rate. Urban effects on runoff. Soil recharge Replenishment of micropore water throughout the rooting zone Depends on: - Soil texture - Structure /PSD - Slope - Infiltration/percolation rates - Surface roughness - Mulch or surface residues 2 Soil wetting patterns - Sandy vs. clayey - Coarse texture below fine Image (on slides) Water Supplying Capacity (WSC) Capacity off a soil to supply plants during a period of rainfall deficit. Available Water In/Ft Coarse sand 0.75 Sandy loam 1.30 Loams and Silt Loams 2 to 3 Clay loam and clays 2 Total available water depends on: - Texture PSD - Organic matter content - Effective rooting depth or volume o Chemical barriers such as acid pH o Physical barriers a. Water table ~ capillary fringe b. Hardpan/fragipan c. Soil depth Fig 6.9 pg. .172 Soil Water Management Image: water battles Factors which can improve soil water management: 3 1. Mulching- reduce evaporation rate, maintain soil OM, structure, and high infiltration rates, prevents crusting and slows run off. (NT production vs. conventional tillage) 2. Weed control 3. Maintain organic matter- Improves structure and porosity. High water holding capacity-availability similar to clay. 4. Terraces- slow runoff and reduce erosion q 5. Deep tillage- destroy tillage hard pan. Increase infiltration during rainy season. 6. Fallow land- used in drier areas to store soil moisture. Great Plains, ND, SD, MT, CO, KS, and TX. 7. Optimize fertility- crops grow more efficiently, thus increasing water-use-efficiency 8. Irrigation- use of wastewater, sprinkler, center pivot, traveling gun, furrow, or flood irrigation, and trickle or drip - (rice-intermittent flood, land forming, catfish) Managing too much water Current wetland conservation prevents drainage Dikes, levees, and canals are already in use Fields already have ditches or drain tiles Bedding soil improves drainage - Hipping Benefits of drainage include: - Increased aeration - Increased rooting depth - Timeliness 4 - Faster soil warming (temperature) 5
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