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CH. 4 First Part

by: Payton Gilmore

CH. 4 First Part PSS 3303

Payton Gilmore
GPA 3.8

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About this Document

Will be on exam (part was on previous exam)
Dr. Jac J. Varco
Class Notes
soils, Soil Science
25 ?




Popular in Soils

Popular in plant and soil sciences

This 4 page Class Notes was uploaded by Payton Gilmore on Tuesday October 4, 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 3 views. For similar materials see Soils in plant and soil sciences at Mississippi State University.

Similar to PSS 3303 at MSU

Popular in plant and soil sciences


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Date Created: 10/04/16
CH. 4 PHYSICAL PROPERTIES:  Soil Productivity  Water holding capacity and drainage  Construction suitability SOIL TEXTURE:  Fine earth fraction, excludes pebbles, rocks, etc.  The diameter of a particle determines which of the soil separates it is. The USDA classification is as follows: FIG. 4.1, PG. 98 IN BOOK  Soils are approximately 45% by volume mineral matter. Relative proportions of sand, silt, and clay (soil separates) comprise or determine the texture of a soil. SEE FIG. 4.2, PG. 99  Decreasing particle sizeSurface area increases.  Adsorption of water, gases, and nutrients and a greater attraction of particles to each other greater. (also faster weather, ^ swelling, plasticity, and cohesion)  Sand and Silt Particles don’t stick together  FIG. 4.3 PG. 99 SOIL TEXTURE GENERALIZATIONS:  Clay Soils o Hold > H2O than coarser textures o Hold > nutrients than silt and sand o Adsorb > gases such as NH3 o Develop > structure  Sandy Soils o > permeability to air and water o Lower water and nutrients o Lower in organic matter o Less developed structure SOIL TEXTURE TRIANGLE- 12 TEXTURAL CLASSES  SEE FIG. 4.4, PG. 101  Loam best soils to garden o Less clay  Soybeans are grown on clay  Cotton- silt loam SOIL STRUCTURE  Arrangement of individual soil particles into larger units.  Units of soil structure- peds or aggregates; natural groups of soil separates, occur and persist within the soil o Many soils in the Delta have lost OM and SS is down CLASSIFICATION OF SOIL STRUCTURE A. Grade 1. Weak- aggregates too weak to remain intact upon removal 2. Moderate- remain intact when removed from soil, but can be crushed 3. Strong- visible in undisturbed soil, break into whole peds when removed from profile. Difficutly in crushing. 4. Structure-less- no observable aggregation, no natural planes of weakness. - Single grain in non-coherent 2 - Massive if coherent- commonly found in C horizons/parent material B.Class o Size of ped or aggregate a. Fine b. Medium c. Coarse C.Type o Shape of peds, natural planes of weakness 1. Spehrical- round in shape - Granular: porous - Crumb: very pourous o Good aeration, drainage, and highly desirable for plant growth. A horizons especially under grassland conditions. 2. Platy-peds with greater horizontal dimensions than vertical - Usually found in A  E horizons. Related to parent material, frost action, water table fluctuations, and horizontal water movement. 3. Prism-like- dimensions greater in the vertical than horizontal - Prismatic: square tops - Columnar: rounded tops o B horizons well-developed soils. Most common in aridisols. Fragipans of MS. 4. Block-like- equal size in 3D - Angular blocky - Subangular blocky 3 o Common in B horizons - Ex. Strong, medium, subangular blocky  Fig. 4.8, pg. 106 GENESIS OF SOIL STRUCTURE 1. Physical processes-orientation of soil particles - Wetting and drying - Freezing and thawing - Root action - Action of soil organisms - Textural influences 2. Biological - Plant root exudates - Microbial by-products - earthworm activity To learn more and get OneNote, visit 4


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