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Soil texture, or how the soil looks and feels, is determined by the size and proportion of the particles (clay, silt, and sand) that make up the mineral fraction. There are 12 USDA textural classes (e.g., sandy loam, silty clay). Significance:
The textural class of a soil is its most fundamental inherent characteristic that changes little over time (van Es et al., 2016). Its role in soil health studies is to inform the interpretation of most of the soil health indicators. Numerous soil properties are influenced by texture, including drainage, water-holding capacity, water movement through soil, infiltration, susceptibility to erosion, organic matter content, cation-exchange capacity, pH buffering capacity, and aeration. Soil texture also influences soil fertility, root growth, and plant vigor.
Factors Affecting Soil Surface Texture:
Inherent factors.—The nature and composition of the soil parent material greatly influences the particle-size distribution, or texture. Weathering of rocks and soil materials also affect the soil texture. Clays typically form over long periods of time through gradual chemical weathering. Freeze-thaw action can break apart rocks and gradually reduce the particle size of soil materials over time. Translocation of soil particles (e.g., clay) within the profile and between layers can alter the soil texture. Additions of particles by wind or water also affect the soil texture.
Dynamic factors.—Soil texture is altered little by management practices if the soil remains in place. Accelerated erosion by wind or water can remove the topsoil, exposing a subsoil with a different texture. Deposition of eroded materials can alter the texture of the surface soil. Deposition can be natural or anthropogenic (due to human activity). Land leveling and alteration (e.g., terracing) can change the soil texture.
Measurement:
The feel method is a crude method by which one can broadly judge the classes of soil texture. The lab methods involve removal of organic matter from a soil sample, the dispersion of the soil sample into single particles, and then the separation of sand through sieving. Clay is determined through sedimentation based on Stoke’s law. The full procedure is described in the Kellogg Soil Survey Laboratory Methods Manual (Soil Survey Staff, 2014).
References:
Soil Survey Staff. 2014. Kellogg Soil Survey Laboratory methods manual. Soil Survey Investigations Report No. 42, Version 5.0. R. Burt and Soil Survey Staff (eds.). U.S. Department of Agriculture, Natural Resources Conservation Service.
van Es, H., R. Schindelbeck, A. Ristow, K. Kurtz, and L. Fennell. 2016. Soil texture. Soil Health Manual Series. Fact Sheet No. 16-04. School of Integrative Plant Sciences, Cornell University, NY.
Aggregation Method: Dominant Condition; Tiebreak rule: Lower
Top horizon depth: 0; Bottom horizon depth: 1
Component Percent Cutoff: 0%
GeoDatabase: C:\Users\nina.mauney\Desktop\AACD\BigSandy_NRCD\Data\soils_GSSURGO_az_3816689_01\soils\gssurgo_g_az\gSSURGO_AZ.gdb
Featurelayer: MUPOLYGON
Rating Table: SDV_TexSurf_DCD_0to1
Layer File: C:\Users\nina.mauney\Desktop\AACD\BigSandy_NRCD\Data\soils_GSSURGO_az_3816689_01\soils\gssurgo_g_az\Soil_Health_-_Surface_Texture_DCD_0_to_1cm.lyr |