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Field Assessment

Soil texture is determined in the laboratory through particle size analysis or manual texturing (Figure 3.1.5). Based on the proportions of mineral content in a soil, the soil textural triangle is used to determine a soil’s textural class (Figure 3.1.4). For example, clay dominated soils are defined as fine textured, while sand dominated soils are coarse textured.

Adapted from Glossary of Soil Science Terms, 1976

Figure 3.1.4 The Soil Textural Triangle

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Before applying manure to a field, AOPA requires a one-time laboratory test to determine soil texture. Details on AOPA soil testing requirements for nutrient management are discussed in Chapter 3.3.

Determining Soil Texture Using the Soil Textural Triangle

The particle size separation of three samples yielded the following percentages of sand and clay: Sample % Sand % Clay A 18 20 B 2 36 C 35 27

Based on Figure 3.1.4, sample A is a silt loam, B is a silty clay loam, and C is a loam.