A Word About

Soil Texture

Soil texture is a useful classification of soil and is based on its content of sand, silt and clay. At one extreme we have pure sand, and at the other, pure clay. Most soils are mixtures that fall between these extremes.

Soil texture is the distribution of particle sizes in soils, which dictates the differentiation of soil texture by classes.

Many definitions of sand and silt exist. In all major soil texture systems clay is defined as being less than 2µm in size, but for silt and sand various size limits exist. Since silt and sand sizes overlap in different systems (and countries, all thinking theirs is the best) no definite soil texture classes can be assigned on a worldwide basis.

Some systems contain the texture class "loam" which is generally considered an optimum texture. Most systems do not contain "loam" as a single soil texture, but rather a combination like "sandy loam" or "silt loam." In these, perhaps the "clay loam" is an optimum class, but it probably is too broad a classification.

If we want to define optimum texture, the best definition we can use is more or less even distribution of soil particle sizes of <2mm, somewhat bias to the middle ranges (2µm-200µm).