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Soil texture refers to the size distribution of mineral particles in a soil. Sand (rated from coarse to very fine), silt and clay refer to textures of decreasing particle coarseness. Soils with a high proportion of sand have very limited storage capacity for water, whereas clays are excellent in retaining water. One soil identification system has defined eleven soil types on the basis of their respective proportions of clay, silt and sand. The eleven types are:
Sand
Loamy sand
Sandy loam
Sandy clay loam
Clay loam
Loam
Silty loam
Silt
Silty clay loam
Silt clay and clay
Another identification scheme has utilized chemical composition, organic content and history of formation to define types such as gravel, humus, marsh and peat.
A newer soil classification system has evolved in the USA that can be utilized to classify soils globally, at any location. In this "universal" classification system soils are considered as individual three- dimensional entities that can be grouped according to similar physical, chemical and mineralogical properties. The system uses a hierarchical approach, with the amount of information about a soil increasing down the classification ladder.
