Clay soil

Clay Soil
Soil material containing more than 40 percent clay, less than 45 percent sand, and less than 40 percent silt.
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clay soil. A soil containing more than 40 percent clay, but less than 45 percent sand, and less than 40 percent silt.

Coarser textured soils, such as sands, have a higher percentage of non-capillary pores so they drain easily and do not retain as much water as a clay soil.

cap : A fairly impermeable seal, usually composed of clay-type soil or a combination of clay soil and synthetic liner, which is placed over a landfill during closure.

See also: Mining, Well, Organic, Toxic, Compounds