Naturally occurring salts, chemical fertilizers, and pesticides are subject to leaching. Whether leaching actually occurs depends on the amount of water passing through the soil and the rate of water movement. Leaching potential refers to the risk that soluble pesticides will be transmitted through the soil to the groundwater reservoir. Leaching potential depends on soil permeability, water table conditions, and hydraulic loading. Permeability refers to the rate at which water moves through soil.
Permeability is controlled by the size and continuity of the soil pores.
Unbalanced mixtures dominated by increasing amounts of sand are called sandy loam, loamy sand, and just plain sand. If clay dominates, the texture is called clay loam, or, with more clay, just plain clay. Silty soils that contain little or no sand are called, in order of increasing clay content, silt loams, silty clay loams, or silty clays. Coarse-textured sandy and gravelly soils have the largest pores and the most rapid permeabilities. Fine-textured clayey soils have very tiny pores and very slow permeability rates.