Subsoil

subsoil, the usually heavier-textured layer of a soil profile which underlies the main zone containing roots and organic matter. It overlies the bedrock (See rock) or sediments from which the soil is formed. The contrast in texture between surface soil and subsoil is greatest in ancient soils and in forest (especially pine forest) regions, due to the progressive downward leaching of the heavier minerals and fine clay particles. Such subsoils are, however, typically depleted of many of the important nutrient elements, because roots have continuously extracted them from depth and deposited them at the surface in leaf litter and derived organic matter.