(also called substrata
) is the layer of soil
under the topsoil
on the surface of the ground. The subsoil may include substances such as clay
and has only been partially broken down by air
etc., to produce true soil. Below the subsoil is the substratum, which can be residual bedrock
, sediments, or aeolian deposits, largely unaffected by soil-forming factors active in the subsoil. It contains partially weathered particles.