Subsoil

Definition

Subsoil is the layer beneath the topsoil, usually lighter in colour, lower in organic matter and denser. It stores water and nutrients and is where deep roots reach, but it is far less fertile and holds fewer living organisms. When erosion strips the topsoil, pale subsoil may show through on knolls and slopes, which is a common warning sign. Subsoil can also be compacted by heavy machinery, a problem that is hard to repair. See also: Topsoil, Soil horizon, Compaction, and the guide "Soil Compaction and the Loss of Soil Structure".