This article includes alist of references,related reading, orexternal links,but its sources remain unclear because it lacksinline citations. Please helpimprove this article byintroducing more precise citations.(June 2022) (Learn how and when to remove this message)

Subsoil is the layer of soil under thetopsoil on the surface of the ground. Like topsoil, it is composed of a variable mixture of small particles such assand,silt andclay, but with a much lower percentage oforganic matter andhumus. The subsoil is labeled theB Horizon in mostsoil mapping systems. Because it has less organic matter thantopsoil, subsoilsoil colour is mainly derived from iron oxides. Iron oxides and clay minerals form due toweathering. Rainfall moves these weathering products downward assolutes andcolloids by rainfall. The subsoil is the depth where these weathering products accumulate. The accumulation of clay minerals, iron, aluminum, and organic compounds is calledilluviation.

Whereas the topsoil tends to be the depth of greatest physical, chemical, and biological activity, the subsoil is the depth of most deposition. Due to physical, chemical, and biological activity, the subsoil generally has asoil structure. The presence of structure distinguishes the subsoil from the underlying substratum. Due to human activity, the topsoil and subsoil in many environments have been mixed. Below the subsoil is the soil substratum (or C horizon).

Clay-based subsoil has been the primary source ofmaterial foradobe,cob,rammed earth,wattle and daub, and other earthen construction methods for millennia. Coarsesand, the other ingredient in most of these materials, is also found in subsoil.

Although not sterile, subsoil is relatively barren in terms ofsoil organisms compared to humus-rich topsoil.

• Soil
• Soil horizon
• Subgrade
• Parent rock

• Håkansson, Inge; Reeder, Randall C. (March 1994). "Subsoil compaction by vehicles with high axle load—extent, persistence and crop response".Soil and Tillage Research.29 (2–3):277–304.doi:10.1016/0167-1987(94)90065-5.(subscription required)
• Adams, Fred; . Moore, B. L (January 1983)."Chemical Factors Affecting Root Growth in Subsoil Horizons of Coastal Plain Soils".Vol. 47 No. 1. Soil Science Society of America Journal. pp. 99–102. RetrievedOctober 11, 2012.(subscription required)

Thishorticulture article is astub. You can help Wikipedia byexpanding it.

• v
• t
• e

• Types of soil
• Horticulture stubs

• Articles with short description
• Short description matches Wikidata
• Articles lacking in-text citations from June 2022
• All articles lacking in-text citations
• Pages containing links to subscription-only content
• All stub articles