View source for Subsoil

{{Short description|Layer of soil under the topsoil on the surface of the ground}}
{{distinguish|Substrata (disambiguation){{!}}Substratum}}
{{No footnotes|date=June 2022}}
[[File:Devon Culm Subsoil - geograph.org.uk - 344702.jpg|thumb|Subsoil layer]]
'''Subsoil''' is the layer of soil under the [[topsoil]] on the surface of the ground. Like topsoil, it is composed of a variable mixture of small particles such as [[sand]], [[silt]] and [[clay]], but with a much lower percentage of [[organic matter]] and [[humus]].  The subsoil is labeled the [[soil horizon|B Horizon]] in most [[soil mapping]] systems. Because it has less organic matter than [[topsoil]], subsoil [[soil color|soil colour]] is mainly derived from iron oxides. Iron oxides and clay minerals form due to [[soil formation|weathering]]. Rainfall moves these weathering products downward as [[solutes]] and [[colloids]] by rainfall. The subsoil is the depth where these weathering products accumulate. The accumulation of clay minerals, iron, aluminum, and organic compounds is called [[illuviation]].

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 a [[soil 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 of [[material]] for [[adobe]], [[cob (material)|cob]], [[rammed earth]], [[wattle and daub]], and other earthen construction methods for millennia. Coarse [[sand]], the other ingredient in most of these materials, is also found in subsoil.

Although not sterile, subsoil is relatively barren in terms of [[soil organisms]] compared to humus-rich topsoil.

==See also==
{{portal|Ecology}}
* [[Soil]]
* [[Soil horizon]]
* [[Subgrade]]
* [[Parent rock]]

==Sources==
* {{cite journal | title=Subsoil compaction by vehicles with high axle load—extent, persistence and crop response | journal=Soil and Tillage Research | volume= 29|issue= 2–3 | date=March 1994 |author1=Håkansson, Inge |author2=Reeder, Randall C. | pages=277–304 | doi=10.1016/0167-1987(94)90065-5}} {{Subscription required}}
* {{cite web |url=https://www.crops.org/publications/sssaj/abstracts/47/1/SS0470010099 | title=Chemical Factors Affecting Root Growth in Subsoil Horizons of Coastal Plain Soils | work=Vol. 47 No. 1 | publisher=Soil Science Society of America Journal | date=January 1983 | access-date=October 11, 2012 |author1=Adams, Fred |author2=. Moore, B. L | pages=99–102}} {{Subscription required}}

{{Geotechnical engineering}}{{Soil type}}{{Authority control}}

[[Category:Types of soil]]


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