- Gley soil
Gley soil in
soil science is a type ofhydric soil which exhibits a greenish-blue-greysoil color due towetland conditions. On exposure to the air, gley colors are transformed to a mottled pattern of reddish, yellow or orange patches. During gley soil formation (a process known as Gleying), theoxygen supply in thesoil profile is restricted due tosoil moisture at saturation. Anaerobic micro-organisms supportcellular respiration by using alternatives to free oxygen as electron acceptors. This is most often the case when thesesquioxide ofiron ,ferric oxide isreduced toferrous oxide by the removal of oxygen. These reduced mineral compounds produce the gley soil color.Gley soils may be sticky and hard to work, especially where the gleying is caused by surface water, held up on a slowly permeable layer. However, some
ground-water gley soils have permeable lower horizons, including some sands, for example in hollows within sand dune systems, known as slacks, and in somealluvial situations.Groundwater gley soils develop where
drainage is poor because thewater table (phreatic surface) is high, whilst Surface-water gleying occurs when precipitation inputs at the surface do not drain freely through the ground. A reducing environment exists in the saturated layers, which become mottled greyish-blue or brown because of the content offerrous iron and organic matter. The presence of reddish or orange mottles indicates localised re-oxidation of ferrous salts in the soil matrix, and is often associated with root channels, animal burrows or cracking of the soil material during dry spells.Most
soil classification s divide the gley soils into surface-water gleys (also known asstagnogleys ) and gleys proper, or groundwater gleys, the former having a slowly pemeable lower subsoil, leading to a "perched" water table, the latter being in low ground or basin situations where the natural groundwater table is constantly high enough to influence the soil profile.It is also a cheap alternative to clay.
ee also
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Anaerobic respiration
*Redox
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