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Gleysol
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<p>A gleysol or gley soil is a <a href="/facts/Hydric_soil/dxaNEKrV">hydric soil</a> that unless drained is saturated with <a href="/facts/Groundwater/JYM2IDS2">groundwater</a> for long enough to develop a characteristic gleyic colour pattern. The pattern is essentially made up of reddish, brownish, or yellowish colours at surfaces of <a href="/facts/Ped/TQXHGIXo">soil particles</a> and/or in the upper <a href="/facts/Soil_horizon/GcXhdams">soil horizons</a> mixed with greyish/blueish colours inside the peds and/or deeper in the soil. Gleysols are also known as <i>Gleyzems</i>, <i>meadow soils</i>, <i>Aqu</i>-suborders of <a href="/facts/Entisols/M3YXey2N">Entisols</a>, <a href="/facts/Inceptisols/Tt89IvaM">Inceptisols</a> and <a href="/facts/Mollisols/lxyTVyAR">Mollisols</a> (<a href="/facts/USDA_soil_taxonomy/HgpyDsEX">USDA soil taxonomy</a>), or as <i>groundwater soils</i> and <i>hydro-morphic soils</i>. </p><p>The term gley, or glei, is derived from <a href="/facts/Ukrainian_language/2zDw7rpD">Ukrainian</a>: глей, <a href="/facts/Romanization_of_Ukrainian/GYvveb1q">romanized</a>: <i>hlei</i>, and was introduced into scientific terminology in 1905 by the <a href="/facts/Ukraine/Qof0uqAj">Ukrainian</a> scientist <a href="/facts/Georgy_Vysotsky/FRcMI4VR">Georgy Vysotsky</a>. </p> <p>Gleysols occur within a wide range of <a href="/facts/Compaction_(geology)/Pv3ntyLR">unconsolidated materials</a>, mainly <a href="/facts/Fluvial/nkLrSheo">fluvial</a>, <a href="/facts/Marine_(ocean)/8W8lYgjD">marine</a> and <a href="/facts/Lake/YP0xxn0E">lacustrine</a> <a href="/facts/Sediment/zsIH1A6U">sediments</a> of <a href="/facts/Pleistocene/0ya9eUp5">Pleistocene</a> or <a href="/facts/Holocene/sppPgwW5">Holocene</a> age, having <a href="/facts/Base_(chemistry)/M9wA7qeM">basic</a> to <a href="/facts/Acid/FySU18n1">acidic</a> <a href="/facts/Mineralogy/MeIK9lx9">mineralogy</a>. They are found in <a href="/facts/Depression_(geology)/HhqyUdz5">depression</a> areas and low <a href="/facts/Landscape/pU9HneR0">landscape</a> positions with shallow groundwater. </p><p>Wetness is the main limitation on agriculture of virgin gleysols; these are covered with natural <a href="/facts/Swamp/rjE9QKpm">swamp</a> <a href="/facts/Vegetation/nAHr9kjk">vegetation</a> and lie idle or are used for extensive <a href="/facts/Grazing/nxF45P2c">grazing</a>. Farmers use artificially-drained gleysols for <a href="/facts/Agriculture/TGztqzJs">arable cropping</a>, <a href="/facts/Dairy_farming/qBY8ItMr">dairy farming</a> and <a href="/facts/Horticulture/m8qBLuT3">horticulture</a>. Gleysols in the <a href="/facts/Tropics/Iv1es8Ih">tropics</a> and <a href="/facts/Subtropics/gK0KyFUD">subtropics</a> are widely planted with <a href="/facts/Rice/wvL1hBCz">rice</a>. </p><p>Gleysols occupy an estimated 720 million hectares worldwide. They are <a href="/facts/1938_USDA_soil_taxonomy/vK9VlB10">azonal soils</a> and occur in nearly all <a href="/facts/Climate/f57XrNFU">climates</a>. The largest extent of Gleysols is in northern <a href="/facts/Russia/jfkCwyxn">Russia</a>, <a href="/facts/Siberia/oaCoPEjF">Siberia</a>, <a href="/facts/Canada/cWWFM8oc">Canada</a>, <a href="/facts/Alaska/LlDNr2uR">Alaska</a>, <a href="/facts/China/lTjIXY5p">China</a> and <a href="/facts/Bangladesh/NXk4f78Y">Bangladesh</a>. An estimated 200 million hectares of gleysols are found in the tropics, mainly in the <a href="/facts/Amazon_Basin/kVk5XeHA">Amazon</a> region, equatorial <a href="/facts/Africa/XkqQUP9s">Africa</a>, and the coastal swamps of <a href="/facts/Southeast_Asia/VafwT517">Southeast Asia</a>. </p> <p>They exhibit a greenish-blue-grey <a href="/facts/Soil_color/bjmqva6M">soil color</a> because of <a href="/facts/Anoxic_waters/vLdveWX0">anoxic</a> <a href="/facts/Wetland/9abbP7CR">wetland</a> conditions. On exposure, as the iron in the soil <a href="/facts/Oxidation/Pyd5RVcj">oxidizes</a> colors are transformed to a mottled pattern of reddish, yellow or orange patches. During <a href="/facts/Soil_formation/sJty93z9">soil formation</a> (<i>gleying</i>), the oxygen supply in the soil profile is restricted due to soil moisture at saturation. Anaerobic micro-organisms support cellular respiration by using alternatives to free oxygen as <a href="/facts/Electron_acceptors/1FQzB8pQ">electron acceptors</a> to support <a href="/facts/Cellular_respiration/kb6gpsvL">cellular respiration</a>. Where <a href="/facts/Anaerobic_organisms/bhQnlqCq">anaerobic organisms</a> <a href="/facts/Redox/Pyd5RVcj">reduce</a> <a href="/facts/Ferric_oxide/vam0XoC5">ferric oxide</a> to <a href="/facts/Ferrous_oxide/H9V7S3MG">ferrous oxide</a>, the reduced mineral compounds produce the typical gleysoil color. <a href="/facts/Green_rust/nGtySEbh">Green rust</a>, a <a href="/facts/Layered_double_hydroxide/gWBuQLJx">layered double hydroxide</a> (LDH) of Fe(II) and Fe(III) can be found as the mineral <a href="/facts/Fougerite/LRSzzcRX">fougerite</a> in gleysoils. </p><p>Gleysoils 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 <a href="/facts/Permeability_(fluid)/ja7dRwgU">permeable</a> lower <a href="/facts/Soil_horizons/GcXhdams">horizons</a>, including, for example, some sands in hollows within sand dune systems (known as slacks), and in some <a href="/facts/Alluvial/Bo78QRlp">alluvial</a> situations. </p><p>Groundwater gleysoils develop where <a href="/facts/Drainage/thEd3nfB">drainage</a> is poor because the <a href="/facts/Water_table/2j0VD0lF">water table</a> (<a href="/facts/Phreatic/gLkXmML2">phreatic</a> surface) is high, whilst surface-water gleying occurs when <a href="/facts/Precipitation_(meteorology)/uq3nGQc8">precipitation</a> input at the surface does not drain freely through the ground. A reducing environment exists in the saturated layers, which become mottled greyish-blue or greyish-brown due to its <a href="/facts/Ferrous_iron/TCxvdjfW">ferrous iron</a> and organic matter content. 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. </p><p>In the <a href="/facts/World_Reference_Base_for_Soil_Resources/dQ5xGQ69">World Reference Base for Soil Resources</a> (WRB), soils with <a href="/facts/Redox/Pyd5RVcj">redox</a> processes due to ascending <a href="/facts/Groundwater/JYM2IDS2">groundwater</a> belong to the Reference Soil Group Gleysols. Soils with redox processes due to <a href="/facts/Water_stagnation/1cbBED8V">stagnant water</a> are <a href="/facts/Stagnosol/SPbbMm52">Stagnosols</a> and <a href="/facts/Planosol/oQqJuJg9">Planosols</a>. </p>