Stagnosol
Encyclopedia
A stagnosol in the FAO
World Reference Base for Soil Resources
is a soil
with strong mottling of the soil profile due to redox processes
caused by stagnating surfacewater
. Stagnosols are periodically wet and mottled
in the topsoil and subsoil, with or without concretion
s and/or bleaching. The topsoil can also be completely bleached (albic horizon
). A common name in many national classification systems for most Stagnosols is pseudogley. In the USDA soil taxonomy
, many of them belong to the Aqualfs, Aquults, Aquents, Aquepts and Aquolls.
They are developed in a wide variety of unconsolidated materials like glacial till, and loam
y aeolian, alluvial and colluvial
deposits
and physically weathered
siltstone. Stagnosols occur on flat to gently sloping land in cool temperate to subtropical
regions with humid
to perhumid climate conditions.
The agricultural
suitability of Stagnosols is limited because of their oxygen
deficiency resulting from stagnating water above a dense subsoil. Therefore, they have to be drained. However, in contrast to Gleysols
, drainage with channels or pipes is in many cases insufficient. It is necessary to have a higher porosity
in the subsoil in order to improve the hydraulic conductivity
. This may be achieved by deep loosening or deep ploughing. Drained Stagnosols can be fertile
soils owing to their moderate degree of leaching.
Stagnosols cover 150–200 million ha worldwide. For the greater part in humid to perhumid temperate regions of West
and Central Europe
, North America
, southeast Australia
and Argentina
. Here Stagnosols are associated with Luvisols as well as silt
y to clay
ey Cambisols
and Umbrisols. They also occur in humid to perhumid subtropical regions, where thet are associated with Acrisols and Planosols.
with a light-coloured, coarse-textured
, surface horizon
that shows signs of periodic water
stagnation and abruptly overlies a dense, slowly permeable subsoil with significantly more clay than the surface horizon. In the US Soil Classification of 1938 used the name Planosols, whereas its successor, the USDA soil taxonomy
, includes most Planosols in the Great Groups Albaqualfs, Albaquults and Argialbolls.
Fão
Fão is a town in Esposende Municipality in Portugal....
World Reference Base for Soil Resources
World Reference Base for Soil Resources
The World Reference Base for Soil Resources is the international standard taxonomic soil classification system endorsed by the International Union of Soil Sciences . It was developed by an international collaboration coordinated by the International Soil Reference and Information Centre and...
is a soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
with strong mottling of the soil profile due to redox processes
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
caused by stagnating surfacewater
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
. Stagnosols are periodically wet and mottled
Gley soil
Gley soil in soil science is a type of hydric soil which exhibits a greenish-blue-grey soil color due to wetland conditions. On exposure to the air, gley colors are transformed to a mottled pattern of reddish, yellow or orange patches. During gley soil formation , the oxygen supply in the soil...
in the topsoil and subsoil, with or without concretion
Concretion
A concretion is a volume of sedimentary rock in which a mineral cement fills the porosity . Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin con meaning 'together' and crescere meaning 'to grow'...
s and/or bleaching. The topsoil can also be completely bleached (albic horizon
Soil horizon
A soil horizon is a specific layer in the land area that is parallel to the soil surface and possesses physical characteristics which differ from the layers above and beneath. Horizon formation is a function of a range of geological, chemical, and biological processes and occurs over long time...
). A common name in many national classification systems for most Stagnosols is pseudogley. In the USDA soil taxonomy
USDA soil taxonomy
USDA Soil Taxonomy developed by United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate classification of soil types according to several parameters and in several levels: Order, Suborder, Great Group, Subgroup, Family, and Series.- Example of...
, many of them belong to the Aqualfs, Aquults, Aquents, Aquepts and Aquolls.
They are developed in a wide variety of unconsolidated materials like glacial till, and loam
Loam
Loam is soil composed of sand, silt, and clay in relatively even concentration . Loam soils generally contain more nutrients and humus than sandy soils, have better infiltration and drainage than silty soils, and are easier to till than clay soils...
y aeolian, alluvial and colluvial
Colluvium
Colluvium is the name for loose bodies of sediment that have been deposited or built up at the bottom of a low-grade slope or against a barrier on that slope, transported by gravity. The deposits that collect at the foot of a steep slope or cliff are also known by the same name. Colluvium often...
deposits
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
and physically weathered
Weathering
Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...
siltstone. Stagnosols occur on flat to gently sloping land in cool temperate to subtropical
Subtropics
The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...
regions with humid
Humid subtropical climate
A humid subtropical climate is a climate zone characterized by hot, humid summers and mild to cool winters...
to perhumid climate conditions.
The agricultural
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
suitability of Stagnosols is limited because of their oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
deficiency resulting from stagnating water above a dense subsoil. Therefore, they have to be drained. However, in contrast to Gleysols
Gleysols
A Gleysol in the FAO World Reference Base for Soil Resources is a wetland soil that, unless drained, is saturated with groundwater for long enough periods to develop a characteristic gleyic colour pattern...
, drainage with channels or pipes is in many cases insufficient. It is necessary to have a higher porosity
Porosity
Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0–1, or as a percentage between 0–100%...
in the subsoil in order to improve the hydraulic conductivity
Hydraulic conductivity
Hydraulic conductivity, symbolically represented as K, is a property of vascular plants, soil or rock, that describes the ease with which water can move through pore spaces or fractures. It depends on the intrinsic permeability of the material and on the degree of saturation...
. This may be achieved by deep loosening or deep ploughing. Drained Stagnosols can be fertile
Fertile
The term fertile describes a condition whereby organisms are able to produce physically healthy offspring.Fertile may also refer to:...
soils owing to their moderate degree of leaching.
Stagnosols cover 150–200 million ha worldwide. For the greater part in humid to perhumid temperate regions of West
Western Europe
Western Europe is a loose term for the collection of countries in the western most region of the European continents, though this definition is context-dependent and carries cultural and political connotations. One definition describes Western Europe as a geographic entity—the region lying in the...
and Central Europe
Central Europe
Central Europe or alternatively Middle Europe is a region of the European continent lying between the variously defined areas of Eastern and Western Europe...
, North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, southeast Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. Here Stagnosols are associated with Luvisols as well as silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
y to clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
ey Cambisols
Cambisols
A Cambisol in the FAO World Reference Base for Soil Resources is a soil with a beginning of soil formation. The horizon differentiation is weak...
and Umbrisols. They also occur in humid to perhumid subtropical regions, where thet are associated with Acrisols and Planosols.
with a light-coloured, coarse-textured
Soil texture
Soil texture is a qualitative classification tool used in both the field and laboratory to determine classes for agricultural soils based on their physical texture. The classes are distinguished in the field by the 'textural feel' which can be further clarified by separating the relative...
, surface horizon
Soil horizon
A soil horizon is a specific layer in the land area that is parallel to the soil surface and possesses physical characteristics which differ from the layers above and beneath. Horizon formation is a function of a range of geological, chemical, and biological processes and occurs over long time...
that shows signs of periodic water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
stagnation and abruptly overlies a dense, slowly permeable subsoil with significantly more clay than the surface horizon. In the US Soil Classification of 1938 used the name Planosols, whereas its successor, the USDA soil taxonomy
USDA soil taxonomy
USDA Soil Taxonomy developed by United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate classification of soil types according to several parameters and in several levels: Order, Suborder, Great Group, Subgroup, Family, and Series.- Example of...
, includes most Planosols in the Great Groups Albaqualfs, Albaquults and Argialbolls.