sol-, -sol +
(Latin: base, ground, soil, bottom; the lowest part of something; sole of the foot or a shoe)
Soil orders are named by adding the suffix -sol to a root word, as shown in the table of the United States Soil Taxonomy and the soil classification system of the Food and Agriculture Organization, FAO (agency of the United Nations).
Many of the applicable soilwords which are listed and defined in this unit do not use the -sol suffix; however, they are included because they are essential parts of the major listings of the U.S. Soil Taxonomy and the Food and Agriculture Organization presentations.
The soil groups are based on extensive sets of field and laboratory observations and on extensive technical criteria.
This fertile surface horizon, known as a mollic epipedon, comes from the long-term addition of organic materials which are derived from plant roots.
Mollisols are among some of the most important and productive agricultural soils in the world and are extensively used for this purpose.
Mollisols are divided into eight suborders: Albolls, Aquolls, Rendolls, Gelolls, Cryolls, Xerolls, Ustolls, and Udolls all of which are available in this unit.
2. From the U.S. Soil Taxonomy soil-order classification system.3. Etymology: from Latin mollis, "soft".
They are perhaps the most inherently fertile of the tropical soils because of their high nutrient content and deep, permeable structures and they are utilized widely for plantation agriculture.
Nitisols technically include a significant accumulation of clay (30 percent or more by mass and extend as much as 150 cm [5 feet] below the surface) and by a blocky aggregate structure.
Iron oxides and high water content are believed to contribute significantly in creating the soil structure.
Nitisols are also strongly influenced by biological activity, resulting in a homogenization of the upper portion of the soil profile.
These soils are related to the Alfisol and Inceptisol orders of the U.S. Soil Taxonomy and related FAO soil groups originating in tropical climates and also containing layers with clay accumulations are Acrisols and Lixisols.
2. From the classification system of the Food and Agriculture Organization, FAO.3. Etymology: from Latin nitidus, "shiny".
2. A suborder of the soil order Entisol, well drained and of medium or fine texture; usually shallow to bedrock and lacking evidence of horizonation (formation of soil horizons) and occurs mostly on strong slopes.
Most nutrients in Oxisol ecosystems are contained in the vegetation and decomposing plant material which are divided into five suborders: Aquox, Torrox, Ustox, Perox, and Udox that are defined in this unit.
2. From the U.S. Soil Taxonomy soil-order classification system.3. Etymology: from French oxi, "oxide".
They are highly arable (plowable) soils and are used for growing wheat, soybeans, and pasture for cattle, as well as for wood and fuel production.
Occupying about 1.5 percent of the continental land area on earth, Phaeozems are found principally in the North American prairies, the South American pampas, and the subtropical steppes of Asia.
Phaeozems have a high content of available calcium ions bound to soil particles, resulting in a very permeable, well-aggregated structure.
These soils occur in association with Chernozems but under more humid climatic conditions (more than 550 millimeters [22 inches] of rainfall per year), which results in the absence of calcium carbonate or salt accumulation in subsurface layers.
They may exhibit a layer of clay accumulation and their surface layers are usually higher in humus than those of Chernozems.
2. From the classification system of the Food and Agriculture Organization, FAO.3. Etymology: from Greek-Russian phaios zemlja, "dusky earth".
They occur typically in wet low-lying areas which can support either grass or open forest vegetation.
They are lacking in plant nutrients; however, and their clay content leads to both seasonal waterlogging and drought stress.
Under careful management they can be cultivated for rice, wheat, or sugar beets; but, their principal use is for animal grazing.
Occupying about one percent of the total continental land area on earth, they are found primarily in Brazil, northern Argentina, South Africa, eastern Australia, and Tasmania.
The characteristic clay-rich layer of Planosols can form from a downward translocation (migration) of clay particles under the action of percolating water, from burial of a clay-rich layer by over-washed coarse material, or from seasonal destruction and translocation of clay (a process known as ferrolysis).
The clay layer may lie under an extensively leached (and hence nutrient-poor) layer.
Planosols are related to the Alfisols and Ultisols of the U.S. Soil Taxonomy while Related FAO soil groups also exhibiting clay migration are Luvisols and Albeluvisols.
2. From the classification system of the Food and Agriculture Organization, FAO.3. Etymology: from Latin planus, "flat".
They are defined by a subsurface layer containing an iron-rich mixture of clay minerals (chiefly kaolinite) and silica that hardens on exposure into ironstone concretions known as plinthite.
The impenetrability of the hardened plinthite layer, as well as the fluctuating water table which produces it, restrict the use of these soils to grazing or forestry, although the hardened plinthite has value as subgrade material for roads or even as iron ore (the iron oxide content can be as high as 80 percent by mass).
Plinthosols occupy about 0.5 percent of the total continental land area on earth, mainly in Brazil and West Africa. A related FAO soil group also originating in the tropics is Nitisol.
2. From the classification system of the Food and Agriculture Organization, FAO.3. Etymology: from Greek plinthos, "brick".
They have a characteristic subsurface layer known as the spodic horizon made up of accumulated humus and metal oxides, usually iron and aluminum.
Above the spodic horizon, there is often a bleached-out layer from which clay and iron oxides have been leached, leaving a layer of coarse-textured material containing primary minerals and little organic matter.
Podzols usually are unacceptable for cultivation because of their acidity and climatic environment.
Occupying almost four percent of the total continental land area on earth, they range from Scandinavia to Russia and Canada in the Northern Hemisphere, to The Guianas near the Equator, to Australia and Indonesia in the Southern Hemisphere.
Podzols are closely similar to the Spodosol order of the U.S. Soil Taxonomy while Albeluvisols are a related FAO soil group which also present a bleached-out layer.
2. From the classification system of the Food and Agriculture Organization, FAO.3. Etymology: from Russian pod zola, "under ash".
Regosols occur mainly in polar and desert regions, occupying about two percent of the continental land area on earth, principally in northern China, Greenland, Antarctica, north-central Africa, the Middle East, and northwest Australia.
They are usually found under their original natural vegetation or under limited dryland cropping.
Regosols often show accumulations of calcium carbonate or gypsum in hot, dry climatic zones and in very cold climatic zones they contain permafrost within two meters (about six feet) of the land surface.
Regosols are similar to the soils in the Entisol order of the U.S. Soil Taxonomy that occur in either very cold or very dry and hot climatic zones.
They differ from the FAO soil groups Andosols, Arenosols, and Vertisols in parent materials, from Gleysols which has lower water content, and from Leptosols that has greater soil profile depth.
2. From the Food and Agriculture Organization, FAO system.3. Etymology: from Greek rhegos, "blanket".
