sol-, -sol +

Mollisols of very cold climates.

1. Formed under waterlogged conditions and produced by rising groundwater.

In the tropics and subtropics Gleysols are cultivated for rice or, after drainage, for field crops and trees.

They are found in the polar regions (Alaska and Arctic Asia; about half of all Gleysols) are frozen at shallow depth and are used only by wildlife.

These soils occupy about 5.7 percent of the continental land area on earth, including the Mississippi valley, north-central Argentina, central Africa, the Yangtze River valley, and Bangladesh.

Gleysols are technically characterized by both chemical and visual evidence of iron reduction.

Subsequent downward translocation (migration) of the reduced iron in the soil profile is associated with gray or blue colors in subsurface horizons (layers).

Wherever oxidation of translocated iron has occurred (in fissures and cracks that may dry out), red, yellow, or brown mottles may be seen.

Gleysols are related to the Entisol and Inceptisol orders of the U.S. Soil Taxonomy, wherever the latter occur under waterlogged conditions sufficient to produce visual evidence of iron reduction.

In warm climatic zones these soils occur in association with the FAO soil groups Fluvisol and Cambisol.

2. From the classification system of the Food and Agriculture Organization, FAO.
3. Etymology: from Russian gley, "mucky soil mass".

Aridisols with accumulations of gypsum.

1. Soils that are characterized by a subsurface layer of gypsum (a hydrated calcium sulfate) accumulated by the precipitation of calcium and sulfate from downward percolating waters in the soil profile.

With intensive management, irrigated crops can be grown on these soils.

Occupying about 0.7 percent of the continental land area on earth, Gypsisols occur in the very arid (dry) areas of the world (North Africa, the Middle East), sometimes in association with Calcisols, as in Australia and the United States.

In order to qualify as a Gypsisol, a soil may also have layers of accumulated clay or of calcium carbonate, but not of soluble salts, and it may not show waterlogging or swelling-clay effects.

Little soil horizon (layer) differentiation is present except for the gypsic layer (which may be hardened and compact), with gypsum crystallites forming pebbles, stones, or rosettes (the so-called desert rose, in which gypsum crystals cluster together as do the petals of a rose).

2. From the classification system of the Food and Agriculture Organization, FAO.
3. Etymology: from Latin gypsum, "calcium sulfate".

Histosols which are mainly made up of moderately decomposed organic materials.

Gelisols which have large quantities of organic matter.

1. Soils which are composed primarily of organic materials.

Most Histosols are formed in settings; such as, wetlands where restricted drainage diminishes the decomposition of plant and animal remains, allowing these organic materials to accumulate over time.

Histosols are often referred to as peats and mucks which are mined for fuel and horticultural products.

Histosols are divided into five suborders: Folists, Wassists, Fibrists, Saprists, and Hemists all of which are defined in other word entries of this unit.

2. From the U.S. Soil Taxonomy soil-order classification system.
3. Etymology: from Greek histos, "tissue".

Well-drained Spodosols that contain relatively large quantities of organic matter.

Well-drained Ultisols which have high organic matter content.

1. A form of soil in which adequate water is available to start the development of horizons (soil layers with different physical, chemical, and biologic characteristics), but the soils have not reached an equilibrium with their environments; in other words, soils with weakly developed subsurface horizons.

Inceptisols are found on steeper slopes; such as, those in the Appalachians, where mass wasting is common and cold temperatures freeze soil water, thus slowing pedogenic processes (origin, formation, and development of soil) , and on floodplains with frequent deposits of sediments.

Inceptisols are divided into seven suborders: Aquepts, Anthrepts, Gelepts, Cryepts, Ustepts, Xerepts, and Udepts and are defined individually in this unit.

2. From the U.S. Soil Taxonomy soil-order classification system.
3. Etymology: from Latin inceptum, "beginning".

1. The inner sole of a shoe or boot.
2. A thin removable liner placed inside a shoe to make it warmer or more comfortable or to prevent the buildup of odor.
3. Etymology: "bottom of the foot" c.1325, from Old French sole, from Latin solea, "sandal, bottom of a shoe"; from solum, "bottom, ground, soil".

1. Humus-rich soils which were originally covered with early-maturing native grassland vegetation, that produces a characteristic brown surface layer.

They are found in relatively dry climatic zones (200–400 millimeters [8–16 inches] of rainfall per year), usually bordering arid regions; such as, southern and central Asia, northern Argentina, the western United States, and Mexico.

Kastanozems are principally used for irrigated agriculture and grazing and have relatively high levels of available calcium ions bound to soil particles.

These and other nutrient ions move downward with percolating water to form layers of accumulated calcium carbonate or gypsum.

Kastanozems are related to the soils in the Mollisol order of the U.S. Soil Taxonomy which form in semiarid regions under relatively scarce grasses and shrubs.

Related FAO soil groups originating in a steppe environment are Chernozems and Phaeozems.

2. From the classification system of the Food and Agriculture Organization, FAO.
3. Etymology: from Latin-Russian castanea zemlja, "chestnut earth".

1. Soils with a very shallow profile depth (indicating little influence of soil-forming processes), and they often contain large amounts of gravel.

They typically remain under natural vegetation, being especially susceptible to erosion, desiccation, or waterlogging, depending on climate and topography.

Leptosols are approximately equally distributed among high mountain areas, deserts, and boreal or polar regions, where soil formation is limited by severe climatic conditions.

They are the most extensive soil group worldwide, occupying about thirteen percent of the total continental land area on earth, principally in South America, Canada, the Sahara, the Middle East, central China, Europe, and Asia.

Because of continual wind or water erosion or shallow depth to hard bedrock, Leptosols show little or none of the horizonation, or layering, characteristic of other soils.

Leptosols are related to the soils in the Entisol order of the U.S. Soil Taxonomy which are found in high mountains, deserts, or boreal, and polar regions of the world.

Regosols are a related FAO soil group originating from erosion processes.

2. From the classification system of the Food and Agriculture Organization, FAO.
3. Etymology: from Greek leptos, "thin".

1. Soils that develop on old landscapes in a tropical climate with a usual dry season.

Their age and mineralogy have led to low levels of plant nutrients and a high erodibility, making agriculture possible only with frequent fertilizer applications, minimum tillage, and careful erosion control.

Perennial crops are more suitable for these soils than root or tuber crops and they occupy just under 3.5 percent of the continental land area on earth, primarily in east-central Brazil, India, and West Africa.

Lixisols are defined by the presence of a subsurface layer of accumulated kaolinitic clays, where at least half of the readily displaceable ions are calcium, magnesium, sodium, or potassium; but they are also identified by the absence of an extensively leached layer below the surface horizon (uppermost layer).

They are related to the Oxisol order of the U.S. Soil Taxonomy and the related FAO soil groups originating in tropical climates and also containing layers with clay accumulations are Acrisols and Nitisols.

2. From the classification system of the Food and Agriculture Organization, FAO.
3. Etymology: from Latin lixivia, "washing".

1. The mixed mineralogy, high nutrient content, and good drainage of these soils make them suitable for a wide range of agriculture, from grains to orchards to vineyards.

Luvisols form on flat or gently sloping landscapes under climatic regimes that range from cool temperate to warm Mediterranean.

Occupying just over five percent of the total continental land area on earth, they are found typically in west-central Russia, the United States, central Europe, the Mediterranean basin, and southern Australia.

Luvisols are technically characterized by a surface accumulation of humus overlying an extensively leached layer that is nearly empty of clay and iron-bearing minerals.

Below the latter lies a layer of mixed clay accumulation that has high levels of available nutrient ions comprising calcium, magnesium, sodium, or potassium.

Luvisols are often associated with Cambisols and Albeluvisols are a related FAO soil group also exhibiting clay migration.

2. From the classification system of the Food and Agriculture Organization, FAO.
3. Etymology: from Latin luere, "to wash".