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.

Spodosols existing in cold climates.
Mollisols of cold climates.
Cryosol, Cryosols
1. Soils that are characterized by frozen soil within one meter (39 inches) of the land surface and by waterlogging during periods of thaw.

They often show disrupted soil layers, cracks, or patterned surface features; such as, frost mounds, caused by the physical actions of ice formation and melting.

Cryosols may be either mineral soils or humus-rich materials which occupy about 17.7 million square km (6.83 million square miles) in the Arctic regions and in Antarctica, Cryosols are found principally in the wilds of Alaska, Canada, China, and Russia in the Northern Hemisphere and they are associated frequently with Gleysols, Histosols, and Podzols.

2. From the classification system of the Food and Agriculture Organization, FAO.
3. Etymology: from Greek kryros, "cold".
Aridisols with a cemented subsurface horizon.
Durisol, Durisols
1. Soils that exist in semiarid environments which have a substantial layer of silica within one meter (39 inches) of the land surface.

The silica occurs either as weakly cemented nodules or as hardpan and accumulates as a result of downward translocation (migration) when solubilized during weathering of the soil.

Durisols are found in the southwestern United States, Chile, South Africa, and especially in Australia, where rainfall is low.

They usually exist in association with Arenosols, Calcisols, Cambisols, Gypsisols, or Vertisols.

Soils in the Aridisol and Vertisol orders of the U.S. Soil Taxonomy that exhibit hardened layers of silica accumulation are closely related to the Durisols.

2. From the classification system of the Food and Agriculture Organization, FAO.
3. Etymology: from Latin durum, "hard".
Entisol, Entisols
1. Soils of slight and recent development, common along rivers and flood plains.
2. Soils with little or no morphological development.
3. Soils which are very young and may be only years or decades old; however, in cold climates or other places where chemical weathering is slow, entisols may be much older.

Different subtypes are found in Labrador's glacial deposits, northern China's flood deposits, and the Kalahari's dune deposits in Africa.

Enttisols are divided into six suborders: Wassents, Aquents, Arents, Psamments, Fluvents, and Orthents; all of which are defined alphabetically in other locations of this unit.

4. From the U.S. Soil Taxonomy soil-order classification system.
5. Etymology: apparently from the ent in Latin recentem, "recent; lately done or made, new, fresh".
Ferralsol, Ferrasols
1. Red and yellow weathered soils with colors which result from an accumulation of metal oxides, particularly iron and aluminum (from which the name of the soil group is derived).

They are formed on geologically old parent materials in humid tropical climates, with rainforest vegetation growing in the natural state.

Because of the residual metal oxides and the leaching of mineral nutrients, they have low fertility and require additions of lime and fertilizer if they are to be used for agriculture.

Tree crops; such as, oil palm, rubber, or coffee are suitable; but pastures are often their main agricultural use after the original forest is cleared.

Occupying just below six percent of the continental land surface on earth, Ferralsols are found mainly in Brazil, the Congo River basin, Guinea, and Madagascar.

Ferralsols are technically defined by a fine-textured subsurface layer of low silt-to-clay ratio, high contents of kaolinitic clay and iron and aluminum oxides, and low amounts of available calcium or magnesium ions.

Ferralsols are related to the Oxisol order of the U.S. Soil Taxonomy. Related FAO soil groups originating in tropical climates and composed of weathered soils with high iron or aluminum content are Plinthosols and Alisols.

2. From the classification system of the Food and Agriculture Organization, FAO.
3. Etymology: from Latin ferrum alumen, "iron-aluminum".
Histosols that are primarily made up of only slightly decomposed organic materials, often called peat.
Alluvial Entisols commonly found on floodplains.
Fluvisol, Fluvisols
1. Typically found on level topography that is flooded periodically by surface waters or rising groundwater, as in river floodplains and deltas and in coastal lowlands.

Fluvisols are cultivated for dryland crops or rice and are used for grazing during the dry seasons.

Fluvisols are technically defined by a weak or nonexistent surface horizon (uppermost layer) and by parent material derived from river, lake, or marine sediments which have been deposited at regular intervals or in the recent past.

These soils exhibit a stratified profile which reflects their depositional history or an irregular layering of humus (nonliving, finely divided organic matter in soil, derived from microbial decomposition of plant and animal substances) and mineral sediments in which the content of organic carbon decreases with depth and wide variations in texture and mineral composition are observed.

Fluvisols are related to the Inceptisol and Entisol orders of the U.S. Soil Taxonomy, wherever the latter occur on floodplains and deltas.

Fluvisols are sometimes found in conjunction with Gleysols, a related FAO soil group formed under the influence of water.

2. From the classification system of the Food and Agriculture Organization, FAO.
3. Etymology: from Latin fluvius, "river".
Histosols that are not saturated with water for long periods during the year.
Andisols of very cold climates.
Inceptisols of very cold climates.
Gelisol, Gelisols
1. Soils of very cold climates that contain permafrost within two meters of the surface.

Gelisols soils are geographically limited to high-latitude polar regions and localized areas at high mountain elevations.

Because of the extreme environment in which they are found, Gelisols support the lowest population percentage of any of the soil orders.

Gelisols are divided into three suborders: Histels, Turbels, and Orthels all of which are defined in other parts of this unit.

2. From the U.S. Soil Taxonomy soil-order classification system.
3. Etymology: from Greek gelid, "very cold".
Spodosols of very cold climates.

Much of the information presented in this unit was compiled from the following sources:

Encyclopædia Britannica Online; "U.S. Soil Taxonomy"; December 19, 2010.

Soil and Land Resources Division, by Dr. Paul McDaniel;
University of Idaho, Moscow, Idaho; College of Agricultural and Life Sciences;

The National Geographic Desk Reference; A Stonesong Press Book;
National Geographic Society; Washington, D.C.; 1999; pages 224-227.