Introduction The USDA soil taxonomic developed by United States Department of Agriculture and the National Cooperative Soil Survey provides hierarchy includes orders, suborders, great groups, subgroups, families and series, with each series representing a unique kind of soil. In the United States, over 19,000 soil series have been identified. The percentages of land area (in the US and associated territories, etc.) occupied by soils of the twelve orders have been estimated. Each state and territory in the United States has a representative soil
Types of soils 1 Alfisols Soil 6 Inceptisol 2 Andisol Soil 7 Mollisol Soil 3 Aridisol Soil 8 Oxisol Soil 4 Entisol Soil 9 Spodosol Soil 5 Gelisol Soil 10 Ultisol Soil 11 Vertisol Soil
1. ALFISOLS Form in semiarid to humid areas, typically under a hardwood forest cover. They have a clay-enriched subsoil and relatively high native fertility. Refers to aluminum (Al) and iron (Fe). Because of their productivity and abundance, the Alfisols represent one of the more important soil orders for food and fiber production. They are widely used both in agriculture and forestry, and are generally easier to keep fertile than other humid-climate soils. DISTRIBUTION Alfisols occupy around one-tenth of the Earth's ice-free land surface. They are dominant in many areas, such as the Ohio River basin in the United States
2. ANDISOLS Soils formed in volcanic ash. soils containing high proportions of glass and amorphous colloidal materials, Because they are generally quite young, andisol typically are very fertile except in cases where phosphorus is easily fixed (this sometimes occurs in the tropics). They can usually support intensive cropping, with areas used for wet rice. Other andisol areas support crops of fruit, maize, tea, coffee or tobacco. In the Pacific Northwest USA, andisol support very productive forests. Andisols occupy about 1% of the global ice-free land area. Most occur around the Pacific Ring of Fire, with the largest areas found in central Chile, Ecuador, Colombia, Mexico, the Pacific Northwest USA.
3. ARIDISOLS (Desert Soils) Aridisols dominate the deserts and xeric shrubland, which occupy about one third of the Earth's land surface. Aridisols have a very low concentration of organic matter, reflecting the paucity of vegetative production on these dry soils. Water deficiency is the major defining characteristic of aridisol. Also required is sufficient age to exhibit sub-soil weathering and development. Limited leaching in aridisol often results in one or more subsurface soil horizons in which suspended or dissolved minerals have been deposited: silicate clays, sodium, calcium carbonate, gypsum or soluble salts. These subsoil horizons can also be cemented by carbonates, gypsum or silica. Accumulation of salts on the surface can result in salinization. This soil found in western part of USA.
4) ENTISOLS Are defined as soils that do not show any profile development other than an A horizon. Entisols are the second most abundant soil order (after inceptisols), occupying about 16% of the global ice-free land area. Flooding or saturation areas In Mississippi, Great lake area.
5.Gelisols They are soils of very cold climates. That occurs from the alternating thawing and freezing characteristic of gelisols. in the upper layer, most gelisols are black or dark brown in soil color, followed by a shallow mineral layer. Despite the influence of glaciations in most areas where gelisols occur, chemically they are not highly fertile because nutrients, especially calcium and potassium, are very easily leached above the permafrost. The permafrost greatly restricts the engineering use of gelisols, as large structures (e.g. buildings) subside as the frozen earth thaws when they are put in place. It is found in the Canadian Shield area of USA.
6. Inceptisols They form quickly through alteration of parent material. They are more developed than entisols. They have no accumulation of clays, iron oxide, aluminum oxide or organic matter. It is a widely spared in Appalachian mountain region
7. Mollisoil Mollisols have deep, high organic matter, nutrient-enriched surface soil (A horizon), typically between 60 80 cm in depth. This fertile surface horizon, known as a mollic epipedon, is the defining diagnostic feature of Mollisols. Distrubution Mollisols form in semi-arid to semi-humid areas, typically under a grassland cover. They are most commonly found in the mid-latitudes, namely in North America, mostly east of the Rocky Mountains
8. OXISOLS The word "oxisol" comes from "oxide" in reference to the dominance of oxide minerals such as bauxite. occurrence in tropical rain forest 1525 degrees north and south of the Equator. The main processes of soil formation of oxisols are weathering, humification and pedoturbation due to animals. Oxisols are often used for tropical crops such as cocoa, rubber in case rice.
9. SPODOSOLS It is known as spodosol in China and the United States of America and podosols in Australia. These soils form in sandy materials, under climates where large amounts of water infiltrate into the soil at one or more times of the year. In Michigan, that "time of year" is during the snowmelt period, in spring. The soils form under forest, usually mixed forest types (maple, pine, hemlock, birch). They are useful for forestry and recreation. Most podzol are poor soils for agriculture due to the sandy portion, resulting in a low level of moisture and nutrients. Geographic distribution Spodosols are prevalent in the northern parts of the Great Lakes region extent podzol are most common in temperate and boreal zones of the northern hemisphere but they can also be found in other settings including both temperate rainforests and tropical areas.
10. ULTISOLS commonly known as red clay soils. They are defined as mineral soils which contain no calcareous material anywhere within the soil. Ultisols occur in humid temperate or tropical regions. The red and yellow colors result from the accumulation of iron oxide (rust), which is highly insoluble in water. Ultisols are the dominant soils in the Southern United States. Red clay soil is common throughout the Southern United States, especially around the Piedmont.
11. VERTISOLS SOIL a soil in which there is a high content of expansive clay known as montmorillonite that forms deep cracks in drier seasons or years. Vertisol typically form from highly basic rocks, such as basalt, in climates that are seasonally humid or subject to erratic droughts and floods, or that impeded drainage. Vertisols are found between 50 N and 45 S of the equator. vertisols are dominant include southern Texas and adjacent Mexico. The natural vegetation of vertisols is grassland, savanna, or grassy woodland. When irrigation is available, crops such as cotton, wheat, sorghum and rice can be grown. Vertisols are especially suitable for rice because they are almost impermeable when saturated. Rain fed farming is very difficult because vertisols can be worked only under a very narrow range of moisture conditions: they are very hard when dry and very sticky when wet.