How2Day: Types of Soil in the United States

One soil type that contains clay and iron. Arid soil image by Igor Baryshev from Fotolia.com
Soil is classified into different orders just like plants are classified into different types. Twelve different soil orders exist, and within these orders are different suborders. Soils are composed of different percentages of clay, sand and loam. Each type has different moisture, mineral and organic content. The environment where the soil is found plays heavily into the soil composition.

Gelisol is found at high latitude areas. It is typically found at high elevations where permafrost is found within two meters of the surface. Gelisol soil contains high levels of carbon but little life due to the extreme low temperatures. In the United States, 8.7 percent of the soil is Gelisol. Orthels, Turbels and Histels are the three suborders found within this soil order.

Histosols are organic soils that contain high amounts of organic material. This soil is typically found in wetlands where decomposition can accumulate. Approximately 1.6 percent of the soil in the United States is Histosol. Common names for this soil order are mucks and peats. The five suborders within this soil type are Hemists, Saprists, Fibrists, Wassists and Folists. Fuel and horticulture products are found in Histosol soils.

Spodosols are acidic soils that contain iron and aluminum. This soil looks reddish brown due to the higher levels of metal. Spodosol soils are found in moist, cool climates where coniferous forests are found. In the United States, Spodosols make up 3.5 percent of soil. The five different soil suborders in this soil type are Orthods, Humods, Cryods, Gelods and Aquods.

Andisol soils are made of volcanic ash and other volcanic material. Ferrihydrite, Imogolite, Allophane and glass are found at high levels in Andisol. Because of these chemicals in the soil, Andisol is able to hold large amounts of water and can fix phosphorus. Only 1.7 percent of the land in the United States contains Andisols, making it the least extensive of the soil types. The eight soil suborders within the Andisol order are Udands, Ustands, Vitrands, Xerands, Torands, Cryands, Gelands and Aquands.

Oxisols are only found in Hawaii. These are found at intertropical areas and are rich in aluminum oxide and iron oxide. Because of the oxides, there are very low levels of nutrients in the soil. Most of the soil nutrient comes from plant material and other vegetation. The five suborders to this soil order are Udox, Perox, Ustox, Torrox and Aquox. Only 0.2 percent of the land in the United States is Oxisol.

Vertisols contain high levels of clay that will swell and shrink depending on the moisture content. When the weather is dry the soil shrinks and cracks form. About two percent of the land in the United States is Vertisol. Most of this 2 percent is found in the state of Texas. The six suborders within Vertisol are Uderts, Ustertes, Torrets, Xererts, Cryerts and Aquerts.

Aridisols contain calcium carbonate and tend to be very dry. Calcium carbonate, gypsum and soluble salts will leach from the soil when moisture is present. Ardisols make up 8.3 percent of the land in the United States. This type of soil is typically used for wildlife, range and conservation areas. Farming is not done on this soil unless irrigation is available. The seven suborders within Aridisols are Cambids, Calcids, Argids, Gypsids, Dunds, Salids and Cryids.

Ultisols are found in the forest and are acidic soils. These are found in tropical climates where it is humid. The color of the soil is normally red due to high levels of iron. Over 9.2 percent of the land in the United States is composed of Ultisols. The low levels of magnesium, calcium and potassium in the soil do not support agricultural growth but they do favor tree and forest growth. The five suborders within this soil order are Xerults, Ustults, Udults, Humults and Aquults.

Mollisols support grasslands. They tend to be dark and thick. These soils are found in the prairie region of the United States in the middle latitudes. This is the most extensive soil in the United States, comprising 21.5 percent of the land. The eight suborders within the Mollisol order include Udolls, Ustolls, Xerolls, Cryolls, Gelolls, Rendolls, Aquolls and Albolls.

Alfisol soils have high fertility rates and are formed underneath forests. These are found in sub-humid and humid regions. Alfisol soils make up 13.9 percent of the land in the United States. These soils are used extensively in silviculture and agriculture. The five suborders within this soil type are Xeralfs, Ustalfs, Udalfs, Cryalfs and Aqualfs.

Inceptisols occur in many different ecological systems. A lot of mountains, watershed and forestry land is comprised of Inceptisols. In the United States, Inceptisols make up 9.7 percent of the land. The seven different types of Inceptisol soils include Udepts, Xerepts, Ustepts, Cryepts, Gelepts, Anthrepts and Aquepts.

Many different types of soils exist within the Entisol soil order. Entisol soils are those that do not easily fit into the other 11 soil orders. These soils are typically found by shore deposits, large river valleys and rocky settings. Entisols comprise 12.3 percent of the land in the United States. The six suborders within this soil order are Orthents, Fluvents, Psammants, Arents, Aquents and Wassents.

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