Soils are formed from rock and sediment over long periods of time. The texture of soils is determined by the amount of weathering caused by temperature changes, moisture content and other factors. In the United States, soils are classified into 12 categories, called orders, based on the development, fertility, and organic and mineral content. Louisiana is part of 11 Major Land Resource Areas (MLRA), according to the U.S. Department of Agriculture. Most of the soils in the state are formed from alluvial sediments deposited by the Mississippi, Ouachita and Red Rivers.
Arkansas River Alluvium
The clay and loam soils of the Arkansas River Alluvium MLRA are found on the alluvial plains along the Ouachita River. The soil varies from poorly to well drained, and consists of forested wetlands and croplands. This MLRA includes the soil orders alfisols, entisols, inceptisols and vertisols.
Eastern Gulf Coast Flatlands
The Eastern Gulf Coast Flatlands MLRA is a region of low coastal plains with many large streams. The soil is poorly to very poorly drained, and it consists of sand, loam and muck. Most of this MLRA is forested with small areas of crop and pasture land. The soil orders include alfisols, entisols, histosols, spodosols and ultisols.
Gulf Coast Marsh
Although the fresh and saltwater marshes in the Gulf Coast Marsh MLRA are almost treeless, the area supports a large amount of wildlife. This MLRA is located on low narrow ridges of sand with many rivers, lakes, bayous, and tidal and manmade channels. The clay soil is poorly drained and includes entisols and histosols.
Gulf Coast Prairies
The Gulf Coast Prairies MLRA contains plains of clay and loam along the Gulf Coast. The sloped areas are well drained, while the depressions are poorly drained. This MLRA consists of crop, pasture and range lands, as well as forested areas along the rivers and stream. The soils include alfisols, mollisols and vertisols.
Red River Alluvium
The loam and clay soils of the Red River Alluvium MLRA are located on the alluvial plain along the lower Red River. The soil is poorly to moderately well drained, and includes alfisols, entisols, inceptisols and vertisols. This MLRA is mostly farmland with scattered forested wetlands.
Southern Coastal Plain
The Southern Coastal Plain MLRA is located in the extreme eastern part of the state. It consists of poorly to excessively drained loam, and it includes entisols, inceptisols and ultisols. The land is used for timber production, and as forage and crop land.
Southern Mississippi River Alluvium
The rolling alluvial plains of the Southern Mississippi River Alluvium MLRA are poorly drained loam or clay. The soils include alfisols, entisols, inceptisols and vertisols. This MLRA consists mostly of farms.
Southern Mississippi River Terraces
The land in the Southern Mississippi River Terraces MLRA is level to gently sloping. The soil consists of moderately to poorly drained silty alluvium. This MLRA is mostly alfisols and is used for timber production.
Southern Mississippi Valley Loess
Hills and steep valleys form the Southern Mississippi Valley Loess MLRA. The soil is well to poorly drained, and includes alfisols, entisols, inceptisols and ultisols. This MLRA is used for farm and pasture lands, and it includes some forests.
Western Coastal Plain
The Western Coastal Plain MLRA consists of level to steep uplands with streams, broad floodplains and terraces. The clay or loam soil is well to poorly drained, and it includes alfisols and ultisols. This MLRA consists of forested areas, farms and pastureland.
Western Gulf Coast Flatlands
The level to gently sloping Western Gulf Coast Flatlands MLRA is well to poorly drained. The soil contains silt, sand and gravel, and includes alfisols and ultisols. Most of this MLRA consists of forests and timberland, in addition to some farm and pasture lands.