Arkansas, Mississippi, Missouri, and Tennessee
93,600 km² (36,140 mi²)

    Land use: Most of this area is in farms. About 55 percent is cropland, 35 percent woodland, and 7 percent pasture. About 3 percent is used for miscellaneous purposes. Cropland makes up about three-fourths of the acreage in the north and less than one-fourth in the south. The proportion of forest land varies inversely with that planted to crops; the proportion of pasture is a little higher in the south. This is an important cash-crop area. Soybeans, cotton, and wheat grown by highly mechanized methods are the major crops throughout the area. Corn is an important crop in Missouri. Rice is an important crop in Arkansas, Louisiana, and Mississippi, and sugarcane is important in southern Louisiana. Controlling surface water and artificially draining the wet soils are major concerns of management.
    Elevation and topography: Elevation is at sea level in the south and increases gradually to about 200m in the north. The area consists of level to gently sloping broad flood plains and low terraces. Most of the area is flat. The only noticeable slopes are sharp terrace scarps and natural levees that rise sharply to several meters above adjacent bottom lands or stream channels. Swamps are significant in the extreme southern part in Louisiana.
    Climate: Average annual precipitation-1,150 to 1,650 mm, increasing from north to south. In most of the area maximum precipitation is in winter and early in spring, decreasing gradually to a minimum in autumn. Along the Gulf Coast, maximum precipitation is in midsummer and early in autumn. Snowfall is negligible. Average annual temperature-14 to 21°C, increasing from north to south. Average freeze-free period-200 to 340 days, increasing from north to south.
    Water: Precipitation, streamflow, and aquifers supply moderate to large quantities of potable ground water. The Mississippi River crosses the area from north to south, and many of its tributaries also cross the area. Oxbow lakes and bayous are extensive throughout. Potable ground water is not available in extreme southern Louisiana.
    Soils: The dominant soils are Aquepts, Aqualfs, Aquents, Udolls, and Udalfs. They are deep, medium textured and fine textured soils that have an udic or aquic moisture regime, a thermic temperature regime, and mostly montmorillonitic or mixed mineralogy. Fine textured Haplaquepts (Alligator, Perry, Portland, Sharkey, and Tunica series), Hapludolls (Desha, Bowdre series), and Ochraqualfs (Jackport series), and medium textured Fluvaquents (Commerce, Mhoon, and Convent series), Natraqualfs (Foley series), Ochraqualfs (Dundee, Amagon, and Hebert series), and Hapludalfs (Dubbs, Bosket, and Rilla series) occupy backswamp areas and older natural levees. Minor soils include moderately coarse textured Dystrochrepts (Beulah series) and Udifluvents (Robinsonville series), medium textured Fluvaquents (Gideon series), fine textured Hydraquents (Barbary series), and organic Medisaprists (Maurepas series). The Hydraquents and Medisaprists are in the extreme southern part in Louisiana.
    Potential natural vegetation: This area supports deciduous bottom land forest vegetation. Willow oak, water oak, Nuttall oak, swamp white oak, sweetgum, water tupelo, baldcypress, native pecans, and hickories are the principal species. Black willow, eastern cottonwood, sycamore, sugarberry, and green ash are dominant on the more recent soils. Switchgrass, eastern gamagrass, little bluestem, indiangrass, Florida paspalum, plumegrass, sedges, and rushes are the dominant understory species.

Data Source:
U. S. Department of Agriculture, Soil Conservation Service. 1981.
       Land Resource Regions and Major Land Resource Areas of the United States.
       Agriculture Handbook 296.U. S. Government Printing Office, Washington, D. C.

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