135A—Alabama and Mississippi Blackland Prairie

This MLRA (shown in orange in the figure above) is in Alabama (53 percent) and Mississippi (47 percent). It makes up about 6,370 square miles (16,510 square kilometers). Tupelo, Mississippi, is the only major town in this MLRA. The small towns of Demopolis and Uniontown are in west Alabama. The cities of Montgomery and Selma are just outside this area, on terraces along the Alabama River, which bisects the MLRA. Interstates 20 and 20/59 cross parts of this area, and U.S. Highway 80 runs through the center of the part of the MLRA in Alabama. The Bienville National Forest is in the part in Mississippi.

Physiography

This area is in the East Gulf Coastal Plain Section of the Coastal Plain Province of the Atlantic Plain. The northern part of the area is a slightly elevated plain that is hilly, and the separate southwestern part is locally known as the Jackson Prairie portion of the East Gulf Coastal Plain Section in Mississippi. Elevation ranges from 100 to 590 feet (30 to 180 meters). Local relief is mainly 50 to 100 feet (15 to 30 meters).

The extent of the major Hydrologic Unit Areas (identified by four-digit numbers) that make up this MLRA is as follows: Mobile-Tombigbee (0316), 55 percent; Alabama (0315), 28 percent; Pascagoula (0317), 10 percent; and Pearl (0318), 7 percent. Tributaries of the Tombigbee, Pearl, and Pascagoula Rivers cross the part of this area in Mississippi. The valleys along the Tombigbee and Alabama Rivers separate the three parts of this area in Alabama.

Geology

Most of this area is underlain by Cretaceous-age clay, marl, soft limestone, or chalk of the Selma Group. The Jackson Prairie part, in southern Mississippi, and parts of the area in southwest Alabama are underlain by Tertiary-age clay, marl, soft limestone, or chalk of the Vicksburg and Jackson Groups.

Climate

The average annual precipitation in this area is 53 to 61 inches (1,345 to 1,550 millimeters). The maximum precipitation occurs early in winter, in spring, and in midsummer. The lowest rainfall occurs in autumn. The rainfall typically occurs during high-intensity, convective thunderstorms in summer, but some heavy rains occur during tropical storms in winter. The average annual temperature is 60 to 65 degrees F (16 to 18 degrees C), decreasing from south to north. The freeze-free period averages 250 days and ranges from 230 to 275 days, increasing in length to the south.

Water

Following are the estimated withdrawals of freshwater by use in this MLRA:

Public supply—surface water, 7.3%; ground water, 9.3%
Livestock—surface water, 2.2%; ground water, 9.3%
Irrigation—surface water, 1.8%; ground water, 7.3%
Other—surface water, 61.9%; ground water, 0.9%

The total withdrawals average 55 million gallons per day (208 million liters per day). About 27 percent is from ground water sources, and 73 percent is from surface water sources. Precipitation and perennial streams are important sources of water. Ponds provide water for livestock and are used locally for recreation. A few large reservoirs are available for recreation and other uses. The surface water in the area is suitable for all uses. Most of it is used for cooling thermoelectric power plants.

Moderately deep and deep wells are the principal sources of ground water for both domestic and municipal uses in this area. In Alabama, good-quality ground water is obtained primarily from Tertiary and Cretaceous sand aquifers. The southern part of the area in Alabama also has access to the Floridan and Citronelle aquifers. The ground water in Alabama generally is hard but is low in total dissolved solids. Most of the part of this area in Mississippi has no significant aquifers. The Cockfield silty clay and sand aquifer underlies parts of the isolated portion of this area in southern Mississippi. The water from this aquifer is soft and generally has less than 400 parts per million (milligrams per liter) total dissolved solids. It generally exceeds the color standard for drinking water, which is 15 units. The color has no known effects on health.

Soils

The dominant soil orders in this MLRA are Inceptisols and Vertisols. The soils in the area dominantly have a thermic soil temperature regime, a udic or aquic soil moisture regime, and smectitic or carbonatic mineralogy. They are shallow to very deep, generally well drained to somewhat poorly drained, and loamy or clayey. Epiaquepts (Leeper and Urbo series), Epiaquerts (Sucarnoochee and Houlka series), and Hapludolls (Catalpa series) formed in clayey alluvium on flood plains. Eutrudepts formed in loamy alluvium on flood plains (Marietta series) and in clayey sediments and residuum on uplands (Sumter series). Dystruderts (Oktibbeha, Hannon, Watsonia, and Vaiden series), Hapluderts (Brooksville, Okolona, and Houston series), and Paleudalfs (Kipling and Searcy series) formed in clayey sediments on uplands. Udorthents (Demopolis series) formed in residuum on ridges and hills.

Biological Resources

This area supports both deciduous hardwoods and conifers. Red oak, white oak, sweetgum, blackgum, loblolly pine, and shortleaf pine are the dominant overstory species. Forests of mixed oaks and loblolly pine are dominant on acid soils. Mixed hardwood forests dominate flood plains, and forests of eastern redcedar and sugarberry dominate alkaline hills and side slopes. Eastern redcedar, dogwood, and osage orange are the major midstory species. Japanese honeysuckle, greenbrier, little bluestem, native lespedezas, plumegrass, low panicums, sedges, and rushes are the dominant understory species.

Some of the major wildlife species in this area are white-tailed deer, cottontail, squirrel, turkey, bobwhite quail, and mourning dove.

Land Use

Following are the various kinds of land use in this MLRA:

Cropland—private, 16%
Grassland—private, 29%
Forest—private, 45%; Federal, 3%
Urban development—private, 4%
Water—private, 2%
Other—private, 1%

Most areas have been disturbed, and only small remnants of the former prairie vegetation remain. The major crop on the cropland in the area is soybeans, but corn, small grains, and cotton also are grown. Pastures are used mainly for beef production, but in some areas dairying is an important industry. About three-fourths of the forestland in the area is privately owned, and about one-fourth is owned by industry. The production of pond-raised catfish is important in west Alabama. Some areas are used for urban development.

The major soil resource concerns are water erosion, maintenance of the content of organic matter and productivity of the soils, and management of soil moisture. Water erosion and the infestation of Johnsongrass are major management concerns in cultivated areas. Conservation practices on cropland generally include systems of crop residue management, cover crops, crop rotations, water disposal, pest management, and nutrient management. The most important conservation practice on pasture is prescribed grazing. Pastures commonly are overseeded with small grains and/or legumes to supplement forage production during winter. Haying also helps to provide supplemental feed during the long winters. Critically eroding areas and areas where animals congregate should be monitored and treated.

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