The Coastal Prairies

R. K. Walker and R. J. Miears.

The Coastal Prairie region in southwestern Louisiana and in southeastern Texas includes about 8 million acres. It almost parallels the coast of the Gulf of Mexico. A long, narrow band of coastal marshland lies between the prairie and the gulf.

The climate is subtropical. The average annual rainfall ranges from 58 inches in Louisiana to 34 inches in Texas. The average January temperature is 55 F. The average July temperature is 83 F. The average number of days between the last frost in spring and first frost in fall is 286. Extremely hot weather and severe cold weather seldom occur.

THE TOPOGRAPHY appears to be flat over wide areas, but the land slopes gradually to the gulf. The maximum elevation above sea level is slightly more than 100 feet, but most of the area is less than 50 feet above sea level. The prairie is bisected by many small streams and several large, well-defined streams with pronounced and fairly steep bordering slopes. Pimple mounds are conspicuous in several places.

The soils were formed from material carried by fresh water to the sea and deposited. These sediments were later uplifted and subjected to soil-forming processes under a grass cover.

The principal soils in Louisiana (and also in extensive sections in Texas) are deep, medium in texture, and slowly permeable. Crowley, Beaumont, and Midland soils are the major series. The top to inches is a friable, light-brown silt loam, which becomes light gray when it dries thoroughly. The next 10 to 18 inches is a smooth, floury silt loam, which grades sharply into mottled yellow, red, and gray, heavy, plastic silty clay or clay. The thickness of the surface soil layer and the depth of subsoil vary considerably.

The large areas of deep, fine-textured, slowly permeable soils lie mainly in Texas. Lake Charles, Edna, and Beaumont are the major soil series. This group of soils is characterized by heavy, dense clay, with little difference between the topsoil and subsoil. The soils are sticky when wet but become slightly granular when dry. The surface soils are dark gray to black.

Extensive areas of deep, fine-textured, slowly permeable soils with dark-gray loam to clay surface soils also exist in the Coastal Prairie. They are sticky when wet but granular and crumbly when dry.

Approximately 2.5 percent of the region is composed of bottom land. About 90 percent of the Louisiana Coastal Prairie region is in cultivation. Only 25 percent of the Texas region is cultivated.

Rice production dominates the Louisiana and eastern Texas part of the Coastal Prairie.

In the extreme western part in Texas, the main crops are cotton, grain sorghums, and corn. Some rice is grown there also.

Cattle are raised in conjunction with the major crops. Approximately 75 percent of the Texas Coastal Prairie is in pasture. Vegetable crops and dairying are important in small areas near cities.

The general cropping system in the part where rice is the dominant crop is 1 year in rice and 2 years or more in native grass pasture. No definite cropping system is used over large areas in the western end of the region, but cotton generally is rotated with corn and grain sorghum, and winter legumes are grown in some localities in rotation with row crops.

The principal soil problems are poor drainage, both surface and internal; poor physical condition of soils; a low content of organic matter; and a relatively low fertility level. Lack of available nitrogen and phosphorus is the major deficiency.

SURFACE DRAINAGE of large portions of various watersheds was the dominant soil-management problem when the land was originally put into cultivation. Much emphasis has been placed on improvement of drainage of these areas by Federal, State, and local agencies. Some drainage projects have been completed. Others were in varying stages of completion in 1957, and much remained to be done to provide proper drainage of the entire area.

Individual farm drainage has been vastly improved by providing drainage ditches. Field drainage has been greatly improved by land-leveling practices. Conservation of irrigation water in flooding riceland is another result of land leveling, which has been done on an extensive scale and is a standard practice.

Poor internal drainage of the Coastal Prairie soils is an inherent characteristic that cannot be altered very much. This factor is favorable for keeping ricelands under a continuous flood during the growing season, but it prohibits the successful production of a large number of crops and makes the soil difficult to work for good seedbed preparation and cultivation.

A trend toward a rotation of improved pastures and rice has been evident in the Coastal Prairie rice area.

Results of longtime experimental work in Louisiana show that rotation of improved pastures with rice will increase beef production from 46 to 271 pounds an acre annually and increase rice yields by 5 barrels an acre. The rotation also combats undesirable grasses, broad-leaved weeds, and "red rice," increases the fertility level of the soil, and improves its physical condition.

Improved pastures that may contain ryegrass, whiteclover, Dallisgrass, Bermuda-grass, and lespedeza, supplemented with oats or wheat for temporary winter grazing and with lespedeza or alyceclover for temporary summer grazing and hay production, provide high-quality grazing, hay, and grain in the area.

A NEED exists for supplementary irrigation of nearly all crops in the region, even though the annual rainfall is relatively high.