Land use: Most of this MRLA is in farms. Urban use is inextensive but is expanding in a few places. Most of the farmland is used for pasture and range; some of the pasture was formerly cropped. About half is in improved grasses that are fertilized. Much of the rangeland has been overgrazed. The remaining acreage is in native and annual grasses. The cropland is used principally for grain sorghum, but cotton, corn, peanuts, hay, and truck crops are important in some places. About a third of the farmland is in woodlots.

Elevation and topography: Elevation ranges from 50 to 200 m. The Claypan Area is a nearly level to sloping plain. Dissected sites are steeper along entrenched river and creek valleys. Valleys of large streams are shallow, and the wide flood plains are bordered by nearly level terraces.

Climate: Average annual precipitation-750 to 1,075 mm. Maximum precipitation is in winter and in spring, and the minimum is in summer and in autumn. Average annual temperature-18 to 22 C, in- creasing from north to south. Average freeze-free period-240 to 280 days.

Water: The moderate precipitation is the major source of water for crops and pasture. Rainfall in summer is erratic, and in most years crop yields are reduced by a lack of moisture. A few large reservoirs on major streams provide municipal water and also serve as recreation facilities. Water for farm use comes from ponds and wells.

Soils: Most of the soils are Ustalfs. They are deep, medium textured and moderately coarse textured soils that have a slowly or very slowly permeable clayey subsoil. They have a thermic temperature regime, an ustic moisture regime, and montmorillonitic mineralogy. Moderately well drained, nearly level and gently sloping Paleustalfs (Axtell and Tabor series) and poorly drained Albaqualfs (Arol, Falba, and Lufkin series) are on the uplands. Interspersed in many places are well drained and moderately well drained Paleustalfs (Tremona, Catilla, Straber, Patilo, Padina, and Silstid series) that have a thick sandy surface. Pelluderts (Kaufman and Trinity series), Pellusterts (Burleson series), Haplustolls (Ships series), and Hapludolls (Pledger series) are on flood plains and clayey terraces along the Trinity and Brazos Rivers.

Potential natural vegetation: The climax plant community in this area is oak savanna. Little bluestem is dominant on all sites except those that are poorly drained. Little bluestem and beaked panicum are dominant in poorly drained areas. Indiangrass, brownseed paspalum, beaked panicum, switchgrass, and big bluestem grow throughout the area. The area also supports a wide variety of forbs, legumes, shrubs, and woody vines such as dayflower, spiderwort, bundleflower, lespedezas, sensitivebrier, hackberry, hawthorn, yaupon, elbowbush, greenbrier, and honeysuckle. Some mixed pine-hardwood forests are in the southwest and in the east. Hardwood forests of oak, elm, pecan, and other species grow on the wet bottom lands.

(From "Land Resource Regions and Major Land Resource Areas of the United States". United States Department of Agriculture Soil Conservation Service Handbook 296. Dec. 1981. page 63.)