Land use: Nearly all this area is in farms and ranches. About 40 percent is rangeland, 30 percent woodland, 15 percent pastureland, and almost 15 percent cropland. The rest is used for urban development and for other purposes. All the rangeland, woodland, and pastureland is grazed by beef cattle, but locally there are some dairy cattle. Small grains, grain sorghum, cotton, alfalfa, and other hay crops are important in much of the area. Large acreages of peanuts, tree fruits, and vegetables are grown in the south.
Elevation and topography: Elevation ranges from 300 to 400 m, but along the Red River it is 200 m. Ridgetops on these rolling to hilly uplands are nearly level to strongly rolling and narrow to moderately broad. Stream valleys are narrow and have steep gradients. Local relief is mostly a few tens of meters, but the large valleys are 50 m or more below the adjacent uplands.
Climate: Average annual precipitation - 625 mm in the west to 900 mm in the east. Maximum precipitation is in spring, and the minimum is in winter. Snowfall ranges from 30 cm in the north to 10 cm in the south. Average annual temperature - 15 to 17 C. Average freeze-free period - 190 to 240 days.
Water: The moderate and somewhat erratic rainfall is the source of water for range and crops. Large reservoirs provide water for cities and towns and for recreation or flood control. Farm ponds are a major source of water for livestock. In most of the area, shallow wells supply water for domestic use, but ground water is scarce in places where sandstone and shale are near the surface.
Soils: The major soils are Ustalfs and Ochrepts. They have a thermic temperature regime and an ustic moisture regime. The Ustalfs are loamy and have a loamy or clayey subsoil and siliceous or mixed mineralogy. Well drained, very gently sloping, undulating to sloping or hummocky, moderately deep to deep Haplustalfs (Dougherty, Konawa, Stephenville, and Weatherford series) are on uplands. Well drained and moderately well drained, very gently sloping to steep or rolling, deep Paleustalfs (Chaney, Demona, Duffau, Eufaula, Nimrod, Niotaze, and Windthorst series) are on uplands. Ochrepts are shallow and loamy and have siliceous mineralogy. Well drained to somewhat excessively drained, very gently sloping, shallow Ustochrepts (Darnell series) are on ridge crests and steep valley slopes. Well drained, deep, nearly level Ustifluvents (Bunyan, Pulaski, and Pulexas series) and somewhat poorly drained, nearly level, deep Udifluvents (Tribbey series) are on flood plains.
Potential natural vegetation: This area supports an open stand of trees with an understory of mid and tall grasses, forbs, and low woody plants. Post oak and blackjack oak are the dominant tree species. Big bluestem, little bluestem, indiangrass, sunflower, and lespedezas are the major species in the herbaceous understory.
(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 60.)