Land use: Most of this area is range grazed by beef cattle and wildlife. Grain sorghum, small grain, cotton, and improved pasture are the principal crops. Small grain is mostly grazed for winter pasture. Hunting leases for deer, quail, mourning dove, wild turkey, and javelina are an important source of income. The major concern of management is controlling brush and cactus that invade the native grasslands. Locally, saline and alkali soils are a land use problem.
Elevation and topography: Elevation ranges from 50 m in the southeast to 300 m in the northwest. Much of this plain is gently undulating and somewhat dissected by intermittent drainageways.
Climate: Average annual precipitation-425 to 525 mm. Maximum precipitation is during the growing season. Average annual temperature-21 to 22 C. Average freeze-free period-260 to 290 days.
Water: Rainfall is adequate for the growth of range grasses. In most years it is inadequate for cropland because of saline soils, high temperatures, and high evaporation and transpiration rates. The Rio Grande is the major perennial stream; other rivers flow intermittently. Locally, deep wells and ponds provide water for livestock, domestic use, and irrigation.
Soils: Most of the soils are Usterts and Torrerts. They are deep, fine textured saline soils that have montmorillonitic mineralogy. Also extensive are Ustolls and Orthids that have been mixed mineralogy. These soils have a hyperthermic temperature regime and an ustic or aridic moisture regime. Nearly level to gently sloping Pellusterts (Montell and Monteola series) are on plains over clayey marine sediments. Gently undulating Torrerts (Catarina series) are on plains in the southwestern part of the area. Nearly level Haplustolls (Dant series) and Calciustolls (Elindio series) are on broad plains in the northern part. Shallow and gravelly Calciustolls (Jimenez and Olmos series) are on ridges and small hills. Nearly level to gently undulating Calciorthids (Copita and Pryor series) are on plains over marine sediments.
Potential natural vegetation: This area supports open grassland with
scattered shrubs. Mid grasses such as alkali sacaton, twoflower trichloris,
pink pappusgrass, white tridens, whiplash pappusgrass, and vine-mesquite
are dominant on deep, clayey soils. Guayacan, spiny hackberry, desert yaupon,
and fourwing saltbush are the principal shrubs. Bundleflower, bushsunflower,
Texas varilla, and other forbs make up a minor but significant part of the
plant communities. The more gravelly soils support semiopen grassland vegetation
of mid grasses interspersed with low-growing shrubs. Guajillo, blackbrush,
and kidneywood are the principal shrubs. Arizona cottontop, sideoats grama,
pink pappusgrass, pinhole bluestem, green sprangletop, and tanglehead are
the dominant grasses. Several species of forbs grow on these soils, mainly
bushsunflower, orange zexmania, snoutbeans, daleas, and gauras.
(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. pages 57 - 58.)