Region 4: The Great Plains

The most common soils in the Great Plains area are Mollisols, which are widespread throughout the region. These loamy soils are well-drained and permeable, containing ample organic matter and a high nutrient content (see Figure 8.16). Most Great Plains Mollisols have been cultivated for use as farmland. In a portion of West Texas, they occur above igneous parent material, but they otherwise occur atop a variety of geologic substrates. In the Mollisols of Texas, carbonate minerals and salts leaching from upper layers of the soil often accumulate to such a degree that they form a cemented soil horizon called caliche.

Alfisols in the Great Plains are mostly limited to drier and slightly higher-elevation plateaus of northern Texas, such as the Llano Estacado, where they are interspersed with Mollisols. Aridisols occur in the lower-elevation portions of this area, especially around the border with southeastern New Mexico. Entisols are very limited in extent, occurring mostly along the Canadian and Pecos rivers. Inceptisols are likewise limited and are found only in the northernmost parts of Texas in the Great Plains region. Vertisols are limited to a small area in western Texas.