Houston Black -- Texas State Soil

Photograph of landscape of Houston Black soil series.

Photograph of the profile of a typifying pedon of Houston Black soil series.

Houston Black Soil Profile

Surface layer:  black clay
Subsoil - upper:  black clay with slickensides
Subsoil - lower:  black clay with slickensides and calcium carbonate
Substratum:  light olive brown clay

The Houston Black series occurs on about 1.5 million acres in the Blackand Land Prairie, which extends from north of Dallas south to San Antonio. Because of their highly expansive clays, Houston Black soils are recognized throughout the world as the classic Vertisols, which shrink and swell markedly with changes in moisture content. These soils formed under prairie vegetation and in calcareous clays and marls. Water enters the soils rapidly when they are dry and cracked and very slowly when they are moist.

Houston Black soils are used extensively for grain sorghum, cotton, corn, small grain, and forage grasses. They also occur in several metropolitan areas, where their very high shrink-swell potential commonly is a limitation affecting building site development.

The Professional Soil Scientists Association of Texas has recommended to the State Legislature that the Houston Black series be designated the State soil. The series was established in 1902.

Small scale map of Texas showing distribution of Houston Black soil series.

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