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and TDD). To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326W, Whitten Building, 14th and Independence Avenue, SW,
Washington, DC 20250-9410 or call 202-720-5964 (voice or TDD). USDA is an equal opportunity provider and employer.
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 Blackland 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.
HOUSTON BLACK -- TEXAS STATE SOIL
