Soils of Texas
One of Texas’ most important natural resources is its soil. Texas soils are complex because of the wide diversity of climate, vegetation, geology, and landscape. More than 1,300 different kinds of soil are recognized in Texas. Each has a specific set of properties that affect its use.
Major Soil Areas
Texas can be divided into 21 Major Land Resource Areas that have similar or related soils, vegetation, topography, climate, and land uses. Following are brief descriptions of these areas:
The 18.7 million acres of the Trans-Pecos, mostly west of the Pecos River, are diverse plains and valleys intermixed with mountains. Surface drainage is slow to rapid. This arid region is used mainly as rangeland. A small amount of irrigated cropland lies on the more fertile soils along the Rio Grande and the Pecos River. Vineyards are a more recent use of these soils, as is the disposal of large volumes of municipal wastes.
Upland soils are mostly well-drained, light reddish-brown to brown clay loams, clays, and sands (some have a large amount of gypsum or other salts). Many areas have shallow soils and rock outcrops, and sizable areas have deep sands. Bottomland soils are deep, well-drained, dark grayish-brown to reddish-brown silt loams, loams, clay loams, and clays. The lack of soil moisture and wind erosion are the major soil-management problems. Only irrigated crops can be grown on these soils, and most areas lack an adequate source of good water.
Upper Pecos, Canadian Valleys, and Plains Soils
The Upper Pecos, Canadian Valleys, and Plains area occupies a little over a half-million acres and is in the northwest part of Texas near the Texas–New Mexico border. It is characterized by broad rolling plains and tablelands broken by drainageways and tributaries of the Canadian River. It includes the Canadian Breaks, which are rough, steep lands below the adjacent High Plains. The average annual precipitation is about 15 inches, but it fluctuates widely from year to year. Surface drainage is slow to rapid.
The soils are well drained and alkaline. The mostly reddish-brown clay loams and sandy loams were formed mostly in material weathered from sandstone and shale. Depths range from shallow to very deep.
The area is used mainly as rangeland and wildlife habitat. Native vegetation is mid- to short-grass prairie species, such as hairy grama, sideoats grama, little bluestem, alkali sacaton, vine-mesquite, and galleta in the plains and tablelands. Juniper and mesquite grow on the relatively higher breaks. Soil management problems include low soil moisture and brush control.
High Plains Soils
The High Plains area comprises a vast high plateau of more than 19.4 million acres in northwestern Texas. It lies in the southern part of the Great Plains province that includes large, similar areas in Oklahoma and New Mexico. The flat, nearly level treeless plain has few streams to cause local relief. However, several major rivers originate in the High Plains or cross the area. The largest is the Canadian River, which has cut a deep valley across the Panhandle section.
Playas, small intermittent lakes scattered through the area, lie up to 20 feet below the surrounding plains. A 1965 survey counted more than 19,000 playas in 44 counties occupying some 340,000 acres. Most runoff from rainfall is collected in the playas, but only 10 to 40 percent of this water percolates back to the Ogallala Aquifer. The aquifer is virtually the exclusive water source in this area.
Upland soils are mostly well-drained, deep, neutral to alkaline clay loams and sandy loams in shades of brown or red. Sandy soils are in the southern part. Many soils have large amounts of lime at various depths and some are shallow over caliche. Soils of bottomlands are minor in extent.
The area is used mostly for cropland, but significant areas of rangeland are in the southwestern and extreme northern parts. Millions of cattle populate the many large feedlots in the area. The soils are moderately productive, and the flat surface encourages irrigation and mechanization. Limited soil moisture, constant danger of wind erosion, and irrigation water management are the major soil-management problems, but the region is Texas’ leading producer of three important crops: cotton, grain sorghums, and wheat.
Rolling Plains Soils
The Rolling Plains include 21.7 million acres east of the High Plains in northwestern Texas. The area lies west of the North Central Prairies and extends from the edge of the Edwards Plateau in Tom Green County northward into Oklahoma. The landscape is nearly level to strongly rolling, and surface drainage is moderate to rapid. Outcrops of red beds, geologic materials, and associated reddish soils have led some scientists to use the name “Red Plains.” Limestone underlies the soils in the southeastern part. The eastern part contains large areas of badlands.
Upland soils are mostly deep, pale-brown through reddish-brown to dark grayish-brown, neutral to alkaline sandy loams, clay loams, and clays; some are deep sands.
Many soils have a large amount of lime in the lower part, and a few others are saline; some are shallow and stony. Bottomland soils are mostly reddish-brown and sandy to clayey; some are saline.
This area is used mostly for rangeland, but cotton, grain sorghums, and wheat are important crops. The major soil-management problems are brush control, wind erosion, low fertility, and lack of soil mosture. Salt spots are a concern in some areas.
North Central Prairie Soils
The North Central Prairie occupies about 7 million acres in North Central Texas. Adjacent to this area on the north is the rather small area (less than 1 million acres) called Rolling Red Prairies, which extends into Oklahoma and is included here because the soils and land use are similar. This area lies between the Western Cross Timbers and the Rolling Plains. It is predominantly grassland intermixed with small wooded areas. The landscape is undulating with slow to rapid surface drainage.
Upland soils are mostly deep, well-drained, brown or reddish-brown, slightly acid loams over neutral to alkaline, clayey subsoils. Some soils are shallow or moderately deep to shale. Bottomland soils are mostly well-drained, dark-brown or gray loams and clays.
This area is used mostly as rangeland, but wheat, grain sorghums, and other crops are grown on the better soils. Brush control, wind and water erosion, and limited soil moisture are the major management concerns.
Edwards Plateau Soils
The 22.7 million acres of the Edwards Plateau are in South Central Texas east of the Trans-Pecos and west of the Blackland Prairie. Uplands are nearly level to undulating except near large stream valleys, where the landscape is hilly with deep canyons and steep slopes. There are many cedar brakes in this area. Surface drainage is rapid.
Upland soils are mostly shallow, stony, or gravelly, dark alkaline clays and clay loams underlain by limestone. Lighter-colored soils are on steep sideslopes and deep, less-stony soils are in the valleys. Bottomland soils are mostly deep, dark-gray or brown, alkaline loams and clays.
Raising beef cattle is the main enterprise in this region, but it is also the center of Texas’ and the nation’s mohair and wool production. The area is a major deer habitat, and hunting leases produce income. Cropland is mostly in the valleys on the deeper soils and is used mainly for growing forage crops and hay. The major soil-management concerns are brush control, large stones, low fertility, excess lime, and limited soil moisture.
Central or Llano Basin Soils
The Central Basin, also known as the Llano Basin, occupies a relatively small area in Central Texas. It includes parts or all of Llano, Mason, Gillespie, and adjoining counties. The total area is about 1.6 million acres of undulating to hilly landscape.
Upland soils are mostly shallow, reddish-brown to brown, mostly gravelly and stony, neutral to slightly acid sandy loams over granite, limestone, gneiss, and schist bedrock. Large boulders are on the soil surface in some areas. Deeper, less stony sandy-loam soils are in the valleys. Bottomland soils are minor areas of deep, dark-gray or brown loams and clays.
Ranching is the main enterprise, with some farms producing peaches, grain sorghum, and wheat. The area provides excellent deer habitat, and hunting leases are a major source of income. Brush control, large stones, and limited soil moisture are soil-management concerns.
Northern Rio Grande Plain Soils
The Northern Rio Grande Plain comprises about 6.3 million acres in South Texas extending from Uvalde to Beeville. The landscape is nearly level to rolling, mostly brush-covered plains with slow to rapid surface drainage.
The major upland soils are deep, reddish-brown or dark grayish-brown, neutral to alkaline loams and clays. Bottomland soils are mostly dark-colored loams.
The area is mostly rangeland with significant areas of cropland. Grain sorghums, cotton, corn, and small grains are the major crops. Crops are irrigated in the western part, especially in the Winter Garden area, where vegetables such as spinach, carrots, and cabbage are grown. Much of the area is good deer and dove habitat; hunting leases are a major source of income. Brush control, soil fertility, and irrigation-water management are the major soil-management concerns.
Western Rio Grande Plain Soils
The Western Rio Grande Plain comprises about 5.3 million acres in an area of southwestern Texas from Del Rio to Rio Grande City. The landscape is nearly level to undulating except near the Rio Grande where it is hilly. Surface drainage is slow to rapid.
The major soils are mostly deep, brown or gray alkaline clays and loams. Some are saline.
Most of the soils are used for rangeland. Irrigated grain sorghums and vegetables are grown along the Rio Grande. Hunting leases are a major source of income. Brush control and limited soil moisture are the major soil-management problems.
Central Rio Grande Plain Soils
The Central Rio Grande Plain comprises about 5.9 million acres in an area of South Texas from Live Oak County to Hidalgo County. It Includes the South Texas Sand Sheet, an area of deep, sandy soils and active sand dunes. The landscape is nearly level to gently undulating. Surface drainage is slow to rapid. Upland soils are mostly deep, light-colored, neutral to alkaline sands and loams. Many are saline or sodic. Bottomland soils are of minor extent.
Most of the area is used for raising beef cattle. A few areas, mostly in the northeast part, are used for growing grain sorghums, cotton, and small grains. Hunting leases are a major source of income. Brush control is the major soil-management problem on rangeland; wind erosion and limited soil moisture are major concerns on cropland.
Lower Rio Grande Valley Soils
The Lower Rio Grande Valley comprises about 2.1 million acres in extreme southern Texas. The landscape is level to gently sloping with slow surface drainage.
Upland soils are mostly deep, grayish-brown, neutral to alkaline loams; coastal areas are mostly gray, silty clay loam and silty clay; some are saline. Bottomland soils are minor in extent.
Most of the soils are used for growing irrigated vegetables and citrus, along with cotton, grain sorghums, and sugar cane. Some areas are used for growing beef cattle. Irrigation water management and wind erosion are the major soil-management problems on cropland; brush control is the major problem on rangeland.
Western Cross Timbers Soils
The Western Cross Timbers area comprises about 2.6 million acres. It includes the wooded section west of the Grand Prairie and extends from the Red River southward to the north edge of Brown County. The landscape is undulating and is dissected by many drainageways including the Brazos and Red rivers. Surface drainage is rapid.
Upland soils are mostly deep, grayish-brown, slightly acid loams with loamy and clayey subsoils. Bottomland soils along the major rivers are deep, reddish-brown, neutral to alkaline silt loams and clays.
The area is used mostly for grazing beef and dairy cattle on native range and improved pastures. Crops are peanuts, grain sorghums, small grains, peaches, pecans, and vegetables. The major soil-management problem on grazing lands is brush control. Waste management on dairy farms is a more recent concern. Wind and water erosion are the major problems on cropland.
Eastern Cross Timbers Soils
The Eastern Cross Timbers area comprises about 1 million acres in a long narrow strip of wooded land that separates the northern parts of the Blackland Prairie and Grand Prairie and extends from the Red River southward to Hill County. The landscape is gently undulating to rolling and is dissected by many streams, including the Red and Trinity rivers. Sandstone-capped hills are prominent in some areas. Surface runoff is moderate to rapid.
The upland soils are mostly deep, light-colored, slightly acid sandy loams and loamy sands with reddish loamy or clayey subsoils. Bottomland soils are reddish-brown to dark gray, slightly acid to alkaline loams or gray clays.
Grassland consisting of native range and improved pastures is the major land use. Peanuts, grain sorghums, small grains, peaches, pecans, and vegetables are grown in some areas. Brush control, water erosion, and low fertility are the major soil concerns in management.
Grand Prairie Soils
The Grand Prairie comprises about 6.3 million acres in North Central Texas. It extends from the Red River to about the Colorado River. It lies between the Eastern and Western Cross Timbers in the northern part and just west of the Blackland Prairie in the southern part. The landscape is undulating to hilly and is dissected by many streams including the Red, Trinity, and Brazos rivers. Surface drainage is rapid.
Upland soils are mostly dark-gray, alkaline clays; some are shallow over limestone and some are stony. Some areas have light-colored loamy soils over chalky limestone. Bottomland soils along the Red and Brazos rivers are reddish silt loams and clays. Other bottomlands have dark-gray loams and clays.
Land use is a mixture of rangeland, pastureland, and cropland. The area is mainly used for growing beef cattle. Some small grain, grain sorghums, corn, and hay are grown. Brush control and water erosion are the major management concerns.
Blackland Prairie Soils
The Blackland Prairies consist of about 12.6 million acres of east-central Texas extending southwesterly from the Red River to Bexar County. There are smaller areas to the southeast. The landscape is undulating with few scattered wooded areas that are mostly in the bottomlands. Surface drainage is moderate to rapid.
Both upland and bottomland soils are deep, dark-gray to black alkaline clays. Some soils in the western part are shallow to moderately deep over chalk. Some soils on the eastern edge are neutral to slightly acid, grayish clays and loams over mottled clay subsoils (sometimes called graylands). Blackland soils are known as “cracking clays” because of the large, deep cracks that form in dry weather. This high shrink-swell property can cause serious damage to foundations, highways, and other structures and is a safety hazard in pits and trenches.
Land use is divided about equally between cropland and grassland. Cotton, grain sorghums, corn, wheat, oats, and hay are grown. Grassland is mostly improved pastures, with native range on the shallower and steeper soils. Water erosion, cotton root rot, soil tilth, and brush control are the major management problems.
Claypan Area Soils
The Claypan Area consists of about 6.1 million acres in east-central Texas just east of the Blackland Prairie. The landscape is a gently undulating to rolling, moderately dissected woodland also known as the Post Oak Belt or Post Oak Savannah. Surface drainage is moderate.
Upland soils commonly have a thin, light-colored, acid sandy loam surface layer over dense, mottled red, yellow, and gray claypan subsoils. Some deep, sandy soils with less clayey subsoils exist. Bottomlands are deep, highly fertile, reddish-brown to dark-gray loamy to clayey soils.
Land use is mainly rangeland. Some areas are in improved pastures. Most cropland is in bottomlands that are protected from flooding. Major crops are cotton, grain sorghums, corn, hay, and forage crops, most of which are irrigated. Brush control on rangeland and irrigation water management on cropland are the major soil-management problems. Water erosion is a serious problem on the highly erosive claypan soils, especially where they are overgrazed.
East Texas Timberland Soils
The East Texas Timberlands area comprises about 16.1 million acres of the forested eastern part of the state. The land is gently undulating to hilly and well dissected by many streams. Surface drainage is moderate to rapid.
This area has many kinds of upland soils but most are deep, light-colored, acid sands and loams over loamy and clayey subsoils. Deep sands are in scattered areas, and red clays are in areas of “redlands.” Bottomland soils are mostly brown to dark-gray, acid loams and some clays.
The land is used mostly for growing commercial pine timber and for woodland grazing. Improved pastures are scattered throughout and are used for grazing beef and dairy cattle and for hay production. Some commercial hardwoods are in the bottomlands. Woodland management problems include seedling survival, invasion of hardwoods in pine stands, effects of logging on water quality, and control of the southern pine beetle. Lime and fertilizers are necessary for productive cropland and pastures.
Coast Prairie Soils
The Coast Prairie includes about 8.7 million acres near the Gulf Coast. It ranges from 30 miles to 80 miles in width and parallels the coast from the Sabine River in Orange County in Southeast Texas to Baffin Bay in Kleberg County in South Texas. The landscape is level to gently undulating with slow surface drainage.
Upland soils are mostly deep, dark-gray, neutral to slightly acid clay loams and clays. Lighter-colored and more-sandy soils are in a strip on the northwestern edge. Some soils in the southern part are alkaline; some are saline and sodic. Bottomland soils are mostly deep, dark-colored clays and loams along small streams but are greatly varied along the rivers.
Land use is mainly grazing lands and cropland. Some hardwood timber is in the bottomlands. Many areas are also managed for wetland wildlife habitat. The nearly level topography and productive soils encourage farming. Rice, grain sorghums, cotton, corn, and hay are the main crops. Brush management on grasslands and removal of excess water on cropland are the major management concerns.
Coast Saline Prairies Soils
The Coast Saline Prairies area includes about 3.2 million acres along a narrow strip of wet lowlands adjacent to the coast; it includes the barrier islands that extend from Mexico to Louisiana. The surface is at or only a few feet above sea level with many areas of salt-water marsh. Surface drainage is very slow.
The soils are mostly deep, dark-colored clays and loams; many are saline and sodic. Light-colored sandy soils are on the barrier islands. The water table is at or near the surface of most soils.
Cattle grazing is the chief economic use of the various salt-tolerant cordgrasses and sedges. Many areas are managed for wetland wildlife. Recreation is popular on the barrier islands. Providing fresh water and access to grazing areas are the major management concerns.
Gulf Coast Marsh Soils
This 150,000-acre area lies in the extreme southeastern corner of Texas. The area can be subdivided into four parts: freshwater, intermediate, brackish, and saline (saltwater) marsh. The degree of salinity of this system grades landward from saltwater marshes along the coast to freshwater marshes inland. Surface drainage is very slow.
This area contains many lakes, bayous, tidal channels, and man-made canals. About one-half of the marsh is fresh; one-half is salty. Most of it is susceptible to flooding either by fresh water drained from lands adjacent to the marsh or by saltwater from the Gulf of Mexico. Most of the soils are poorly drained, continuously saturated, soft, and can carry little weight. In general, the organic soils have a thick layer of dark gray, relatively undecomposed organic material over a gray, clayey subsoil. The mineral soils have a surface of dark gray, highly decomposed organic material over a gray, clayey subsoil.
Most of the almost treeless and uninhabited area is in marsh vegetation, such as grasses, sedges, and rushes. It is used mainly for wildlife habitat. Part of the fertile and productive estuarine complex supports marine life of the Gulf of Mexico. It also provides wintering ground for waterfowl and habitat for many fur-bearing animals and alligators. A significant acreage is firm enough to support livestock and is used for winter grazing of cattle. The major management problems are providing fresh water and access to grazing areas.
The Flatwoods area includes about 2.5 million acres of woodland in humid Southeast Texas just north of the Coast Prairie and extending into Louisiana. The landscape is level to gently undulating. Surface drainage is slow.
Upland soils are mostly deep, light-colored, acid loams with gray, loamy, or clayey subsoils. Bottomland soils are deep, dark-colored, acid clays and loams. The water table is near the surface at least part of the year.
The land is mainly used for forest, although cattle are grazed in some areas. Woodland management problems include seedling survival, invasion of hardwoods in pine stands, effects of logging on water quality, and control of the southern pine beetle.
Source: Natural Resources Conservation Service, U.S. Department of Agriculture.
Soil maps and information about soils and their uses are available for nearly all of the state’s 254 counties. Texas’ official soil information site is the the Web Soil Survey: websoilsurvey.nrcs.usda.gov.
For more information, contact the Natural Resources Conservation Service at 101 S. Main, Temple 76501-7602; (254) 742-9800; or visit www.tx.nrcs.usda.gov; click on “Information About: Soils.”