LOCATION STAMFORD TX+OKEstablished Series
The Stamford series consists of moderately deep, well drained, very slowly permeable soils formed in reddish calcareous clay. These soils are on nearly level and gently sloping uplands. Slopes range from 0 to 5 percent.
TAXONOMIC CLASS: Fine, smectitic, thermic Chromic Haplusterts
TYPICAL PEDON: Stamford clay--pasture.
(Colors are for dry soil unless otherwise stated.)
A--0 to 9 inches; reddish brown (2.5YR 4/4) clay, dark reddish brown (2.5YR 3/4) moist; moderate fine and very fine blocky structure; very hard, very firm, very sticky, plastic; surface mulch of very hard, fine peds; few fine roots; few fine pores; few wormcasts; calcareous; moderately alkaline; gradual wavy boundary. (6 to 30 inches thick)
AC--9 to 35 inches; red (2.5YR 4/5) clay, dark red (2.5YR 3/5) moist; moderate medium angular blocky structure; extremely hard, very firm, sticky, plastic; few fine roots and very fine pores; below 50 cm many parallelepipeds have the long axes tilted about 30 degrees from the horizontal; few prominent intersecting slickensides; few concretions of calcium carbonate about 2 to 5 mm in diameter; calcareous; moderately alkaline; gradual smooth boundary. (20 to 36 inches thick)
Cd--35 to 60 inches; clay, dark red (10R 3/6) moist; massive; extremely hard, very firm, sticky, plastic; some thin strata of light gray clay; calcareous; moderately alkaline.
TYPE LOCATION: Runnels County, Texas; from the courthouse in Ballinger, 12.5 miles southwest on U.S. Highway 67, then 4.2 miles north and 0.5 mile west on county roads, then 100 feet north in rangeland.
RANGE IN CHARACTERISTICS: Depth of the solum to the Cd horizon ranges from 28 to 54 inches. The soil surface, where undisturbed, has galgai microrelief, the soil has cracks more than 1 cm wide at a depth of 50 cm and the cracks remain open for more than 150 cumulative days during most years. The clay is dominantly montmorillonite. The control section ranges from 40 to 60 percent clay. Thickness of the A horizon, within the limits of a pedon, ranges from 6 to 20 inches.
The A horizon is reddish gray (5YR 5/2), dark reddish gray (5YR 4/2), or reddish brown (5YR 5/3, 5/4, 4/3, 4/4; 2.5YR 5/4, 4/4). Where the A horizon is less than 12 inches thick, dry value is less than 5.5 and moist value less than 3.5 to depths of more than 12 inches in more than half of the pedon.
The AC horizon is reddish brown (5YR 5/3, 4/3, 5/4, 4/4; 2.5YR 5/4, 4/4), weak red (10R 5/4, 4/4), or red (2.5YR 5/6), 4/6; 10R 5/6, 4/6). Carbonates in this horizon vary from a few visible films and threads to 5 or 10 percent soft bodies and weakly cemented concretions.
The Cd horizon is weak red, red, or reddish brown in hues 10R, 2.5YR and 5YR. Some pedons have a Cr layer that ranges from massive unaltered clayey shale to partially weathered clayey or silty redbeds. Thin strata of sandstone, shale, or dolomitic limestone occur below 40 inches in some pedons.
COMPETING SERIES: These are the Bonita, Leeray, Rimrock, and Tobosa series in the same family and the Crawford, Dalby, Harlingen, Lela, Mangum, Montoya, Tillman, and Vernon soils in similar families. Bonita, Dalby, Montoya, and Rimrock soils are drier in the control section for longer periods of time; and in addition, Bonita soils have coarse fragments in the surface layer and buried argillic horizons; Harlingen soils have mean annual soil temperatures more than 72 degrees F.; and the Rimrock soils are underlain by bedrock at 20 to 40 inches depth. Leeray soils are of 7.5YR or 10YR hue in the A horizon. Lela soils have cracks that remain open for less than 90 cumulic days during most years. Mangum soils lack gilgai microrelief and intersecting slickensides. Montoya and Vernon soils have mixed mineralogy; and in addition, Vernon soils lack cracks l cm wide at a depth of 50 cm. Tillman soils have loamy A horizons and Bt horizons. Tobosa soils have A horizons of 7.5YR through 2.5Y hue.
GEOGRAPHIC SETTING: Stamford soils are on plane, concave, and convex surfaces of uplands. Slopes are 0 to 5 percent. The soil formed in reddish calcareous clay, generally several feet thick, but other materials are below 40 inches in some places. The climate is semiarid to dry subhumid. Average annual precipitation ranges from 17 to 28 inches. Thornthwaite annual P-E indices from 24 to 44, mean annual air temperature from 58 to 68 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Tillman and Vernon series, and Hollister and Wichita series. Hollister and Wichita soils have argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; very slow permeability. Water enters the soil rapidly through cracks when the soil is dry, but very slowly when the soil is wet.
USE AND VEGETATION: Mostly in native range, but some is cropped to small grains and sorghums. Short grasses, mainly tobosa and buffalograss, are dominant and some curly mesquite and various woody plants such as mesquite and lote bush, and some tasajillo and pricklypear.
DISTRIBUTION AND EXTENT: Mainly in the western parts of the Rolling Red Plains of Texas and western Oklahoma. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Harmon County, Oklahoma; 1941.
REMARKS: Stamford series was formerly classified in the Grumusol great soil group. The Stamford correlated in the Aridic Ustic moisture regime area over the Triassic Redbeds is moderately deep and has more sodium.