LOCATION BRACKETT TX+OKEstablished Series
The Brackett series consists of very shallow to shallow soils over bedrock. These well drained and moderately permeable soils formed in residuum over chalky limestone bedrock mainly of the Glenrose formation of Cretaceous Age. These soils are on gently sloping to very steep uplands. Slopes range from 1 to 60 percent.
TAXONOMIC CLASS: Loamy, carbonatic, thermic, shallow Typic Haplustepts
TYPICAL PEDON: Brackett gravelly clay loam--rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 6 inches; grayish brown (10YR 5/2) gravelly clay loam, dark grayish brown (10YR 4/2) moist; moderate fine subangular blocky and granular structure; hard, friable; common fine roots; few masses and nodules of calcium carbonate; about 15 percent, by volume, weakly cemented limestone pebbles 2mm to 1 inch across; violently effervescent; moderately alkaline; clear smooth boundary. (3 to 12 inches thick)
Bw--6 to 14 inches; light gray (10YR 7/2) gravelly clay loam, light brownish gray (10YR 6/2) moist; moderate fine subangular blocky and granular structure; hard, friable; common fine roots; few masses and nodules of calcium carbonate; about 20 percent, by volume, weakly cemented limestone pebbles 2mm to 1 inch across; violently effervescent; moderately alkaline; clear wavy boundary. (3 to 16 inches thick)
Cr--14 to 60 inches; weakly cemented, fractured and weathered limestone bedrock with vertical fractures that roots can enter, 4 to 10 inches apart, interbedded with thin strata of pale yellow and very pale brown weathered chalk bedrock; moderately alkaline.
TYPE LOCATION: Hays County, Texas. From the intersection of Ranch Road 32 and Ranch Road 12 about 10 miles west of San Marcos, 6 miles west on Ranch Road 32 and 1,000 feet north of the road, in rangeland.
RANGE IN CHARACTERISTICS: The solum thickness over limestone bedrock ranges from 6 to 20 inches. Rock fragments above the paralithic contact average 0 to 35 percent by volume. Calcium carbonate equivalent ranges from 40 to about 85 percent in the fine-earth fraction and increases with depth. Reaction is slightly alkaline or moderately alkaline throughout. Carbonate clay content is 2 to 10 percent and silicate clay is 18 to 30 percent in the control section.
The A horizon has hue of 10YR or 2.5Y, value of 5 to 8, and chroma of 2 to 4. Texture is loam, clay loam, gravelly loam or gravelly clay loam. Where value is 5 the organic carbon content is less than 2.5 percent.
The Bw horizon has hue of 10YR or 2.5Y, value of 5 to 8, and chroma of 2 to 4. Yellowish and brownish mottles occur in the soil and within porous limestone fragments in some pedons. Texture is loam, clay loam, gravelly loam or gravelly clay loam. Secondary forms of calcium carbonate on fragments and within the soil ranges from few to common nodules, concretions, or masses.
In some pedons a Cr/Bk horizon is present that has the same colors as the Bk horizon in the fine earth fraction. The limestone bedrock in the Cr are mostly white or yellow but mottles or individual fragments may be, brownish or grayish in some pedons. The Cr is extremely weakly to moderately cemented chalk with weathered rinds of soft bedrock that slakes in water. The fine-earth fraction is loam or clay loam. Secondary forms of calcium carbonate on fragments and within the soil ranges from common to many nodules, concretions, or masses of calcium carbonate.
The Cr layer is extremely weakly to moderately cemented chalky limestone that is more than 6 inches thick with vertical fractures more than 4 inches apart horizontally. Most fractures are filled with secondary calcium carbonate.
COMPETING SERIES: These are no competing series in the same family. Similar soils include Doss and Whitewright. Doss soils have a typic ustic moisture regime and a mollic epipedon. Whitewright soils formed over the Austin Chalk.
GEOGRAPHIC SETTING: Brackett soils occur on undulating to hilly uplands. Slopes are mostly 1 to 20 percent but range from 1 to 60 percent. The soil formed in interbedded marl and limestone of the Lower Cretaceous age like the southern portion of the Glen Rose formation and Commanche Peak formations with some acreage on the Walnut and Keys Valley marl. The limestone in these areas weathers to a benched or stair stepped topography consisting of risers and treads. The Brackett soils are mainly on the treads. The mean annual precipitation ranges from about 26 to 32 inches, and mean annual air temperature ranges from 64 to 69 degrees F. Frost free days range from 210 to 270 days and elevation ranges from 600 to 2450 feet. Thorntwaite annual P.E. indices range from 32 to 52.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Cranfill, Denton, the Doss, Eckrant, Karnes, Maloterre, Real, Topsey, and Tarrant series. Denton soils occur at lower elevations, and do not have a paralithic contact within 20 inches of the surface. Doss soils are drier in the control section and have a mollic epipedon. Eckrant, Maloterre, and Tarrant soils occur at higher elevations, and are are clayey-skeletal. Real soils occur on similar surfaces and are loamy-skeletal. Cranfill, Karnes, and Topsey soils are deep and are very deep and are below or on slightly lower positions.
DRAINAGE AND PERMEABILITY: Well drained. Runoff is very low on 1 to 3 percent slopes, low on 3 to 5 percent slopes, medium on 5 to 20 percent slopes and high on 20 to 60 percent slopes. Permeability is moderate.
USE AND VEGETATION: Mainly used for livestock grazing and wildlife habitat. Original vegetation was rolling prairies dominated by little bluestem, indiangrass, and grama species. Woody vegetation includes juniper, sumac, liveoak, Vasey Oak, and Texas oak. Most of these plants can still be observed on these soils. In many places extended periods of overgrazing allows plants such as Texas grama, red grama, hairy tridens, and juniper to replace plants more desired by livestock.
DISTRIBUTION AND EXTENT: Eastern Edwards Plateau and Grand Prairie Land Resource areas of southwest and central and north-central Texas. The series is extensive.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Kinney County, Texas (Reconnaissance Soil Survey of Southwest Texas); 1911.
REMARKS: Classification was changed 11/89 from Typic Ustochrepts to Udic Ustochrepts. On 10/2001 the type location was moved to Hays County, and the depth was changed from very deep to shallow and the sugroup changed back to Typic which was the original series concept.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipdeon - 0 to 7 inches after mixing (A and Bw)
Cambic horizon - 6 to 14 inches (Bk)
Paralithic contact - at 14 inches (top of Cr)
Ecological Sites: 1 to 20 percent slopes, Adobe PE 31-44 (081BY320TX), Adobe PE 44+(081CY355TX); and 20 to 60 percent slopes, Steep Adobe PE 31-44 (081BY348TX), Steep Adobe PE 44+ (081CY362TX).
ADDITIONAL DATA:
TAXONOMIC VERSION: Soil Taxonomy, Second Edition, 1999.