LOCATION ALTOGA TXEstablished Series
TAXONOMIC CLASS: Fine-silty, carbonatic, thermic Udic Haplustepts
TYPICAL PEDON: Altoga silty clay - cultivated. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 7 inches; light brownish gray (10YR 6/2) silty clay, grayish brown (10YR 5/2) moist; strong very fine subangular blocky and granular structure; slightly hard, friable; few fine roots; calcareous; moderately alkaline; gradual smooth boundary. (0 to 15 inches thick)
Bk1--7 to 25 inches; pale brown (10YR 6/3) silty clay, brown (10YR 5/3) moist; with ped exteriors slightly darker than crushed color; strong fine subangular blocky structure; slightly hard, firm; few fine roots; few films and threads of calcium carbonate; calcareous; moderately alkaline; gradual smooth boundary. (10 to 30 inches thick)
Bk2--25 to 60 inches; very pale brown (10YR 7/3) silty clay, yellowish brown (10YR 5/4) moist; moderate fine subangular blocky structure; hard, firm; common medium and coarse soft masses and concretions of calcium carbonate; calcareous; moderately alkaline; gradual smooth boundary. (10 to 40 inches thick)
BCk--60 to 66 inches; very pale brown (10YR 7/3) silty clay, yellowish brown (10YR 5/4) moist; few fine faint grayish brown mottles; weak medium subangular blocky structure; very hard, firm; few medium and coarse calcium carbonate concretions; calcareous; moderately alkaline.
TYPE LOCATION: Collin County, Texas; in a cultivated field 100 feet east of county road, about 5.5 miles north-northwest of McKinney. (To reach location, go 5.2 miles west on Farm Road 543 from its intersection with Texas Highway 75 north of McKinney, then 0.7 mile west on a gravel road and 0.1 mile south on a county road.)
RANGE IN CHARACTERISTICS: Solum thickness ranges from 40 to more than 60 inches. The texture of the control section is silty clay, silty clay loam, or clay loam with total clay content ranging from 30 to 50 percent and silicate clay content ranging from 25 to 35 percent. Total carbonates in the control section range from 40 to 75 percent. Visible accumulations of secondary lime occur in the upper BK horizon with the highest concentration occurring at depths of about 25 inches. Coarse fragments, consisting of rounded limestone and chert pebbles range from none to about 5 percent by volume.
The A horizon has hue of 10YR or 2.5Y, with value of 5 or 6 and chroma of 2 to 4. In some pedons, A horizons less than 10 inches thick have moist values and chromas of 3.5 or less. Texture is silty clay, silty clay loam or clay loam.
The Bk and BCk horizons are in hues of 10YR, 2.5Y or 5Y, values of 5 through 7, and chromas of 2 through 6. Texture is silty clay, silty clay loam, clay loam or loam.
In some pedons, a 2C horizon occurs at depths of 40 to 75 inches and consists of loamy material with 35 to 75 percent rounded siliceous pebbles.
COMPETING SERIES: These include the Howe and McLennan series in the same family and the similar Brackett, Cuthand, Lamar, Seawillow and Whitewright series. Brackett and Whitewright soils have sola less than 20 inches thick. Cuthand soils have less than 18 percent clay in the control section. Howe soils have sola 20 to 40 inches thick over weakly cemented chalky limestone. Lamar soils have mixed mineralogy. McLennan soils contain flaggy fragments of limestone and have sola 20 to 40 inches thick. Seawillow soils have a loamy control section.
GEOGRAPHIC SETTING: Altoga soils are on gently sloping to strongly sloping erosional uplands, beveled edges of old high terraces, footslopes, and alluvial fans. Surfaces are generally convex and slopes range from 1 to 12 percent, dominantly 5 to 8 percent. The soil formed in calcareous clayey sediments several feet thick. The climate is moist subhumid to dry subhumid with the mean annual precipitation ranging from 28 to 40 inches. Mean annual temperature ranges from 64 degrees to 69 degrees F. Thornthwaite annual P-E index ranges from 42 to 64.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the Howe and Whitewright of the competing series, as well as the Branyon, Heiden, Lewisville and Stephen series. Branyon and Heiden soils are clayey and have intersecting slickensides. Lewisville and Stephen soils have mollic epipedons. In addition, Stephen soils are less than 20 inches thick.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderate permeability.
USE AND VEGETATION: Mainly pasture although sizeable areas are used for small grain. Most areas have been previously cultivated or used for limited crops. Originally, tall grass prairie with occasional brush motts in places, now mostly low quality grasses.
DISTRIBUTION AND EXTENT: Texas, possibly Oklahoma. Most areas are in the northern part of the Blackland Prairie and in the Grand Prairie along the major streams. Altoga soils are of moderate extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Travis County, Texas; 1969.
REMARKS: Classification was changed 11/89 from Typic Ustochrepts to Udic Ustochrepts.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The Ap horizon from 0 to 7 inches.
Cambic horizon - The Bk horizon from 7 to 66 inches.
Carbonates - Calcium carbonate equivalent ranges from 40 to 75 percent in the control section.