LOCATION STEPHEN TXEstablished Series
TAXONOMIC CLASS: Clayey, mixed, active, thermic, shallow Udorthentic Haplustolls
TYPICAL PEDON: Stephen silty clay--cropland. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 8 inches; dark brown (7.5YR 4/2) silty clay, dark brown (7.5YR 3/2) moist; moderate fine subangular blocky and granular structure parting to very fine subangular blocky structure; hard, firm, sticky, plastic; many fine roots; few fine chalk fragments; calcareous, moderately alkaline; abrupt wavy boundary. (7 to 20 inches thick)
C/A--8 to 12 inches; about 65 percent platy chalk fragments and platy chalk in place and about 35 percent dark brown (7.5YR 3/3) moist silty clay in the horizontal and vertical crevices and between the loose chalk fragments; few to strongly cemented cobblestones and limestone; few fine roots; few fine pores; calcareous, moderately alkaline; abrupt irregular boundary. (0 to 6 inches thick)
Cr--12 to 28 inches; pink (5YR 8/3) and white (10YR 8/2) platy chalk this is less hard than 3, Mohs scale; few thin tongues of dark brown calcareous silty clay in crevices between some chalk plates.
TYPE LOCATION: McLennan County, Texas; from the intersection of Farm Road 1695 and Farm Road 2837 in Lorena, 0.6 mile northwest on Farm Road 2837 to intersection with county road, 300 feet west and 100 feet north of intersection in cropland.
RANGE IN CHARACTERISTICS: Solum thickness to chalky limestone ranges from 7 to 20 inches. The chalky limestone, when moist, can be cut with a spade. The layer below the A horizon ranges from 40 to 80 percent or more calcium carbonate equivalent.
The A horizon has hue of 7.5YR or 10YR; value of 3 to 5, and chroma of 1 to 3. It is clay, silty clay, silty clay loam, or clay loam with 35 to 55 percent clay. Chalk fragments in the A horizon range from 2 to 15 percent by volume. Olive mottles or streaks range from none to common in the lower part to the A horizon. The lower boundary of the A horizon ranges from wavy to irregular.
The C/A or A/C horizons, where present, have color and texture similar to those of the A and Cr horizons.
The Cr horizon is interbedded chalk and limy earths or soft limestone and limy earths. It has hue of 5YR to 10YR in shades of pink, white, and gray.
COMPETING SERIES: There are no series in the same family. Similar soils are Brackett, Castephen, Doss, Eckrant, Purves, Real, and Whitewright series. Brackett and Whitewright soils lack a mollic epipedon. Brackett, Castephen, Doss, Real, and Whitewright soils have carbonatic mineralogy and contain less than 35 percent silicate clay. Eckrant and Purves soils have a Lithic contact with indurated limestone. In addition, Eckrant and Real soils contain more than 35 percent coarse fragments.
GEOGRAPHIC SETTING: Stephen soils are on uplands. Surfaces are plane to convex, with gradients mainly less than 5 percent, but range from 1 to 8 percent. The soils formed in interbedded chalk, marl, or soft limestone rubble, mainly of the Austin Formation. The climate is warm and subhumid; mean annual precipitation ranges from 30 to 42 inches, mean annual temperature from 63 to 69 degrees F., and the Thornthwaite annual P-E indices from 44 to 66.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Altoga, Austin, Brackett, Eddy, and Lott series. All of these soils have carbonatic
mineralogy and less than 35 percent clay in the control section. In addition; Altoga, Brackett, and Eddy do not have mollic epipedons.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; medium internal drainage; moderately slow permeability.
USE AND VEGETATION: Mainly in cultivation and used for growing small grains. A few areas are in native range. Native grasses are little bluestem, sideoats grama, hairy grama, and buffalograss.
DISTRIBUTION AND EXTENT: The Blackland Prairie of Texas. The series is extensive.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Ellis County, Texas; 1962.
REMARKS: Classification was changed 11/89 from clayey, mixed, thermic, shallow Entic Haplustolls to clayey, mixed, thermic, shallow Udorthentic Haplustolls.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 8 inches, the Ap horizon.
Paralithic contact of chalk at a depth of 12 inches.