LOCATION LEWISVILLE TXEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, active, thermic Udic Calciustolls
TYPICAL PEDON: Lewisville silty clay--pasture. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 6 inches; dark grayish brown (10YR 4/2) silty clay; very dark grayish brown (10YR 3/2) moist; moderate very fine subangular blocky and granular structure; hard, friable; contains a few strongly cemented calcium carbonate concretions; calcareous; moderately alkaline; abrupt smooth boundary. (0 to 7 inches thick)
A--6 to 16 inches; dark grayish brown (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; hard, firm; few root channels; common strongly cemented calcium carbonate concretions about 2 to 5 mm in diameter; calcareous; moderately alkaline; gradual smooth boundary. (7 to 15 inches thick)
Bk1--16 to 34 inches; grayish brown (10YR 5/2) silty clay, dark grayish brown (10YR 4/2) moist; moderate fine subangular blocky structure; very hard, firm; common strongly cemented calcium carbonate concretions 2 to 5 mm in diameter; a few threads of soft calcium carbonate; calcareous; moderately alkaline; gradual smooth boundary. (13 to 30 inches thick)
Bk2--34 to 62 inches; pale brown (10YR 6/3) silty clay; brown (10YR 5/3) moist; weak subangular blocky structure; hard, firm; common soft masses of segregated calcium carbonate, few small, strongly cemented calcium carbonate concretions; calcareous; moderately alkaline.
TYPE LOCATION: Collin County, Texas; from the intersection of Farm Road 546 and Texas Highway 75 in McKinney, 5 miles southeast on Farm Road 546, 1.2 miles south on county road, 60 feet east in pasture.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 60 to about 80 inches. It is clay loam, silty clay loam, or silty clay with silicate clay content ranging from 24 to 35 percent. Calcium carbonate equivalent in the 10- to 40-inch control section ranges from about 20 to 40 percent.
The A horizon has color in hue of 7.5YR and 10YR, value of 3 to 5, and chroma of 2 and 3. Thickness is 10 to 20 inches.
The Bk1 horizon is grayish, brownish, or yellowish in hue of 2.5Y to 7.5YR, value of 4 to 6, and chroma of 2 to 4. Some pedons in hue of 10YR and 7.5YR have chroma of 6. Soft bodies, concretions, films, and threads of calcium carbonate comprise about 3 to 8 percent by volume.
The Bk2 horizon has colors similar to the Bk1 horizon except they have values about 1 or 2 units higher. Some pedons have hue of 5YR and chroma of 6. Secondary forms of calcium carbonate comprise 5 to about 15 percent by volume.
Some pedons are underlain at depths of 3 to 15 feet by sediments containing 15 to 50 percent gravel.
COMPETING SERIES: There are no other series in this family. Similar series are the Altoga, Austin, Nuvalde, Quanah, Venus, and Volente series. Nuvalde and Quanah soils are dry in the moisture control section for longer periods. Altoga and Austin soils have more than 40 percent calcium carbonate equivalent in the control section. In addition, Altoga soils lack mollic epipedons. Venus soils have fine-loamy control sections. Volente soils have more than 35 percent silicate clay content in the control section.
GEOGRAPHIC SETTING: Nearly level to rolling landscapes having plane to convex surfaces. Slopes range from 0 to 10 percent, but they are mostly 2 to 6 percent. The soil formed in ancient loamy and limy alluvium assumed to have originated in areas underlain by limestone. The climate is moist subhumid with an annual mean precipitation of about 28 to 38 inches and the Thornthwaite P-E index of 44 to 66. At the type location the mean annual temperature is 66 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Altoga, Venus, and Volente series and Eddy, Krum, and Stephen series. Altoga, Eddy, and Stephen soils occur on erosional surfaces at higher elevations. Eddy and Stephen soils are less than 20 inches thick and are underlain by chalk or weakly cemented limestone. In addition, Eddy soils contain more than 35 percent by volume of coarse fragments. Krum, Venus, and Volente soils occur at lower elevations as stream terraces or lower portions of narrow valleys. In addition, Krum soils have clayey control sections and vertic features of cracking widely and deeply when dry.
DRAINAGE AND PERMEABILITY: Well drained; runoff is slow to medium; permeability is moderate.
USE AND VEGETATION: Mostly cultivated, mainly to small grains. Originally vegetation was mid and tall grasses and a few widely separated elm, hackberry, and mesquite trees.
DISTRIBUTION AND EXTENT: Mainly in Texas, along major streams in the Blackland Prairies and the Grand Prairie; possibly in Oklahoma. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Denton County, Texas; 1918.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 16 inches, the Ap and A horizons.
Calcic horizon - 16 to 62 inches, the Bk horizons.