LOCATION MCLENNAN TXEstablished Series
TAXONOMIC CLASS: Fine-silty, carbonatic, thermic Udic Haplustepts
TYPICAL PEDON: McLennan clay loam--cropland. (Colors are for dry soil unless otherwise stated.)
A--0 to 7 inches; grayish brown (2.5Y 5/2) clay loam, dark grayish brown (2.5Y 4/2) moist; moderate fine subangular blocky structure; hard, friable; common very fine and fine roots; common wormcasts; common channers 2 to 6 inches across, few flaggy limestone fragments that are 1 inch thick and 6 to 10 inches across; calcium carbonate equivalent is 50 percent; violently effervescent; moderately alkaline; clear smooth boundary. (3 to 8 inches thick)
Bw--7 to 14 inches; light olive brown (2.5Y 5/4) clay loam, olive brown (2.5Y 4/4) moist; moderate medium prismatic structure parting to moderate subangular blocky; hard, firm; common very fine and fine roots; calcium carbonate equivalent is 70 percent; few medium calcium carbonate concretions; violently effervescent; moderately alkaline; clear smooth boundary. (0 to 18 inches thick)
Bk1--14 to 24 inches; light yellowish brown (2.5Y 6/4) clay loam, yellowish brown (10YR 5/4) moist; moderate medium prismatic structure parting to moderate very fine subangular blocky; hard, firm; few very fine and fine roots; calcium carbonate equivalent is 70 percent; few medium soft masses of calcium carbonate; common medium calcium carbonate concretions; violently effervescent; moderately alkaline; clear smooth boundary. (8 to 20 inches thick)
Bk2--24 to 32 inches; light yellowish brown (2.5Y 6/4) clay loam, yellowish brown (10YR 5/4) moist; moderate medium prismatic structure parting to moderate very fine subangular blocky; hard, firm; few very fine and fine roots; calcium carbonate equivalent is 70 percent; common medium soft masses of calcium carbonate; common medium calcium carbonate concretions; violently effervescent; moderately alkaline; clear smooth boundary. (0 to 20 inches thick)
Bk/C--32 to 80 inches; olive yellow (2.5Y 6/6) silty clay loam, light olive brown (2.5Y 5/6) moist; few strata of brownish yellow (10YR 6/6) loam up to 3 inches thick interbedded throughout; moderate medium subangular blocky structure; very hard, firm; few fine roots; about 5 to 10 percent medium distinct light brownish gray (2.5Y 6/2) shale fragments (C); calcium carbonate equivalent is 70 percent; common medium masses and concretions of calcium carbonate; few thin discontinuous quartzite limestone layers about 1 inch thick interbedded throughout; violently effervescent; moderately alkaline.
TYPE LOCATION: McLennan County, Texas; from the intersection of Texas Highway 317 and Farm Road 107 in Moody, 2.8 miles northwest on Texas Highway 317 to intersection with unpaved county road; 1.9 miles north on county road; 150 feet west of road in rangeland. Latitude: 31 degrees, 22 minutes, 12 seconds North; (Longitude: 97 degrees, 21 minutes, 35 seconds West.)
RANGE IN CHARACTERISTICS: Solum thickness ranges from 60 to 80 inches. The soil is calcareous and ranges from 40 to about 80 percent calcium carbonate equivalent. The texture of the soil is silty clay loam or clay loam throughout, with a silicate clay content ranging from 25 to 35 percent.
The A horizon has hue of 10YR or 2.5Y, value of 5 or 6, and chroma of 2 to 4. Fragments of channery and flaggy limestone range from a few to about 10 percent by volume. The fragments range from 2 to about 20 inches across the long axis and one half to 3 inches thick.
The B horizons have hue of 10YR or 2.5Y, value of 5 to 7, and chroma of 2 to 6. Some pedons have mottles of gray that are inherited from the parent material. Soft masses of calcium carbonate range from a few in the upper part (Bw) to about 25 percent by volume in the lower part (Bk). Calcium carbonate concretions range from none to about 10 percent by volume.
The Bk/C horizon has hue of 10YR to 5Y, value of 5 to 7, and chroma of 4. It contains strata of limestone 1 to 4 inches thick interbedded with shale, clay, claystone, siltstone, silty clay loam, clay loam or loam. Soft masses and concretions of calcium carbonate range from few to common.
COMPETING SERIES: These include the Altoga and Howe series in the same family, and the similar Austin, Brackett, Cranfill, Cuthand, Ellis, Kerrville, Lamar, Lott, Seawillow and Whitewright series. Altoga soils do not contain flaggy fragments of limestone or dense substrata and typically occur on old high terraces, footslopes and alluvial fans. Howe soils have a paralithic contact to chalk. Austin and Lott soils have mollic epipedons. Brackett, Cranfill, Lamar and Seawillow soils are in a fine-loamy family, in addition, Lamar soils have less than 40 percent calcium carbonate equivalent. Cuthand soils are in a coarse-silty family. Ellis soils are in a fine family, have vertic properties, and are noncalcareous. Kerrville soils contain more than 5 percent fragments in the control section. Whitewright soils are shallow over chalk.
GEOGRAPHIC SETTING: McLennan soils are on upland ridges and upper sideslopes. Slope gradients are mainly 8 to 15 percent but range from 3 to 20 percent. The soil formed in shale, clay or claystone interbedded with flaggy limestone, mainly of the Eagle Ford Group of upper Cretaceous Age. Mean annual precipitation ranges from about 30 to 40 inches. The mean annual temperature ranges from 64 to 68 degrees. Frost free period is 230 to 250 and elevation ranges from 600 to 800 feet. Thornthwaite annual P-E indices is from 50 to 64.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Austin and Lott series and the Ferris and Heiden series. The Austin and Lott soils have mollic epipedons and typically are on smoother less sloping landscapes. Ferris and Heiden soils are on similar positions, are in a fine family, and have intersecting slickensides.
DRAINAGE AND PERMEABILITY: Well drained; runoff is low on 3 to 5 percent slopes and medium on 5 to 20 percent slopes; moderately slow permeability.
USE AND VEGETATION: Used for pasture as well as cropland. The main grasses are common and improved bermudagrass and K.R. bluestem. Native vegetation includes little bluestem, silver bluestem, sideoats grama, Texas wintergrass and a few scattered elm and oak trees. Small grain and grain sorghum are the main crops grown.
DISTRIBUTION AND EXTENT: The Blackland Prairie of north-central Texas. The soil is not extensive.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: McLennan County, Texas; 1992.
REMARKS: McLennan soils have formerly been included with the Ferris or Sumter Series.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to a depth of 7 inches.
Cambic horizon - 7 to 14 inches.
Calcic horizon - the zone from 14 inches to 80 inches.