LOCATION PEDERNALES TXEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Typic Paleustalfs
TYPICAL PEDON: Pedernales fine sandy loam--cultivated. (Colors are for dry soil unless otherwise stated).
Ap--0 to 11 inches; reddish brown (5YR 4/4) fine sandy loam, dark reddish brown (5YR 3/4) moist; weak fine subangular blocky and granular structure; hard, friable; few fine roots; neutral; clear smooth boundary. (6 to 15 inches thick)
Bt1--11 to 20 inches; red (2.5YR 5/6) sandy clay, red (2.5YR 4/6) moist; moderate medium prismatic and moderate medium blocky structure; very hard, very firm, sticky and very plastic; few fine tubular pores; few insect casts and burrows; common clay films; slightly alkaline; gradual smooth boundary. (8 to 20 inches thick)
Bt2--20 to 37 inches; red (2.5YR 5/6) sandy clay, red (2.5YR 4/6) moist; weak medium blocky structure; very hard, very firm, sticky and very plastic; few fine tubular pores; common clay films; slightly alkaline; gradual smooth boundary. (10 to 20 inches thick)
Btk--37 to 43 inches; yellowish red (5YR 5/6) sandy clay loam, yellowish red (5YR 4/6) moist; weak coarse blocky structure; hard, firm, sticky; few patchy clay films; 10 to 15 percent masses of calcium carbonate; slightly effervescent; moderately alkaline; clear smooth boundary. (6 to 20 inches thick)
BCtk--43 to 80 inches; light reddish brown (5YR 6/4) sandy clay loam, reddish brown (5YR 5/4) moist; weak coarse blocky structure; hard, firm, sticky and plastic; few patchy clay films; 25 percent masses of calcium carbonate; few weakly cemented limestone fragments; violently effervescent; moderately alkaline.
TYPE LOCATION: Gillespie County, Texas; 2.5 miles southwest of County Courthouse in Fredericksburg; 50 feet southeast of State Highway 16 and 125 feet southwest of intersection of Highway 16 and FR 2093.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 60 to more than 80 inches. Secondary carbonates are at depths of 28 to 50 inches. Some pedons contain small amounts of limestone and siliceous pebbles, usually less than 5 percent.
The A horizon has hue of 5YR to 10YR, value of 4 to 6, and chroma of 3 to 6. Texture is loamy fine sand or fine sandy loam. Reaction is slightly acid to sightly alkaline.
Some pedons have E horizons that are 1 to 2 units of value higher than the A1 horizon.
The Bt horizon has hue of 2.5YR to 7.5YR, value of 4 to 6, and chroma of 4 to 8. Also some pedons are red (10R 5/6). Yellowish and brownish masses of iron accumulation are in the lower part of the Bt horizon in some pedons. Texture is clay loam, sandy clay, or clay. The clay content of the Bt horizons ranges from 35 to 55 percent and decreases with depth. The Bt horizon is slightly acid to slightly alkaline and some pedons are moderately alkaline in the lower part.
The BCtk horizon has hue of 2.5YR to 10YR, value of 5 to 8, and chroma of 2 to 6. Texture is sandy clay loam, clay loam, or sandy clay. Some pedons contain thin strata of soft limestone within this horizon. It contains from 5 to 30 percent by volume calcium carbonate in the form of concretions and masses.
Some pedons have C horizons between 60 and 80 inches. This horizon is composed of massive or weakly cemented sandstone.
COMPETING SERIES: These are the Castell, Hamby, Shatruce, Voca, Weswind, Wichita and Winters series. Similar soils are the Truce, Minwells, and Windthorst series. Castell soils are 20 to 40 inches to a lithic contact with gneiss bedrock. Hamby soils do not have secondary carbonates above 50 inches. Shatruce soils have sola 20 to 40 inches to shale that has clay texture. Truce soils have sola 40 to 60 inches thick and do not have calcic horizons. Voca soils have sola 36 to 60 inches thick to a contact with fractured granite bedrock. Weswind soils have sola less than 60 inches thick and are moderately well drained. Wichita soils contain secondary carbonates within 30 inches of the surface. Winters soils have calcic horizons at depth of more than 45 inches. Minwells soils have gravelly substrata below 40 inches. Windthorst soils do not have calcic horizons.
GEOGRAPHIC SETTING: Pedernales soils are in broad, nearly level to moderately sloping valleys flanked by receding limestone scarps. Slopes are mainly about 2 percent but range from 0 to 8 percent. The soil formed in highly calcareous sandy loam, sandy clay loam, clay sediments of Lower Cretaceous age. Mean annual precipitation ranges from 24 to 32 inches, and mean annual temperature ranges from 65 to 68 degrees F. Frost free days range from 220 to 240 days, and elevation ranges from 700 to 1,700 feet. Annual Thornthwaite P-E indices ranges from 36 to 46.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Brackett, Hext, and Menard series. Brackett and Hext soils contain high levels of calcium carbonate, and do not have argillic horizons. These soils are at higher elevations on adjoining areas over limestone or calcareous sandstone. Menard soils have less than 35 percent clay content in the upper Bt horizon, and are on similar surfaces.
DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderately slow. Runoff is negligible on slopes less than 1 percent, very low on 1 to 3 percent slopes, low on 3 to 5 percent slopes, and medium on 5 to 8 percent slopes.
USE AND VEGETATION: Used mainly for growing grain sorghums, small grain, and peaches. Native vegetation is post oak, mid and tall grasses.
DISTRIBUTION AND EXTENT: Mainly in the Grand Prairie, Texas North Central Prairie, Central Basin and Eastern part of the Edwards Plateau of Texas. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Reconnaissance Soil Survey of South Central Texas; 1913.
REMARKS: The soil is in the superactive cation exchange activity class based on TAMU laboratory data from Gillespie County, Texas. Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - 0 to 11 inches. (Ap horizon)
Pale feature - abrupt textural change at 11 inches.
Argillic horizon - 11 to 80 inches. (Bt, Btk, and BCtk horizons)
Calcic horizon - 37 to 80 inches. (Btk and BCtk horizons)
ADDITIONAL DATA: TAMU Soil Characterization Laboratory data from Gillespie County, TX, S81TX-171-1; NSSL data from Menard County, TX, S62TX-164-1-1 & S62TX-164-4-1.
Soil Interpretation Record No.: TX0139