LOCATION ANGELO TXEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, thermic Aridic Calciustolls
TYPICAL PEDON: Angelo clay loam--cultivated. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 6 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; weak very fine granular and subangular blocky structure; hard, firm, sticky and plastic; common fine roots; violently effervescent; moderately alkaline; clear smooth boundary. (4 to 16 inches thick)
A--6 to 12 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; moderate very fine granular and moderate very fine and fine subangular blocky structure; hard, firm, sticky and plastic; few fine roots; violently effervescent; moderately alkaline; gradual wavy boundary. (1 to 10 inches thick)
Bw--12 to 28 inches; reddish brown (5YR 5/3) clay, reddish brown (5YR 4/3) moist; moderate very fine and fine subangular blocky and weak fine angular blocky structure; very hard, firm, very sticky and plastic; few roots and pores; shiny peds when moist; few wormcasts, violently effervescent; moderately alkaline; gradual smooth boundary. (8 to 30 inches thick)
Bk1--28 to 58 inches; pink (7.5YR 7/4) silty clay loam, reddish yellow (5YR 6/6) moist; moderate very fine and fine subangular blocky structure; hard, firm; few fine roots; contains 25 percent visible calcium carbonate mostly in soft masses; shiny peds when moist; violently effervescent; moderately alkaline; diffuse smooth boundary. (6 to 35 inches thick)
Bk2--58 to 92 inches; reddish yellow (5YR 6/6) silty clay loam, yellowish red (5YR 5/6) moist; weak very fine to fine subangular blocky structure; hard, firm; less than 5 percent visible calcium carbonate; shiny peds when moist; violently effervescent; moderately alkaline.
TYPE LOCATION: Tom Green County, Texas; 14.9 miles northeast of the Tom Green County Courthouse in San Angelo along U.S. Highway 67 to its intersection with a county road; 0.25 mile north along the county road from the intersection and 150 feet west of the county road.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 60 to more than 80 inches. Distinct calcium carbonate accumulations begin at depths ranging from 24 to 40 inches. COLE above the calcic horizon ranges from 0.07 to 0.10. COLE in the calcic horizon and to a depth of 1.25 meters ranges from 0.02 to 0.07. The silicate clay content of the 10- to 40- inch particle size control section ranges from 28 to 35 percent, with total clay ranging from 35 to 50 percent. The silicate clay fraction is dominated by smectite.
The A horizon has hue of 7.5YR or 10YR, value of 3 to 5, and chroma of 2 or 3. Texture is clay loam, silty clay loam, clay, or silty clay. Silicate clay ranges from 28 to 42 percent and total clay from 30 to 45 percent.
The Bw horizon has hue of 5YR to 10YR, value of 4 to 6, and chroma of 2 to 4. Texture is clay loam, silty clay loam, clay, or silty clay. In some pedons this horizon may contain a small amount of visible secondary carbonates.
The Bk horizons have hue of 5YR to 10YR, value of 5 through 8, and chroma of 2 through 6. The calcium carbonate equivalent of the Bk horizon ranges from 15 to 60 percent. Some pedons have two distinct horizons of calcium carbonate accumulation. Visible carbonate content ranges from 5 to 20 percent. Structure ranges from weak to moderate subangular blocky. Thickness of the calcic horizon is dominantly 6 to 40 inches but ranges to 60 inches in some pedons. Some pedons are underlain by limestone below 40 inches in depth.
COMPETING SERIES: There are no other series in this family. Similar series are Cuevoland, Elindio, Engle, Lewisville, Nuvalde, Quanah, Uvalde, and Venus. Cuevoland soils have mean annual air temperature of less than 59 degrees F. Elindio and Uvalde soils have mean annual soil temperatures of more than 72 degrees F. Engle and Venus soils are moist in the moisture control section for longer periods of time and have a fine-loamy control section. Lewisville, Nuvalde, and Quanah soils are moist in the moisture control section for longer periods of time and have COLE of less than 0.07.
GEOGRAPHIC SETTING: Angelo soils are on uplands, mainly ancient stream terraces. Slope gradients are dominantly less than 1 percent, but range up to 3 percent. The soil formed in calcareous loamy and clayey sediments. Mean annual precipitation ranges from 15 to 22 inches and mean annual temperature ranges from 64 to 70 degrees F. Frost-free days range from 210 to 240 and elevation ranges from 1,500 to 2,750 feet. Thornthwaite P-E indices range from 23 to 33.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Ector, Lipan, Mereta, Rioconcho and Veal series. The shallow Ector soils occur on limestone hills adjacent to Angelo soils. Lipan soils are grayer and occur in depressions. Mereta and Veal soils occupy higher positions in the landscape. Mereta soils have petrocalcic horizons and Veal soils are less clayey and have a much higher carbonate content. Rioconcho soils occur in narrow stream channels in lower positions that are subject to flooding.
DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderately slow. Runoff is negligible on 0 to 1 percent slopes and low on 1 to 3 percent slopes.
USE AND VEGETATION: These soils are mainly planted to grain sorghum, cotton, wheat, and forage crops. Many areas are in rangeland. Present native grasses are sideoats grama, cane bluestem, buffalograss, curlymesquite, Texas wintergrass, and threeawns. Mesquite trees are abundant.
DISTRIBUTION AND EXTENT: The Rolling Plains and Edwards Plateau of west central Texas. The series is extensive.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Tom Green County, Texas; 1971.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 12 inches. (Ap and A horizons)
Cambic horizon - 12 to 28 inches. (Bw horizons)
Calcic horizon - 28 to 58 inches. (Bk1 horizon)
Shrink-swell features - high shrink-swell behavior above the calcic horizon.
ADDITIONAL DATA: Lab data available from NSSL is one pedon 3/82 from the type location in Tom Green County, Texas, Nos. 814669-814673, and one pedon 3/82 Irion County, Texas Nos. 814663-814668. Also, one pedon 9/65 from Tom Green County, Texas, by Texas Tech No. S65TX-226-1, which is now considered to be outside the range of characteristic for the Angelo series as reclassified 10/82. As a result of the 1982 NSSL data, the classification of the Angelo series is changed from fine, mixed, thermic Torrertic Calciustolls, to fine-silty, mixed, thermic Aridic Calciustolls for the correlation of the Irion County, Texas, soil survey. The NSSL data shows the silicate clay fraction to be dominated by smectite, causing the A and B horizons above the calcic horizon to have high shrink swell properties with COLE of more than 0.07.