LOCATION STOVALL TX

Established Series
Rev. RAC/JLR/ACT
07/2012

STOVALL SERIES

The Stovall series consists of very deep, well drained, moderately permeable soils that formed in calcareous loamy valley fill alluvium predominantly from limestone hills and mountains materials. These nearly level to very gently sloping soils are on alluvial flats, broad upland plains and valleys. Slopes range from 0 to 3 percent.

TAXONOMIC CLASS: Fine-silty, mixed, superactive, thermic Ustic Haplocalcids

TYPICAL PEDON: Stovall silt loam - rangeland. (Colors are for dry soil unless otherwise specified.)

A1--0 to 4 inches; pale brown (10YR 6/3) silt loam, brown (10YR 5/3) moist; moderate medium granular structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; common very fine and fine pores; surface crust is 5 to 10 mm thick; few worm casts; violently effervescent; moderately alkaline; clear smooth boundary (2 to 10 inches thick).

A2--4 to 9 inches; brown (7.5YR 5/4) silt loam, brown (7.5YR 4/3) moist; moderate medium granular structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; common fine pores; violently effervescent; moderately alkaline; clear smooth boundary (4 to 8 inches thick).

Bk1--9 to 18 inches; light brown (7.5YR 6/4) silty clay loam, brown (7.5YR 5/4) moist; moderate medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; common fine pores; common fine films, threads, and masses of calcium carbonate; violently effervescent; moderately alkaline; clear smooth boundary.

Bk2--18 to 27 inches; light brown (7.5YR 6/4) silty clay loam, brown (7.5YR 5/4) moist; moderate medium subangular blocky structure; hard, friable, moderately sticky and moderately plastic; few very fine and fine roots; common fine pores; common fine films, threads, and masses of calcium carbonate; violently effervescent; moderately alkaline; gradual wavy boundary.

Bk3--27 to 36 inches; light brown (7.5YR 6/4) silty clay loam, brown (7.5YR 5/4) moist; weak medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; few very fine and fine roots; few fine pores; common fine films, threads, and masses of calcium carbonate; violently effervescent; moderately alkaline; gradual wavy boundary.

Bk4--36 to 60 inches; pink (7.5YR 7/4) silty clay loam, brown (7.5YR 5/4) moist; weak fine subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; few very fine and fine pores; many fine films, threads, and masses of calcium carbonate; violently effervescent; moderately alkaline; gradual wavy boundary. (Combined thickness of the calcic horizon is 50 to 80 inches.)

Bk5--60 to 80 inches; pink (7.5YR 7/4) silty clay, brown (7.5YR 5/4) moist; weak fine subangular blocky structure; hard, firm, very sticky and moderately plastic; common very fine and fine pores; many fine films, threads, and masses of calcium carbonate; violently effervescent; moderately alkaline.

TYPE LOCATION: Brewster County, Texas; from the junction of U.S. Highway 67 and U. S. Highway 90 approximately 8 miles east of Alpine; 4.6 miles north on U. S. Highway 67; 3.5 miles east on dirt road; 0.35 miles north on ranch trail along fence; 40 feet west in range. (Latitude: 30 degrees, 26 minutes, 18 seconds North; Longitude: 103 degrees, 26 minutes, 13 seconds West.)

RANGE IN CHARACTERISTICS:

Soil moisture: Ustic aridic moisture regime

Depth to calcic horizon: 6 to 15 inches

Silicate clay content: 22 to 35 percent

Limestone and caliche coarse fragments: 0 to 15 percent below 40 inches

Calcium carbonate content: averages 20 to 40 percent but ranges to 50 percent in some horizon within the pedon.

A horizon
Hue: 7.5YR, 10YR
Value: 4 to 6, dry or moist
Chroma: 2 to 4, dry or moist
Texture: silt loam, silty clay loam, clay loam
Total clay content: 22 to 35 percent
Silicate clay content: 15 to 30 percent
Some pedons have value and chroma less than 3.5, but the epipedon is not moist for 90 cumulative days or more in most years.

Bk horizons
Hue: 7.5YR, 10YR
Value: 4 to 8, dry or moist
Chroma: 2 to 6, dry or moist
Texture: silt loam, silty clay loam, clay loam, silty clay
Total clay content: 30 to 50 percent
Silicate clay content: 25 to 35 percent
Calcium carbonate: ranges from a few films and threads to many masses and concretions.

COMPETING SERIES: These are the Conchas (NM), Hoban (TX), Poquita (NM), Quay (NM), and Reagan (TX) series. Conchas soils have a lithic contact of sandstone between 20 and 40 inches. Hoban soils have gypsic horizons between 40 and 60 inches. Poquita soils have hue of 5YR or redder in the Bk horizons. Quay, Poquita, and Reagan soils have calcic horizons beginning between 15 and 40 inches. In addition, Conchas, Poquita, and Quay soils are in the Pecos- Canadian Plains and Valleys and are moist in May and June. Reagan soils are in the Edwards Plateau and are moist in May and June.

GEOGRAPHIC SETTING: Stovall soils are on broad nearly level to gently sloping plains, valleys, alluvial flats, and alluvial fans. Slopes are 0 to 3 percent. The soil formed in medium to moderately fine textured alluvial materials that are high in calcium carbonate. Mean annual precipitation ranges from 12 to 16 inches, and mean annual air temperature ranges from 60 to 65 degrees F. Frost-free period ranges from 200 to 260 days, and elevation ranges from 3,200 to 4,500 feet.

GEOGRAPHICALLY ASSOCIATED SOILS: These include the Bissett, Cienega, Crossen, and Sutherland soils. Bissett soils are shallow to limestone bedrock and are on limestone hills and mountains. Cienega, and Southerland soils have more than 35 percent coarse fragments in the texture control section and are on fans and ridges above the alluvial plains. In addition, the Crossen and Southerland soils are less than 20 inches to indurated caliche.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate. Runoff is negligible on slopes less than 1 percent, and very low on 1 to 3 percent slopes.

USE AND VEGETATION: This soil is used for livestock grazing. Native vegetation is mainly drought tolerant short and mid grasses such as tobosa, blue grama, black grama, sideoats grama, bush muhly, and burrograss.

DISTRIBUTION AND EXTENT: Far west Texas in MLRA 42. The series is extensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona

SERIES ESTABLISHED: Brewster County, Texas, 1997.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon The zone from 0 to 9 inches (A horizons)

Calcic horizon The zone 9 to 80 inches (Bk horizons)

These soils were previously included in the Reagan and Hodgins series.

Update and revision for recorrelation of Brewster County, TX, Main Part, 2/12/08, CEM

Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Eleventh Edition, 2010

Revised for the correlation of Hudspeth County, Texas (Main Part) and Culberson County, Texas (Main Part); July, 2012, NMS

ADDITIONAL DATA: Classification was changed from carbonatic mineralogy to mixed mineralogy in 1992 based on NSSL data (S92TX-043-005), and from additional local laboratory data.

National Cooperative Soil Survey
U.S.A.