LOCATION CHOKE TX

Established Series
PDH-GWH-CKH
11/2010

CHOKE SERIES

The Choke series consists of very deep, well drained, moderately permeable soils. These soils formed in calcareous loamy residuum over tuffaceous sediments. These gently sloping soils are on erosional remnants. Slopes range from 1 to 5 percent.

TAXONOMIC CLASS: Fine-silty, mixed, superactive, hyperthermic Aridic Calciustolls

TYPICAL PEDON: Choke silty clay loam, in rangeland; elevation is 60 meters (200 feet). (Colors are for dry soil unless otherwise noted.)

A1--0 to 10 cm (0 to 4 in); dark grayish brown (10YR 4/2) silty clay loam; very dark grayish brown (10YR 3/2) moist; moderate fine granular structure; slightly hard, friable; common very fine and fine, and few medium and coarse roots; few very fine and fine tubular pores; common termite casts; slightly effervescent; moderately alkaline; clear smooth boundary.

A2--10 to 25 cm (4 to 10 in); very dark grayish brown (10YR 3/2) silty clay loam; very dark brown (10YR 2/2) moist; moderate fine granular structure; slightly hard, friable; common very fine and fine, and few medium and coarse roots; common very fine and fine tubular pores; common termite casts; slightly effervescent; moderately alkaline; clear smooth boundary. (Combined thickness is 18 to 48 cm [7 to 19 in].)

Bw1--25 to 41 cm (10 to 16 in); dark grayish brown (10YR 4/2) silty clay loam; very dark grayish brown (10YR 3/2) moist; weak medium prismatic structure parting to moderate fine subangular blocky; slightly hard, friable; common very fine and fine, and few medium and coarse roots; common very fine and fine tubular pores; common termite casts; strongly effervescent; moderately alkaline; clear smooth boundary.

Bw2--41 to 61 cm (16 to 24 in); grayish brown (10YR 5/2) silty clay loam; dark grayish brown (10YR 4/2) moist; weak fine and medium prismatic structure parting to moderate fine subangular blocky; hard, friable; common very fine and fine, and few medium roots; common very fine and fine and few medium tubular pores; few threads of calcium carbonate; common termite casts; violently effervescent; moderately alkaline; gradual smooth boundary. (Combined thickness is 0 to 46 cm [0 to 18 in].)

Bk1--61 to 86 cm (24 to 34 in); light brownish gray (10YR 6/2) silty clay loam; grayish brown (10YR 5/2) moist; weak fine and medium prismatic structure parting to moderate fine and medium subangular blocky; hard, friable; common very fine and fine, and few medium and coarse roots; many very fine and fine, and common medium tubular pores; 5 percent films and threads of calcium carbonate; common termite casts; violently effervescent; moderately alkaline; gradual smooth boundary.

Bk2--86 to 122 cm (34 to 48 in); light gray (10YR 7/2) silt loam; very pale brown (10YR 7/3) moist; weak fine and medium prismatic structure parting to moderate fine and medium subangular blocky; hard, friable; common very fine and fine, and few medium and coarse roots; many very fine and fine, and common medium tubular pores; 5 percent films and threads of calcium carbonate; few termite casts; violently effervescent; moderately alkaline; gradual smooth boundary.

Bk3--122 to 147 cm (48 to 58 in); light gray (10YR 7/2) loam; very pale brown (10YR 7/3) moist; weak fine and medium prismatic structure parting to moderate fine and medium subangular blocky; slightly hard, very friable; few very fine and fine roots; common very fine and fine tubular pores; 3 percent films and threads of calcium carbonate; few termite casts; violently effervescent; moderately alkaline; clear smooth boundary. (Combined thickness is 25 to 102 cm [10 to 40 in].)

BCk--147 to 185 cm (58 to 73 in); light gray (10YR 7/2) loam; very pale brown (10YR 7/3) moist; weak fine subangular blocky structure; soft, very friable; few very fine and fine roots; common very fine and fine tubular pores; few rounded siliceous pebbles mostly along lower boundary; 2 percent fine threads and concretions of calcium carbonate; strongly effervescent; moderately alkaline; abrupt wavy boundary. (Thickness is 0 to 43 cm [0 to 17 in].)

2Cd--185 to 213 cm (73 to 84 in); very pale brown (10YR 7/3) weakly cemented tuffaceous siltstone; pale brown (10YR 6/3) moist; massive; extremely hard, extremely firm; few very fine, fine, medium, and coarse roots along fractures; fractures are spaced 3 to 8 inches apart; common very fine and fine tubular pores; few coatings of calcium carbonate along vertical and horizontal fractures; strongly effervescent; moderately alkaline.

TYPE LOCATION: Live Oak County, Texas; from the intersection of U.S. Highway 59 and U.S. Highway 281 in George West, 15.8 miles north on U.S. Highway 281, 3.9 miles north on Interstate Highway 37, 1.0 mile east on Farm Road 2049, 1.6 miles north on county road, 0.45 mile west in rangeland. Comanche Hills, USGS topographic quadrangle; Latitude: 28 degrees, 36 minutes, 24 seconds N; Longitude: 98 degrees, 11 minutes, 24 seconds W.; NAD83.

RANGE IN CHARACTERISTICS:

Soil Moisture: An aridic ustic moisture regime. The soil moisture control section is moist in some or all parts for less than 90 consecutive days in normal years. June to August and December to February are the driest months, while September to November and March to May are the wettest months.
Solum thickness: 150 to 200 cm (60 to 80 in)
Depth to densic contact: 150 to 200 cm (60 to 80 in)
Particle-size control section (weighted average)
Clay content: (non-carbonate) 20 to 35 percent
Sand content: (coarser than very fine sand) 4 to 15 percent

Electrical conductivity ranges from 0.4 to 2 dS/m in the A, Bw, and upper part of the Bk horizons and 4 to 12 dS/m in the lower part of the Bk and 2Cr horizon.

A Horizon
Hue: 10YR
Value: 3 to 5
Chroma: 2 or 3
Texture: silt loam or silty clay loam
Calcium carbonate equivalent: 5 to 15 percent
Effervescence: slight to violent
Electrical conductivity: 0.4 to 2 dS/m

Bw Horizons
Hue: 10YR
Value: 4 to 6
Chroma: 2 to 4
Texture: loam, silt loam, silty clay loam or clay loam
Calcium carbonate equivalent: 10 to 15 percent
Effervescence: slight to violent
Electrical conductivity: 0.4 to 2 dS/m

Bk Horizons
Hue: 10YR
Value: 5 to 7
Chroma: 2 to 4
Texture: loam, silt loam, silty clay loam or clay loam
Calcium carbonate equivalent: 15 to 30 percent
Effervescence: slight to violent
Electrical conductivity: 0.4 to 2 dS/m in the upper part and 4 to 12 dS/m in the lower part

BCk Horizon
Hue of 10YR or 2.5Y
Value of 6 to 8
Chroma of 2 to 4
Texture is silt loam, loam or silty clay loam
Calcium carbonate equivalent ranges from 10 to 30 percent
Effervescence: slight to violent
Electrical conductivity: 4 to 12 dS/m

2Cd Horizon
Hue: 10YR to 5Y
Value: 7 or 8
Chroma: 2 to 4
Cementation: weakly cemented siltstone that slakes in water within 1 hour
Excavation difficulty: low to moderate
Calcium carbonate equivalent: 10 to 20 percent
Reaction: slightly alkaline or moderately alkaline

COMPETING SERIES: These are the Elindio(TX) and Uvalde (TX) series in the same family. Similar soils are the Castroville(TX), Hidalgo(TX), Houla(TX), and Sarnosa(TX) series.
Castroville soils: formed in alluvium derived from limestone; on a terrace or alluvial fan landform; have sola more than 200 cm (80 in) thick
Elindio soils: formed in alluvium derived from limestone; on terrace or alluvial fan positions; sola more than 200 cm (80 in) thick; are dry in the moisture control section for slightly longer periods
Uvalde soils: formed in alluvium derived from limestone; on terrace or alluvial fan positions and have sola more than 200 cm (80 in) thick
Hidalgo soils: have a fine-loamy control section
Houla soils: have a fine-loamy control section; sola 100 to 150 cm (40 to 60 in) thick
Sarnosa soils: have a coarse-loamy control section

GEOGRAPHIC SETTING:
Parent material: loamy materials over weakly cemented siltstone of the tuffaceous Catahoula Formation
Landscape: inland, dissected coastal plain
Landform: gently sloping erosion remnants
Slope: 1 to 5 percent
Mean annual precipitation range: 559 to 711 mm (22 to 28 in)
Mean annual temperature range: 21 to 23 degrees C (70 to 74 degrees F)
Frost-free period: 285 to 300 days
Elevation: 50 to 122 m (165 to 400 ft)
Thornthwaite annual P-E indices: 27 to 40

GEOGRAPHICALLY ASSOCIATED SOILS: These include the Condido (TX), Eloso (TX), Pavelek (TX), and Rosenbrock (TX) soils.
Eloso soils: are on slightly lower positions and are clayey throughout
Rosenbrock soils: are on slightly lower positions and are clayey throughout
Condido and Pavelek soils: are on similar positions and have a petrocalcic horizon within 51 cm (20 in) of the surface

DRAINAGE AND PERMEABILITY: well drained. moderate permeability. Runoff is very low on slopes of 1 to 3 percent and low on slopes of 3 to 5 percent.

USE AND VEGETATION: Used mainly for rangeland and wildlife habitat. Native grasses are plains bristlegrass, hooded windmillgrass, pink pappusgrass, Arizona cottontop, and twoflower and fourflower trichloris. Woody plants include guajillo, mountain laurel, paloverde, desert yaupon, mesquite, and agarita. (Gray Sandy Loam range site, PZ 18-25, R083BY421TX).

DISTRIBUTION AND EXTENT: Northern, Western and Central Rio Grande Plain, Texas; LRR I; MLRA 83A, 83C; minor extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas

SERIES ESTABLISHED: Live Oak County, Texas; 1997. The name is named for Choke Canyon Reservoir.

REMARKS: Diagnostic horizons and features recognized in this pedon:

Mollic epipedon: 0 to 41 cm (0 to 16 in) (A and Bw1 horizons)

Cambic horizon: 41 to 61 cm (16 to 24 in) (Bw horizons)

Calcic horizon: 61 to 122 cm (24 to 48 in) (Bk horizons)

Densic contact: 185 cm (73 in) (top of 2Cd horizon)

ADDITIONAL DATA: NSSL data from Live Oak County (S91TX-297-005)

TAXONOMIC VERSION: Keys to Soil Taxonomy, Eleventh Edition, 2010

National Cooperative Soil Survey
U.S.A.