LOCATION COQUAT TX
Established Series
Rev. DA-WJG-ACT-GWH
11/2010
COQUAT SERIES
The Coquat series consists of very deep, somewhat poorly drained, very slowly permeable clays formed in clayey alluvium. These nearly level soils are on flood plains. Slopes range from 0 to 1 percent.
TAXONOMIC CLASS: Fine, smectitic, hyperthermic Sodic Haplusterts
TYPICAL PEDON: Coquat clay, 0.5 percent slope in rangeland; elevation is 92 meters (301 feet). (Colors are for dry soil unless otherwise stated.)
A--0 to 13 cm (0 to 5 in); grayish brown (10YR 5/2) clay, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure parting to weak fine angular blocky; very hard, very firm, very sticky, very plastic; common very fine and fine roots; few snail shell fragments; nonsaline; strongly effervescent; moderately alkaline; gradual wavy boundary. (Thickness is 8 to 25 cm [3 to 10 in].)
Bknss--13 to 91 cm (5 to 36 in); light brownish gray (10YR 6/2) clay, grayish brown (10YR 5/2) moist; common fine faint vertical streaks of grayish brown (10YR 5/2) clay; weak medium subangular blocky structure parting to moderate fine angular blocky; extremely hard; very firm; very sticky, very plastic; common fine and very fine roots; few fine rounded strongly cemented calcium carbonate nodules; few slickensides in lower part, nonsaline; exchangeable sodium percentage is 20; strongly effervescent; moderately alkaline; diffuse wavy boundary. (Thickness is 38 to 89 cm [15 to 35 in].)
Bknssz1--91 to 132 cm (36 to 52 in); pale brown (10YR 6/3) clay, brown (10YR 5/3) moist; weak medium subangular blocky structure parting to moderate fine angular blocky; extremely hard, very firm, very sticky, very plastic; common very fine and fine roots; few dark streaks; few slickensides; few fine rounded strongly cemented calcium carbonate nodules; few fine rounded weakly cemented black ferromangenese nodules; strongly saline; exchangeable sodium percentage is 30; strongly effervescent; moderately alkaline; diffuse wavy boundary. (Thickness is 38 to 64 cm [15 to 25 in].)
Bknssz2--132 to 165 cm (52 to 65 in); pale brown (10YR 6/3) clay, brown (10YR 5/3) moist; weak medium subangular blocky structure parting to moderate fine angular blocky; extremely hard, very firm, very sticky, very plastic; few very fine and fine roots; few dark streaks; few slickensides; few fine and medium distinct yellowish brown (10YR 5/6) and strong brown (7.5YR 5/6) masses of iron accumulation; few snail shell fragments; few fine rounded strongly cemented calcium carbonate nodules; moderately saline; exchangeable sodium percentage is 35; strongly effervescent; moderately alkaline; diffuse wavy boundary. (Thickness is 38 to 76 cm [15 to 30 in].)
BCknz--165 to 188 cm (65 to 74 in); light yellowish brown (10YR 6/4) clay, yellowish brown (10YR 5/4) moist; few fine faint brown (10YR 5/3) vertical streaks, weak medium subangular blocky structure parting to weak fine angular blocky; extremely hard, very firm, very sticky, very plastic; few very fine and fine roots; few fine rounded strongly cemented calcium carbonate nodules; few fine rounded clusters of crystals of gypsum and other salts; few fine and medium faint yellowish brown (10YR 5/6) and strong brown (7.5YR 5/6) masses of iron accumulation; moderately saline; exchangeable sodium percentage is 35; strongly effervescent; moderately alkaline.
TYPE LOCATION: La Salle County, Texas. From the intersection of U.S. Highway 81 and Texas Highway 97 in Cotulla, 0.8 mile east on Texas Highway 97 to Farm Road 624., 20 miles southeast on Farm Road 624, 2.75 miles south on county road, 1.55 miles east to gate at ranch headquarters, 1.3 miles east on ranch road to highline, 75 feet south along road under highline, 18 feet east in gulf cordgrass flat in rangeland. Caiman Creek, Texas USGS topographic quadrangle; Latitude: 28 degrees, 9 minute, 25.96 seconds N; Longitude: 99 degrees 1 minute, 5.56 seconds W.; NAD 83.
RANGE IN CHARACTERISTICS:
Soil moisture: An udic-ustic soil moisture regime. The soil moisture control section remains dry in some or all parts for 90 or more but less than 180 cumulative days in normal years. December through March are the driest months, while May and June are the wettest.
Solum thickness: 150 to more than 200 cm (60 to more than 80 in).
Horizontal variations of the soil surface within a pedon is 5 to 30 cm (2 to 12 in) expressed as gilgai microrelief. The soil cracks 1 to 7.5 (0.4 inch to 3 in) wide at the surface, when dry, and the cracks extend to a depth of more than 50 cm (20 in).
Electrical conductivity: (saturated paste extract) 0.2 to 4 dS/m in the upper 76 cm (30 in) and from about 4 to 16 dS/m below 76 cm (30 in).
Exchangeable sodium percentage is 15 or more in some part of the upper 76 cm (30 in) of the solum.
A horizon
Hue: 10YR
Value: 4 through 6
Chroma: 1 through 3
Texture: Clay
Clay content: 45 to 60 percent
Horizons with chroma of 1 are less than 10 inches thick
Bknss and Bknssz horizons
Hue: 10YR
Value: 5 through 7
Chroma: 2 and 3
Texture: Clay
Clay content: 45 to 60 percent
The B horizon has common to many streaks with colors of the A horizon
BCknz and C horizons (where present)
Colors: similar to the B horizon but usually of higher chroma or higher value.
Texture: Clay
Clay content: 45 to 60 percent
Mottles: fine to medium, faint to distinct, and brownish, grayish, or yellowish.
COMPETING SERIES: These are the
Arroyada,
Catarina,
Cotulla,
Lasalle, and
Montell series. Similar soils include the
Cochina,
Harlingen, and
Mercedes series.
Arroyada soils and Mercedes: have chroma of less than 1.5 in the upper 30 cm of their surface
Catarina soils: are moderately well drained, and formed in residuum or colluvium.
Cochina soils: have cracks that remain open for 90 to 150 days cumulative, have control sections with more than 60 percent clay and formed in residuum or colluvium
Cotulla, Harlingen, and Lasalle soils: have cracks that remain open for 90 to 150 days cumulative. Harlingen have control sections with more than 60 percent clay and formed in residuum or colluvium.
GEOGRAPHIC SETTING:
Parent Material: calcareous clayey alluvium
Landscape: inland, dissected coastal plain
Landform: floodplains of streams
Slope: 0 to 1 percent and are plane to slightly concave
Mean annual precipitation range: 508 to 610 mm (20 to 24 in)
Mean annual air temperature range: 21 to 23 degrees C (70 to 73 degrees F)
Frost-free period: 260 to 290 days
Elevation: 70 to 152 m (230 to 500 ft)
Thornthwaite annual P-E indices: 25 to 34
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Arroyada (TX),
Cochina (TX),
Cotulla (TX),
Maverick (TX),
Mercedes (TX) and
Montell (TX) series.
Arroyada soils: occur in flood plains
Cochina soils: occur in flood plains
Cotulla soils: occur on slightly higher elevations on uplands
Mercedes soils: occur on slightly higher elevations on uplands
Maverick soils: occur on slightly higher elevations on uplands and are moderately deep to claystone
Montell soils: occur on slightly higher elevations on uplands and have surfaces over 30 cm (12 in) thick with colors with chroma less than 1.5
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; ponded or very slow runoff; very slow permeability. Many small channels crisscross areas of this soil in all directions. These channels are mostly 30 to 76 cm (12 to 30 in) deep and 0.6 to 3 m (2 to 10 ft) wide at the top. They are 7 to 23 m (25 to 75 ft) apart.
USE AND VEGETATION: Rangeland. Native grasses are dominantly gulf cordgrass with some sacaton and buffalograss. Scattered woody species are mesquite (many branched and running types), retama and huisache. Spiny aster occurs along the main drainageways and along roads.
DISTRIBUTION AND EXTENT: Western Rio Grande Plain (MLRA 83B). The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: La Salle County, Texas; 1988.
REMARKS: This soil was formerly included in the Arroyada series.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: 0 to 13 cm (0 to 5 in). (A horizon)
Cambic horizon: 13 to 188 cm (5 to 74 in). (B horizons)
Vertic feature: The presence of slickensides at 13 to 165 cm (5 to 65 in). (Bknss and Bknssz horizons)
ADDITIONAL DATA: Local lab data on pedons from McMullen County.
TAXONOMIC VERSION: Keys to Soil Taxonomy, Eleventh Edition, 2010
National Cooperative Soil Survey
U.S.A.