LOCATION OBARO              TX+KS OK

OBARO SERIES

TAXONOMIC CLASS: Fine-silty, mixed, superactive, thermic Typic Haplustepts

TYPICAL PEDON: Obaro loam, on east-facing, convex, 2 percent slope in rangeland at an elevation of about 2,120 feet. (Colors are for dry soil unless otherwise stated.)

A--0 to 8 inches; reddish brown (5YR 5/4) loam, dark reddish brown (5YR 3/4) moist; weak subangular blocky structure; slightly hard, very friable; many roots; few calcium carbonate coated sandstone fragments on surface and within horizon; strongly effervescent; moderately alkaline; clear smooth boundary. (5 to 12 inches thick)

Bw--8 to 18 inches; reddish brown (2.5YR 5/4) loam, dark reddish brown (2.5YR 3/4) moist; weak prismatic structure parting to moderate medium subangular blocky; slightly hard, very friable; many fine roots; many fine pores; common wormcasts; about 3 percent of less than 1 inch in diameter pararock fragments consisting of weakly to moderately cemented sandstone; few films and threads of calcium carbonate; violently effervescent; moderately alkaline; gradual smooth boundary. (8 to 22 inches thick)

Bk--18 to 30 inches; light red (2.5YR 6/6) loam, red (2.5YR 4/6) moist; compound, weak prismatic structure parting to moderate medium subangular blocky; hard, very friable; few roots; less than 1 inch in diameter pararock fragments consisting of weakly to moderately cemented sandstone; few films and masses of calcium carbonate and few carbonate coatings on sandstone fragments; violently effervescent; moderately alkaline; clear smooth boundary. (4 to 14 inches thick)

Cr--30 to 60 inches; red (2.5YR 5/6) weakly cemented calcareous sandstone, dark red (2.5YR 3/6) moist; common fine distinct bluish green mottles.

TYPE LOCATION: Kent County, Texas; From the intersection of Texas Highway 208 and U.S. Highway 380 in Clairmont, 2.6 miles east of Clairemont on U.S. Highway 380, 2.1 miles north on ranch road, then 50 feet east in rangeland; Latitude: 33 degrees, 11 minutes, 16 seconds N; Longitude: 100 degrees, 42 minutes, 30 seconds W; Clairmont East, Texas USGS quad; NAD 27.

RANGE IN CHARACTERISTICS:
Soil moisture: An ustic moisture regime. The soil moisture control section is dry in some or all parts for more than 90 but less than 180 days, cumulative, in normal years. July through August and December through February are the driest months. These soils are intermittently moist in September through November and March through June.
Mean annual soil temperature: 61 to 65 degrees F.
Depth to paralithic contact: 20 to 30 inches
Depth to secondary carbonates: 10 to 20 inches
Depth to cambic horizon: 5 to 12 inches
Solum thickness: 20 to 30 inches.
Particle-size control section: 18 to 35 percent silicate clay

A horizon:
Hue: 5YR or 7.5YR
Value: 4 or 5 dry, 3 to 5 moist
Chroma: 3 or 4
Texture: loam, very fine sandy loam, clay loam, silt loam, and silty clay loam
Visible calcium carbonate: 0 to 5 percent as threads, masses, and nodules.
Calcium carbonate equivalent: 0 to 15 percent by weight.
Effervescence: strong or violent
Reaction: slightly or moderately alkaline

Bw horizon:
Hue: 2.5YR or 5YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 4 to 6
Texture: loam, very fine sandy loam, clay loam, silt loam, and silty clay loam
Pararock fragments: 0 to 10 percent of weakly cemented sandstone.
Secondary calcium carbonate: 0 to 5 percent in the form of threads, masses, and nodules.
Effervescence: strong or violent
Reaction: slightly or moderately alkaline

Bk horizon:
Hue: 2.5YR or 5YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 4 to 6
Texture: loam, very fine sandy loam, clay loam, silt loam, and silty clay loam
Pararock fragments: 2 to 6 percent of weakly cemented sandstone.
Visible carbonate equivalent: 2 to 35 percent in the form of films, threads, and masses.
Effervescence: violent
Reaction: slightly or moderately alkaline

Cr horizon:
Hue:2.5 YR or 5 YR
Value 4 to 6
Chroma 4 to 6
Ranges from weakly to moderately cemented calcareous sandstone or siltstone.

COMPETING SERIES: These are the Aspermont and Lamar series. Similar soils include the Enterprise, Lutie, Owens, Throck, Vernon, Weymouth, and Woodward series.
Aspermont and Lamar series: do not have sandstone within 40 inches and Lamar series has hues of 10YR and 2.5Y.
Enterprise and Woodward series: have less than 18 percent silicate clay in the particle-size control section.
Lutie series: has dark A horizons with moist values and chromas of less than 3.5.
Owens, Throck, and Vernon series: have greater than 35 percent silicate clay in the particle-size control section.

GEOGRAPHIC SETTING:
Parent material: residuum of weakly to moderately cemented, fine-grained calcareous sandstones, primarily of Permian age.
Landform: on knolls, ridges, and on side slopes of erosional surfaces in the Central Rolling Red Plains.
Slopes: 1 to 15 percent.
Mean annual air temperature: 59 to 63 degrees F.
Mean annual precipitation: 20 to 24 inches.
Frost-free period: 185 to 220 days.
Elevation: 1,800 to 3,000 feet.
Thornthwaite annual P-E Index Values: 26 to 36.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Aspermont series, the similar Enterprise and Weymouth series, and the Carey, Miles, and Quinlan series.
The Aspermont, Enterprise and Weymouth soils are on slightly higher landscape positions.
Carey series: is on slightly higher landscape positions and has a mollic epipedon and argillic horizon.
Miles series: is on higher landscape positions and has an argillic horizon.
Quinlan series: is on similar landscape positions and has sandstone within 20 inches of the soil surface.

DRAINAGE AND PERMEABILITY: Well drained. Moderate permeability. Surface runoff is very low on 1 to 3 percent slopes, low on 3 to 5 percent slopes, and medium on 5 to 15 percent slopes.

USE AND VEGETATION: Primarily used as native rangeland but areas on lesser slopes are cultivated to cotton, small grains, and grain sorghum. Native grasses are blue grama, sand dropseed, sideoats grama, and buffalograss. Scattered mesquite trees grow in some areas. This soil has been correlated to the Loamy Prairie (078BY081TX)) range site in Texas.

DISTRIBUTION AND EXTENT: West central Texas and possibly southwestern Oklahoma (sub-MLRA-78B). The series is extensive.

MLRA OFFICE RESPONSIBLE: Temple, Texas

SERIES ESTABLISHED: Stonewall County, Texas; 1970.

REMARKS: Series revised MLRA-77 Soil Survey; Floyd County, Texas. Obaro soils were formerly included in the Woodward series and were last revised 1/86.

Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon: 0 to 8 inches. (A horizon)
Cambic horizon: 8 to 18 inches. (Bw horizon)
Paralithic contact: occurs at 30 inches.

Soil interpretations record: TX0325

Taxonomic version: Keys to Soil Taxonomy, Eighth Edition, 1998.