LOCATION RIOCONCHO TXEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Vertic Haplustolls
TYPICAL PEDON: Rioconcho clay loam--rangeland. (Colors are for dry soil unless otherwise stated).
A1--0 to 14 inches; dark grayish brown (10YR 4/2) clay loam, very dark brown (10YR 2/2) moist; weak fine granular and moderate very fine subangular blocky structure; hard, firm, but crushes easily to granules, sticky, and plastic; many fine roots; few fine pores; few wormcasts; strongly effervescent; moderately alkaline; gradual wavy boundary. (6 to 24 inches thick)
A2--14 to 36 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium angular blocky structure; very hard, firm, but crushes easily to granules, sticky, and plastic; few fine roots, few fine pores and wormcasts; strongly effervescent; moderately alkaline; diffuse wavy boundary. (10 to 50 inches thick)
Bk--36 to 80 inches; light brown (7.5YR 6/4) clay loam; brown (7.5YR 5/4) moist; weak fine angular blocky structure; very hard, friable, sticky, and plastic; few fine roots; patchy thin coatings of calcium carbonate on surfaces of peds, and threads of calcium carbonate in pores above 70 inches; strongly effervescent; moderately alkaline.
TYPE LOCATION: Tom Green County, Texas; about 10 miles northwest of San Angelo on U.S. Highway 87, then 1.5 miles south on Texas Highway 2288, then 0.1 mile east in range.
RANGE IN CHARACTERISTICS: Solum thickness is more than 80 inches. Depth to limestone, gravel, or sand ranges from 6 to 20 feet. Texture is clay loam, silty clay loam, clay, or silty clay. Clay content ranges from 35 to 55 percent. Limestone fragments and quartz fragments of pebble and cobble size range from 0 to 15 percent by volume. When the soil is dry, cracks 0.5 to 1 inch wide extend to depths of 20 to 30 inches. COLE ranges from 0.07 to 0.21. Linear extensibility is greater than 6 cm in the upper 40 inches. Calcium carbonate equivalent ranges from 5 to about 30 percent. Reaction is slightly alkaline or moderately alkaline. Organic carbon has an irregular distribution with depth.
The A horizon has hue of 7.5YR or 10YR, value of 3 to 5, and chroma of 1 to 3. Moist color values are 1 to 2 units lower. The A1 horizon ranges from noneffervescent to strongly effervescent. Some pedons have Bw horizons below 24 inches.
The Bk horizon has hue of 7.5YR or 10YR, value of 5 to 7, and chroma of 2 to 4. Below 40 inches this horizon in some pedons, has strata that contain as much as 20 to 40 percent pebble and stone sized fragments of limestone, quartz, and caliche.
COMPETING SERIES: This is the Teagard is the series. Similar soils are the Cameron, Frio, Gageby, Garvin, Krum, Olmito, and Raymondville series. Teagard soils are moderately deep to a paralithic contact, and developed in residuum derived from shale. Cameron, Olmito, and Raymondville soils are in the hyperthermic family. Frio soils have a COLE less than 0.07. Gageby soils are in the fine-loamy family. Krum and Nukrum soils have a regular decrease in organic carbon with depth. Garvin soils are moist for longer periods of time in the moisture control section. In addition Garvin soils have smectitic mineralogy.
GEOGRAPHIC SETTING: Rioconcho soils are on nearly level flood plains of streams that carry clayey and limy sediments. Slopes are dominantly less than 1 percent but some are as much as 2 percent. Some of these areas are protected by dams and no longer flood. Mean annual temperature ranges from 58 to 68 degrees F., and mean annual precipitation ranges from 15 to 26 inches. Frost-Free days range from 210 to 240, and elevation ranges from 1,400 to 2,500 feet. Thornthwaite P-E indices range from 24 to 38.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Angelo, Dev, Lipan, Spur, and Tulia series. Angelo soils have calcic horizons at depths of less than 40 inches. Dev soils are in the loamy-skeletal family, and have carbonatic mineralogy. Lipan soils have slickensides. Spur and Tulia soils are in the fine-loamy family. In addition, Tulia soils have ochric epipedons.
DRAINAGE AND PERMEABILITY: Moderately well drained. Permeability is slow. Runoff is low on 0 to 1 percent slopes and medium on 1 to 2 percent slopes. Flooding occurs at intervals ranging from 1 or more times a year to once in 20 years.
USE AND VEGETATION: Mainly cultivated and used for growing cotton, grain sorghum, wheat, and oats. Some areas are used as rangeland. Native vegetation includes buffalograss, Texas wintergrass, vine mesquite, mesquite, hackberry, and pecan.
DISTRIBUTION AND EXTENT: The Rolling Plains and Edwards Plateau of Texas. The series is extensive.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Tom Green County, Texas; 1971.
REMARKS: The soils were formerly included in the Frio series.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 36 inches. (A1 and A2 horizons)
Cambic horizon - 36 to 80 inches. (Bk horizon, does not have enough carbonates to be a calcic.)
Fluventic feature - irregular decrease in organic matter.
Vertic Feature - Linear extensibility exceeds 6 cm within 40 inches of the surface, and the soil has cracks greater than 5 mm that extend from the surface to greater than 20 inches.
Soil Interpretation Record Nos.: TX0087; DRY TX1167