LOCATION RIO DIABLO TX
Established Series
CLG:MLG:WJG
04/2011
RIO DIABLO SERIES
The Rio Diablo series consists of very deep, well drained, moderately slowly permeable soils that formed in calcareous alluvium from limestone hills. The soils are in valleys and on stream terraces and have slopes ranging from 0 to 3 percent.
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Aridic Haplustolls
TYPICAL PEDON: Rio Diablo silty clay--rangland. (Colors are for dry soil unless otherwise stated.)
A--0 to 17 inches; dark grayish brown (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; weak fine platy structure in upper one inch, weak fine subangular blocky structure parting to weak fine granular; hard, friable; common fine roots; few fine pores; few limestone pebbles; violently effervescent; moderately alkaline; clear wavy boundary. (10 to 20 inches thick)
Bw--17 to 29 inches; brown (7.5YR 5/4) clay, brown (7.5YR 4/4) moist; weak medium subangular blocky structure; hard, firm; few fine roots; few waterworn limestone pebbles, with thin coatings of secondary calcium carbonate; violently effervescent; moderately alkaline; gradual wavy boundary. (9 to 23 inches thick)
Bk1--29 to 46 inches; light brown (7.5YR 6/4) clay, brown (7.5YR 4/4) moist; weak fine subangular blocky structure; hard, firm; few fine roots; few threads and films of calcium carbonate; few waterworn limestone pebbles with thin coatings of secondary calcium carbonate; violently effervescent; moderately alkaline; gradual wavy boundary. (11 to 30 inches thick)
Bk2--46 to 60 inches; light brown (7.5YR 6/4) clay, brown (7.5YR 5/4) moist; weak fine subangular blocky structure; hard, firm; few fine roots in upper part; common soft masses and concretions of calcium carbonate comprising about 5 percent by volume; few waterworn limestone pebbles with thin coating of secondary calcium carbonate; violently effervescent; moderately alkaline.
TYPE LOCATION: Val Verde County, Texas; from the intersection of U. S. Highway 90 and Texas Highway 163 in Comstock, 48.7 miles north on Texas Highway 163 to ranch entrance; 2.65 miles east on ranch road; 0.3 mile northeast in range.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 60 to more than 80 inches. Depth to limestone or gravel ranges from 6 to 20 feet. Limestone fragments of pebble size range from 0 to 15 percent by volume. COLE ranges from 0.03 to 0.05. Clay content of the 10 to 40 inch control section ranges from 40 to 55 percent and silicate clay ranges from 35 to 45 percent. Calcium carbonate equivalent of the 10 to 40 inch control section ranges from 20 to 40 percent with 0 to 5 percent in visible secondary forms.
The A horizon has hue of 10YR or 7.5YR, chroma of 3 to 5 and value of 2 or 3. Texture is silty clay loam, silty clay, or clay.
The Bw and Bk horizon has hue of 7.5YR, or 10YR, chroma of 5 to 7 and value of 3 or 4. Texture is silty clay loam, silty clay, or clay. Visible segregations of lime comprise less than 5 percent of any B horizon having its upper boundary within 40 inches of the surface. Bk horizons with upper boundaries below 40 inches contain 5 to 20 percent visible segregations of lime. Some pedons have gravelly or cobbly strata below 40 inches.
COMPETING SERIES: There are no competing series in the same family. Similar soils include the
Angelo,
Frio,
Iraan,
Knippa,
Nipsum,
Paloduro,
Rioconcho, and
Zita series. Angelo and Knippa soils have a calcic horizon within 40 inches. In addition, Angelo and Knippa soils as well as Rioconcho soils have a
Cole of more than 0.7 percent. Frio, Iraan, and Nipsum soils have mollic epipedons more than 20 inches thick. Iraan soils also have fine-silty control sections. Paloduro and Zita soils both have fine-loamy control sections and Zita soils have noncalcareous A horizons.
GEOGRAPHIC SETTING: Rio Diablo soils are in nearly level to gently sloping valleys on stream terraces. Slopes are plane and gradients are generally less than 1 percent, but range up to 3 percent. The soil formed in fine textured, calcareous alluvium from limestone. Climate is semiarid. Mean annual precipitation ranges from 15 to 22 inches; P-E indices are 26 to 34, and mean annual temperature ranges from 66 degrees to 70 degrees F. Frost free days range from 230 to 290 days. Elevation ranges from 1500 to 2300 feet.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Dev,
Ector,
Kavett, and
Tarrant series. Dev soils are loamy-skeletal, have a mollic epipedon more than 20 inches thick and are on commonly flooded bottomlands. Ector and Tarrant soils are shallow soils of gently undulating to hilly uplands and both have loamy-skeletal control sections. Kavett soils are less than 20 inches thick over a petrocalcic horizon.
DRAINAGE AND PERMEABILITY: Well drained. Runoff on 0 to 1 percent slopes is negligible and very low on 1 to 3 percent slopes. Permeability is moderately slow.
USE AND VEGETATION: Most of the areas of Rio Diablo soils are used as range. In good and excellent range condition it is dominated by sideoats grama, cane bluestem, Arizona cottontop, plains bristlegrass, Canada wildrye, and Texas wintergrass. As retrogression occurs, perennial threeawn, slim tridens, tobosa, buffalograss and curly mesquite increase along with woody shrubs. As deterioration continues, a large percent of the plants consists of woody shrubs such as mesquite, juniper, agarito, tasajillo, and other cacti with an understory of red grama, hairy tridens, perennial threeawn, and scattered areas of tobosa. Some areas of these soils are irrigated for the production of improved pasture grasses.
DISTRIBUTION AND EXTENT: The Western Edwards Plateau of Texas. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Val Verde County, Texas; 1979.
REMARKS: The soils were formerly included in the Knippa series.
Diagnostic features and horizons recognized in this pedon are:
Mollic epipedon - 0 to 17 inches
Cambic horizon - 17 to 46 inches
Calcic horizon - 46 to 60 inches
National Cooperative Soil Survey
U.S.A.