LOCATION DARST TXEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, thermic Ultic Paleustalfs
TYPICAL PEDON: Darst very gravelly sandy loam - native rangeland.
(Colors are for dry soil unless otherwise stated.)
A--0 to 5 inches; brown (10YR 5/3) very gravelly sandy loam, dark brown (10YR 4/3) moist; weak fine granular structure; hard, friable; common fine roots; an estimated 65 percent by volume of siliceous pebbles 0.25 to 3 inches in diameter; medium acid; clear smooth boundary. (2 to 7 inches thick)
E--5 to 8 inches; yellowish brown (10YR 5/4) very gravelly sandy loam, dark yellowish brown (10YR 4/4) moist; weak fine granular structure; hard, friable; few fine roots; pebble content same as horizon above; medium acid; abrupt smooth boundary. (2 to 5 inches thick)
Bt1--8 to 22 inches; red (2.5YR 4/6) clay, dark red (2.5YR 3/6) moist; moderate fine and medium blocky structure; very hard, firm; few fine roots; few fine pores; thick clay films on faces of peds and in pores; very strongly acid; gradual smooth boundary. (10 to 16 inches thick)
Bt2--22 to 30 inches; red (2.5YR 5/6) clay, red (2.5YR 4/6) moist; few fine prominent brownish yellow mottles; moderate fine blocky structure; very hard, firm; few fine roots; few fine pores; thick clay films on faces of peds and in pores; very strongly acid; gradual smooth boundary. (6 to 12 inches thick)
Bt3--30 to 37 inches; red (2.5YR 5/6) sandy clay, red (2.5YR 4/6) moist; few fine prominent brownish yellow and pale brown mottles; weak fine blocky structure; very hard, firm; few fine roots; few fine pores; few clay films on faces of peds and in pores; very strongly acid; clear smooth boundary. (0 to 7 inches thick)
Cr--37 to 50 inches; reddish yellow (7.5YR 6/6) mudstone, strong brown (7.5YR 5/6) moist; massive; extremely hard, very firm; thin discontinuous interbedded layers of strongly cemented sandstone; very strongly acid.
TYPE LOCATION: Guadalupe County, Texas; about 7 miles south of Kingsbury, Texas, on Farm Road 1104; 0.8 mile southeast on gravel road; 100 feet into wooded pasture west of road.
RANGE IN CHARACTERISTICS: Solum thickness is 20 to 40 inches. A few sandstone and siliceous cobbles are on the surface of some pedons.
The A1 horizon is dark brown (10YR 4/3; 7.5YR 4/2), brown (10YR 5/3; 7.5YR 5/4), yellowish brown (10YR 5/4), or dark yellowish brown (10YR 4/4). The E horizon is generally 1 to 2 units of value and chroma higher than the A horizon. The A and E horizons are gravelly or very gravelly sandy loam or loamy sand and their nongravelly counterparts. Siliceous pebbles and sandstone fragments, mainly less than 3 inches in diameter, comprise up to 70 percent by volume. Thickness is 4 to 12 inches. These horizons are slightly acid or medium acid.
The B horizon is red (2.5YR 4/6, 4/8, 5/6, 5/8), yellowish red (5YR 4/6, 4/8, 5/6, 5/8), reddish brown (5YR 4/4, 5/4), or light reddish brown (5YR 6/4). Moist values are 4 or more in some part of each pedon. Mottles in shades of gray, brown, or yellow are in the lower Bt horizon of some pedons. Mottles with chromas of 2 or less, where present, are at depths of 30 to 40 inches. Reaction is medium acid, strongly acid, or very strongly acid. The Bt1 and Bt2 horizons are clay or sandy clay with clay content of 35 to 55 percent. Siliceous and sandstone pebbles comprise 0 to 15 percent by volume. The Bt3 horizon is sandy clay or sandy clay loam.
The Cr horizon is reddish, brownish, or yellowish acid, massive siltstone or soft mudstone.
COMPETING SERIES: These include the Birome, Bonti, Castell, Cona, Jedd, Rosanky, Shatruce and Travis series. Birome soils are 20 to 40 inches thick over gneiss. Cona and Shatruce soils formed over shaly and clayey sediments. Jedd soils have Bt horizons less than 16 inches thick. Rosanky and Travis soils have sola more than 40 inches thick.
GEOGRAPHIC SETTING: Darst soils are on convex upland ridges. Slope gradients are mainly 5 to 12 percent, but range from 2 to 20 percent. The soil formed in residuum from massive siltstone or soft mudstone. Gravel on the surface and in the A horizon is presumed to be lag gravel from the Uvalde formation. The climate is moist subhumid with a mean annual precipitation of 28 to 38 inches. The P-E indices are 44 to 66. Average annual temperature is about 67 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Jedd and Rosanky series and the Crockett and Vernia series. Jedd soils occur at slightly higher elevations and Rosanky soils occur near the crest of upland areas. Crockett soils have higher base status in the Bt horizon and are more than 40 inches thick. Crockett soils occur at lower elevations. Vernia soils occur at the crests of ridges at slightly higher elevations.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderately slow permeability.
USE AND VEGETATION: Mainly used for rangeland. Vegetation includes post oak and blackjack oak trees with an understory of bluestems and annual grasses and weeds.
DISTRIBUTION AND EXTENT: Mainly in central Texas. The series is of minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Guadalupe County, Texas; 1973.
REMARKS: These soils formerly were included with the Bonti series.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - 0 to 8 inches.
Argillic horizon - 8 to 30 inches.
Abrupt texture change - at 8 inches.