LOCATION KNOLLE TXEstablished Series
TAXONOMIC CLASS: Fine-loamy, siliceous, superactive, thermic Ultic Haplustalfs
TYPICAL PEDON: Knolle coarse sand on a convex 4.5 percent slope in pasture. (Colors are for dry soils unless otherwise stated.)
Ap--0 to 8 inches; grayish brown (10YR 5/2) coarse sand; very dark grayish brown (10YR 3/2) moist; weak coarse angular blocky structure; soft, very friable, nonsticky and nonplastic; many fine roots, few krotovinas; slightly acid; clear smooth boundary. (3 to 14 inches thick)
Bt1--8 to 12 inches; grayish brown (10YR 5/2) loamy coarse sand; very dark grayish brown (10YR 3/2) moist; weak coarse angular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many fine roots; common fine pores; thin faint clay films on surfaces of peds; slightly acid; gradual smooth boundary.
Bt2--12 to 26 inches; yellowish red (5YR 4/6) sandy clay loam, yellowish red (5YR 4/6) moist; weak medium subangular blocky structure; hard, friable, sticky and plastic; common fine roots; common fine pores; thick clay films on surfaces of peds; common medium prominent dark brown (7.5YR 4/2) iron depletions; moderately acid; gradual smooth boundary.
Bt3--26 to 34 inches; yellowish red (5YR 4/6) sandy clay loam, yellowish red (5YR 4/6) moist; with coatings on peds of dark brown (7.5YR 4/2); weak medium subangular blocky structure; hard, friable, sticky and plastic; few roots; few fine pores; thick clay films on surfaces of peds; strongly acid; gradual smooth boundary. (combined thickness of Bt horizons is 15 to 50 inches)
BCt--34 to 46 inches; yellowish red (5YR 5/8) sandy clay loam; yellowish red (5YR 4/8) moist; weak medium subangular blocky structure; slightly hard, friable, sticky and plastic; few patchy clay films on faces of peds; moderately acid; gradual smooth boundary. (0 to 20 inches thick)
C--46 to 62 inches; strong brown (7.5YR 5/6) sandy loam; strong brown (7.5YR 5/6) moist; massive; hard, friable; medium acid.
TYPE LOCATION: Washington County, Texas; about 12 miles northeast of Brenham; from intersection of Texas Highway 105 and Farm Road 2193; 3.5 miles east on Texas 105; 1 mile south on county road; then 100 feet east of road.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 40 to 60 inches. Weighted average of the clay content of the control section ranges from 20 to 35 percent.
The Ap horizon has hue of 10YR, value of 3 to 5, and chroma of 2 or 3. Texture is coarse sand, sand, fine sand or loamy sand. Clay content ranges from 2 to 15 percent. Reaction ranges from medium acid to neutral.
The Bt1 horizon has hue of 10YR, value of 3 to 5, and chroma of 2 or 3. Texture ranges from sandy loam to loamy coarse sand and loamy sand. Reaction ranges from strongly acid to neutral.
The Bt2 and Bt3 horizons have matrix colors in hue of 7.5YR or 5YR, value of 4 or 5, and chroma of 3 to 6. They contain common or many redoximorphic features of these colors, and brown, dark brown, and dark grayish brown. Texture is sandy clay loam, clay loam or sandy clay with clay content ranging from 20 to 40 percent but averaging 20 to 35 percent in the upper 20 inches of the argillic. Reaction ranges from strongly acid to neutral.
The BCt horizon, where present, has hue of 5YR and 7.5YR, value of 5 or 6, and chroma of 6 or 8. Redoximorphic features range from none to common in these colors and brownish yellow and yellowish brown. Texture is sandy clay loam, loam, or sandy loam. Reaction ranges from strongly acid to slightly acid.
The C horizon has hue of 7.5YR, value of 5 or 6, and chroma of 6 or 8. Texture ranges from sandy clay loam to loamy sand. Reaction ranges from strongly acid to slightly acid.
COMPETING SERIES: These are the Littleaxe (OK), Minerva (TX), Stephenville (OK), and Weatherford (TX) series. Similar soils are the Hye, Klump, Konawa, Konsil, and Silawa series. Littleaxe soils have a paralithic contact between 40 and 60 inches. Minerva soils have sola more than 60 inches thick. Stephenville soils have sandstone bedrock within 40 inches. Weatherford soils do not have dark coatings on the surfaces of peds in the argillic horizon. Hye and Konawa soils have mixed mineralogy. Klump soils have a mollic epipedon. Konsil soils have an argillic horizon that does not decrease in clay content within 60 inches. Silawa soils have argillic horizons with slightly redder hue, do not have brownish iron depletions and are in the semiactive family.
GEOGRAPHIC SETTING: Knolle soils are on convex gently sloping to sloping uplands. They formed in materials weathered from sandstone mainly of Miocene Age. Slopes are mainly 2 to 5 percent but range from 1 to 8 percent. Mean annual precipitation ranges from 35 to 45 inches with dry summer seasons. Mean annual temperature ranges from 64 to 70 degrees F. Frost free days range from 260 to 280 days and elevation ranges from 200 to 500 feet. Thornthwaite annual P-E indices range from 48 to 64.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Klump series and the Bleiblerville, Cuero, and Frelsburg series. Bleiblerville and Frelsburg soils are on nearby landscapes and have intersecting slickensides. Cuero soils have mollic epipedons more 20 inches thick and are on footslopes and concave areas. Klump soils are on sideslopes of nearby areas.
DRAINAGE AND PERMEABILITY: Knolle soils are well drained. Permeability is moderate. Runoff is very low on 1 to 3 percent slopes, low on 3 to 5 percent slopes, and medium on 5 to 8 percent slopes.
USE AND VEGETATION: Used mainly for improved pasture. Very few areas support woody vegetation. Native grasses were mainly little bluestem, indiangrass, sideoats grama, and annual grasses, with some pricklypear and bullnettle.
DISTRIBUTION AND EXTENT: Southeast central Texas. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Washington County, Texas, 1978.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - 0 to 8 inches. (dark colored A horizon, but less than 1 percent organic matter)
Argillic horizon - 8 to 46 inches (Bt and BCt horizons)
Ultic feature - base saturation less than 75 percent throughout the argillic horizon.
ADDITIONAL DATA: S76TX-477-003 (NSSL 76PO747 - 76PO752).