LOCATION AGAN OKEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, thermic Udertic Paleustalfs
TYPICAL PEDON: Agan loam, on convex slope--abandoned cropland. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 7 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; weak fine granular; hard, friable; few fragments of granite less than 3 inches in diameter; slightly acid; abrupt wavy boundary. (3 to 10 inches thick)
Bt1--7 to 26 inches; grayish brown (10YR 5/2) clay, very dark grayish brown (10YR 3/2) moist; common fine faint brown redoximorphic concentrations; moderate medium blocky structure; extremely hard, very firm; few fine roots and pores; thick continuous clay films on surfaces of peds; surfaces on vertical peds have thin coatings of material from A horizon; few fragments of granite less than 3 inches in diameter; neutral; gradual wavy boundary. (7 to 34 inches thick)
Bt2--26 to 46 inches; grayish brown (10YR 5/2) clay, dark grayish brown (10YR 4/2) moist; common fine faint brown redoximorphic concentrations; weak medium blocky structure; extremely hard, very firm; few fine roots and pores; thick continuous clay films on surface of peds; some vertical faces are coated with material from A horizon; about 5 percent by volume fragments of granite less than 3 inches in diameter; slightly alkaline; gradual wavy boundary. (0 to 34 inches thick)
Bt3--46 to 61 inches; grayish brown (2.5Y 5/2) gravelly clay, dark grayish brown (2.5Y 4/2) moist; common medium distinct brown (10YR 4/3) redoximorphic concentrations; weak coarse blocky structure; extremely hard, very friable; continuous clay films on surfaces of peds; about 25 percent by volume fragments of granite less than 3 inches in diameter; moderately alkaline; gradual wavy boundary. (0 to 30 inches thick)
BC--61 to 84 inches; light brownish gray (2.5Y 6/2) very gravelly clay in upper part and weathered granite in lower part; very weak blocky structure; extremely hard, very firm; 60 to 90 percent by volume fragments of granite less than 3 inches in diameter; moderately alkaline.
TYPE LOCATION: Johnston County, Oklahoma, about 7 miles north of Tishomingo; about 2,300 feet west and 200 feet north of the southeast corner of sec. 33, T. 2 S., R. 6 E.
RANGE IN CHARACTERISTICS: Solum thickness and depth to weathered granite bedrock ranges from 60 to more than 72 inches.
The A or Ap horizon has hue of 10YR, value of 4 or 5, and chroma of 1 or 2. It is loam or silt loam and ranges from moderately acid to neutral. Granitic fragments less than 3 inches in diameter range from 0 to 10 percent by volume.
The Bt1 and Bt2 horizon has hue of 10YR, value of 4 to 6, and chroma of 1 to 3, or hue of 2.5Y, value of 4 to 6, and chroma of 2, or a matrix that has redoximorphic concentrations and depletions in the lower part in shades of gray, brown, or yellow. These horizons are clay, silty clay, or gravelly clay and ranges from slightly acid to mildly alkaline. Granitic fragments less than 3 inches in diameter range from 0 to 30 percent by volume.
The Bt3 horizon has hue of 10YR, value of 4 to 6, and chroma of 1 to 4, or hue of 2.5Y, value of 4 to 6, and chroma of 2, or it has redoximorphic concentrations and depletions in shades of gray, brown, or yellow. It is gravelly clay, gravelly clay loam, or gravelly sandy clay and ranges from neutral to moderately alkaline. Granitic fragments less than 3 inches in diameter range from 15 to 30 percent by volume.
The BC horizon has the colors of the Bt3 horizon. In some pedons it has redoximorphic concentrations and depletions in shades of pink, gray, brown, or yellow in hue of 7.5YR, 10YR, or 2.5Y, or it is mottled in these colors. It is very gravelly or extremely gravelly counterparts of clay, clay loam, sandy clay, or sandy clay loam, and ranges from slightly to moderately alkaline. Granitic fragments range from 40 to 90 percent by volume. About 35 to 75 percent by volume of these fragments are less than 3 inches in diameter, and about 5 to 15 percent by volume are 3 to 10 inches in diameter.
COMPETING SERIES: These are the Aydelotte series in the same family. Aydelotte soils have hues redder than 7.5YR in the Bt horizon and do not have perched water tables.
GEOGRAPHIC SETTING: These smooth, nearly level or slightly convex very gently sloping soils are on uplands in the Grand Prairies. They formed in material weathered from granite. Slope gradients range from 0 to 3 percent. The climate is subhumid. Average annual temperature ranges from 62 to 64 degrees F., mean annual precipitation ranges from 38 to 40 inches, and Thornthwaite P-E indices range from 60 to 64. Frost free days range from 210 230. Elevation ranges from 500 to 1000 feet.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Chigley series and the Durant, Ravia, and Stephenville series. These soils are higher in elevation. Durant and Ravia soils have a mollic epipedon. Stephenville soils have a fine-loamy control section.
DRAINAGE AND PERMEABILITY: Moderately well drained; runoff is high on 0 to 1 percent slopes and very high on 1 to 3 percent slopes; very slow permeability.
USE AND VEGETATION: Used as range and pasture. Many areas were formerly cultivated but are now abandoned. Native vegetation consists of big bluestem, little bluestem, switchgrass, and indiangrass.
DISTRIBUTION AND EXTENT: In the Grand Prairie of Oklahoma and possibly Texas. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Johnston County, Oklahoma; 1975.
REMARKS: Soil Interpretation Record: Series OK0025
Diagnostic horizons and features in this pedon are:
Ochric epipedon - zone from the surface to about 7 inches (Ap horizon)
Argillic horizon - zone from 7 to 61 inches. (Bt1, Bt2, Bt3 horizons)
Udertic features - soils that have cracks at some period in most years that are 1 cm or more wide at a depth of 20 inches, that are at least 12 inches long in some part, and extend upward to the surface or base of the Ap horizon, and have a COLE of 0.07 or more in the upper 20 inches of the Bt horizon and a potential linear extensibility of 6 cm or more in the upper 50 inches of the soil; have more than 35 percent clay in the Bt horizons; and the depth to soft powdery secondary lime is more than 28 inches.
Paleustalfs features - soils that have an ustic moisture regime; have an ochric epipedon; have an argillic horizon and have base saturation of 35 percent or more at a depth of 72 inches below the soil surface; have an argillic horizon in which the upper part has a clayey particle-size class and there is an increase of at least 15 percent clay (absolute) within a vertical distance of 1 inch at the upper boundary or have an argillic horizon that has a clay distribution such that the percentage of clay does not decrease by as much as 20 percent of the maximum within a depth of 60 inches from the soil surface and has common coarse redoximorphic concentrations in the lower part of the argillic horizon.