LOCATION OSCAR OKEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, thermic Typic Natrustalfs
TYPICAL PEDON: Oscar silt loam--rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 5 inches; light brown (7.5YR 6/3) silt loam, dark brown (7.5YR 4/3) moist; weak fine platy structure in the upper part, massive in lower part; hard, friable; many pores; slightly acid; abrupt smooth boundary. (2 to 14 inches thick)
Btn-- 5 to 12 inches; reddish brown (5YR 4/3) silt clay loam, dark reddish brown (5YR 3/3) moist; moderate coarse prismatic structure parting to weak coarse blocky; hard, firm; clay films on faces of peds; patchy dark reddish brown (5YR 3/2) coatings on upper part and sides of peds; moderately alkaline; gradual smooth boundary. (6 to 30 inches thick)
BCn--12 to 24 inches; reddish brown (5YR 4/4) silty clay loam, dark reddish brown (5YR 3/4) moist; weak fine blocky structure; very hard, firm; few soft accumulations of calcium carbonate; calcareous; moderately alkaline; gradual smooth boundary. (4 to 20 inches thick)
C--24 to 60 inches; reddish brown (2.5YR 4/4) silty clay loam, dark reddish brown (2.5YR 3/4) moist; massive; hard, friable; strata of coarser textured material separated by bedding planes in the lower part; many soft accumulations and concretions of calcium carbonate; calcareous, moderately alkaline.
TYPE LOCATION: Jefferson County, Oklahoma; about 5 miles east and 1 mile north of Waurika; 50 feet north and 2,500 feet east of the southwest corner of sec. 26, T. 4. S., R. 7 W.
RANGE IN CHARACTERISTICS: Depth of soil is 60 inches or more. Thickness of solum ranges from 20 to more than 60 inches. Soft powdery secondary lime is within a depth of 60 inches.
The A horizon has hue of 5YR to 10YR, value of 4 to 7, and chroma of 2 to 4. Texture is silt loam, loam, or very fine sandy loam. Structure ranges from massive to weak fine platy or weak fine granular. Exchangeable sodium ranges from 0 to 75 percent. Electrical conductivity ranges from 0 to 16 mmhos/cm. Reaction ranges from moderately acid to moderately alkaline.
The Btn horizon has hue of 2.5YR to 2.5Y, value of 4 to 7, and chroma of 2 to 6. Texture is silt loam, silty clay loam, or clay loam. Clay content ranges from 24 to 35 percent. Structure is columnar, prismatic, or blocky. Exchangeable sodium ranges from 15 to about 80 percent and the electrical conductivity ranges from 4 to about 16 mmhos/cm. Reaction ranges from neutral to strongly alkaline.
The BCn or C horizon has hue of 2.5YR to 10YR, value of 4 to 6, and chroma of 2 to 6. Texture is silt loam, loam, silty clay loam, or clay loam. Clay content ranges from 24 to 35 percent. Exchangeable sodium and electrical conductivity are about the same as the Btn horizon. Reaction ranges from slightly to very strongly alkaline.
Some pedons have buried A or Bw horizons below 30 inches, but these are not diagnostic. Where present, hue is 5YR or 7.5YR, value of 4 or 5, and chroma of 2 to 4. Texture is silt loam, silty clay loam, or loam. Reaction ranges from neutral to moderately alkaline.
COMPETING SERIES: There are no series in the same family. Soils in similar families are Crot, Drummond, Pawhuska, and Wing series. Crot soils have more than 15 percent material that is coarser than very fine sand. Drummond, Pawhuska, and Wing soils have more than 35 percent average content in the upper 20 inches of the Bt horizon. Drummond and Pawhuska soils also have dark A1 horizon and Wing soils have 2 chroma mottles within 20 inches of the surface.
GEOGRAPHIC SETTING: Oscar soils are on flood plains that are occasionally flooded. Slope gradients are from 0 to 2 percent. Oscar soils occur in roughly circular areas from 20 to 100 feet in diameter. Oscar soils are formed in loamy alluvium that was either high in sodium or received additions of sodium after deposition. The climate is moist subhumid.
Mean Annual Precipitation: 26 to 40 inches;
Mean Annual Temperature: 58 to 64 degrees F.
Thornthwaite annual P-E index ranges from 44 to 64.
GEOGRAPHICALLY ASSOCIATED SOILS: These are McLain and Port series. McLain and Port soils lack natric horizons. In addition, McLain soils have an argillic horizon with a clay content of 35 percent or more and Port soils have mollic epipedons more than 20 inches thick.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow runoff; slow permeability.
USE AND VEGETATION: Used mainly for rangeland. The areas once cultivated have largely been returned to native grasses. Some areas are cultivated to small grains. The native vegetation is alkali sacation, switchgrass, blue grama, inland saltgrass, and dropseeds.
DISTRIBUTION AND EXTENT: Central Rolling Red Prairies of Oklahoma. Moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Jefferson County, Oklahoma; 1970.
REMARKS: Oscar soils were correlated as the Slickspots part of the Port-Slickpot complex in Comanche and Cotton Counties in Oklahoma. Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface of the soil to a depth of 5 inches (A horizon).
Natric horizon - the zone from 5 inches to a depth of 24 inches (Btn and BCn horizons).