LOCATION KEOKUK             OK

KEOKUK SERIES

TAXONOMIC CLASS: Coarse-silty, mixed, superactive, thermic Fluventic Haplustolls

TYPICAL PEDON: Keokuk silt loam--cultivated. (Colors are for dry soil unless otherwise stated.)

Ap--0 to 12 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 3/2) moist; moderate fine granular structure; hard, very friable; slightly acid; gradual smooth boundary. (7 to 18 inches thick)

Bw--12 to 24 inches; brown (7.5YR 5/2) silt loam, brown (7.5YR 4/2) moist; weak medium subangular blocky structure; slightly hard, very friable; slightly alkaline; gradual smooth boundary. (8 to 26 inches thick)

C--24 to 65 inches; light brown (7.5YR 6/4) very fine sandy loam, brown (7.5YR 5/4) moist; massive; slightly hard, very friable; stratified with a few layers of silt loam, loam, and loamy very fine sand that are 1/4 inch to 3 inches thick; few films of secondary carbonates at a depth of 29 inches; calcareous; moderately alkaline.

TYPE LOCATION: Pottawatomie County, Oklahoma; about 6 miles east and 6 miles north of Shawnee; 1,850 feet east and 200 feet south of the northwest corner of sec. 29. T. 11 N., R. 5 E.

RANGE IN CHARACTERISTICS: Solum thickness ranges from 18 to 44 inches. Depth to secondary carbonates is 10 to 35 inches.

The Ap or A horizon has hue of 5YR or 10YR, value of 4 or 5, and chroma of 2 or 3. Texture is silt loam, loam, or very fine sandy loam. Reaction ranges from slightly acid to moderately alkaline.

The Bw horizon has hue of 2.5YR to 10YR, value of 4 to 6, and chroma of 2 to 8. Texture and reaction is the same as the A horizon.

The C horizon has hue of 2.5YR to 10YR, value of 4 to 7, and chroma of 2 to 8. Texture is stratified silt loam, loam, very fine sandy loam, and loamy very fine sand. Reaction is slightly or moderately alkaline. Buried soils occur in some pedons below 50 inches.

COMPETING SERIES: Lugert series is the only soil in this family. Soils in similar families are Asa, Asher, Lamkin, Loco, Lucien, Minco, Nash, Pocasset, and Reinach series. Lugert soils are dry for longer periods. Asa, Asher, and Lamkin soils have a fine-silty control section. Loco and Lucien soils are underlain with a paralithic sandstone bedrock between depths of 10 to 20 inches. Minco and Nash soils have secondary carbonates deeper than 36 inches. In addition, Nash soils are underlain with a paralithic sandstone bedrock between depths of 20 to 40 inches. Pocasset soils have a coarse-loamy control section. Reinach soils have a mollic epipedon more than 20 inches thick.

GEOGRAPHIC SETTING: Keokuk soils are on nearly level flood plains in the Central Rolling Red Prairies. Slopes are 0 to 1 percent slopes. They formed in loamy and sandy alluvium.
Mean Annual Precipitation: 26 to 40 inches.
Mean Annual Temperature: 58 to 64 degrees F.
Thornthwaite Annual P-E indices: 44 to 64.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Asher soils and Amber, Dale, Gaddy, Lela, McLain, Port, and Yahola soils. Asher, Dale, Lela, and McLain soils occur on similar areas but are slightly concave while Keokuk soils are slightly convex. Amber soils are on side slopes and lack a mollic epipedon. Dale soils have a mollic epipedon more than 20 inches thick and have a fine-silty control section. Gaddy, Port, and Yahola soils are usually on lower flood plains that are closer to the stream channel. In addition, Gaddy soils have a sandy control section. Lela and McLain soils have a fine control section. Port soils have a mollic epipedon more than 20 inches thick and have a fine-silty control section. Yahola soils have a coarse-loamy control section.

DRAINAGE AND PERMEABILITY: Well drained; runoff is slow; permeability is moderate.

USE AND VEGETATION: Mainly cultivated to alfalfa, wheat, grain sorghums, peanuts, and soybeans. A lesser acreage is used for tame pasture or rangeland. Native vegetation is mainly tall grasses with scattered bottomland hardwood trees.

DISTRIBUTION AND EXTENT: Central Rolling Red Prairies of Oklahoma. The soil is of moderate extent.

MLRA OFFICE RESPONSIBLE: Temple, Texas

SERIES ESTABLISHED: Pottawatomie County, Oklahoma; 1974.

REMARKS: These soils were formerly included in the Dale series. Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from the surface of the soil to a depth of 12 inches (A horizon).
Cambic horizon - the zone from 12 inches to a depth of 24 inches (Bw horizon).
Fluventic - and irregular decrease in organic carbon content from a depth of 25cm to a depth of 125 cm.

ADDITIONAL DATA: Laboratory data on organic matter dated 6/20/73 by O.S.U. from the series location.