LOCATION OKABENA MNEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Aquic Hapludolls
TYPICAL PEDON: Okabena silty clay loam with a slightly convex slope of about 1 percent on a moraine in a cultivated field. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 10 inches; black (10YR 2/1) silty clay loam, very dark gray (10YR 3/1) dry; moderate fine subangular blocky structure; friable; slightly acid; abrupt smooth boundary. (Combined thickness of Ap and A horizons is 9 to 18 inches).
AB--10 to 15 inches; black (10YR 2/1) silty clay loam, very dark gray (10YR 3/1) dry; weak fine and very fine subangular blocky structure; friable; slightly acid; few dark brown (10YR 3/3) streaks on faces of peds; gradual wavy boundary. (0 to 6 inches thick).
Bw--15 to 22 inches; olive brown (2.5Y 4/3) silty clay loam; weak fine subangular blocky structure; friable; slightly acid; few dark yellowish brown (10YR 4/4) streaks on faces of peds; gradual wavy boundary.
Bk--22 to 43 inches; grayish brown (2.5Y 5/2) silt loam; weak fine subangular blocky structure; friable; common white (10YR 8/1) masses of carbonates; common fine distinct yellowish brown (10YR 5/6) Fe concentrations; strongly effervescent; moderately alkaline; clear wavy boundary. (6 to 20 inches thick.)
Cg1--43 to 48 inches; grayish brown (2.5Y 5/2) silt loam; massive; few thin seams of very fine sandy loam on faces of peds; few white (10YR 8/1) masses of carbonates; friable; common medium prominent strong brown (7.5YR 5/6) Fe concentrations; strongly effervescent; slightly alkaline; gradual wavy boundary.
2Cg2--48 to 80 inches; olive gray (5Y 5/2) loam; massive; friable; about 6 percent gravel; few white (10YR 8/1) masses of carbonates; common fine yellowish brown (10YR 5/6) Fe concentrations; slightly effervescent; slightly alkaline.
TYPE LOCATION: Nobles County, Minnesota; about 2.5 miles northwest of Worthington; 2100 feet south and 40 feet east of northwest corner of sec. 9, T. 102 N., R. 39 W. USGS Worthington North quadrangle; lat. 43 degrees 39 minutes 13 seconds N., long. 95 degrees 31 minutes 56 seconds W., NAD27.
RANGE IN CHARACTERISTICS: Depth to free carbonates range from 20 to 40 inches. Depth to glacial till ranges from 40 to 60 inches. The silty mantle contain less than 3 percent rock fragments by volume and the till contains 2 to 8 percent rock fragments. The mollic epipedon ranges from 9 to 18 inches in thickness. The 10 to 40 inch control section averages between 20 to 35 percent clay and typically 2 to 10 percent fine sand and coarser but ranges to as much as 15 percent.
The A horizon has 10YR hue, value of 2 or 3, and chroma of 1 or 2. It typically is silty clay loam, but silt loam and loam high in content of very fine sand are included in the range. It is moderately acid through neutral.
The Bw horizon has 10YR or 2.5Y hue, value of 3 to 5 and chroma of 2 to 4.It is silty clay loam or silt loam. In some pedons it is stratified with these textures as well as having thin coarser textured strata. It is moderately acid through neutral.
Some pedons have a BC horizon that is slightly alkaline.
The Bkg horizon has 2.5Y or 5Y hue, value of 5 or 6, and chroma of 1 or 2. It is silty clay loam or silt loam. It is slightly alkaline or moderately alkaline.
The Cg horizon has 2.5Y or 5Y hue, value of 5 or 6, and chroma of 1 or 2. It is silt loam or silty clay loam. In some pedons it is stratified with these textures as well as having thinned coarser textured strata. It is slightly alkaline or moderately alkaline.
The 2Cg horizon has 2.5Y or 5Y hue, value of 5 or 6, and chroma of 1 or 2. It typically is loam, but clay loam is included in the range. The moist bulk density ranges from 1.35 to 1.6 g/cc. It is slightly alkaline or moderately alkaline.
COMPETING SERIES: These are the Amana, Breeds, Grantcenter Joy, Joyce, Kingston, Klingmore, Klinger, Lakefield, Larpenteur, Minden, Muscatine, Nerwoods, Primghar, and Ransom series in the same family. Amana soils have thicker sola, lack free carbonates within depths of 60 inches, and have coatings of clean silt and sand particles on faces of peds in the Bw and BC horizons. Breeds soils have shale paralithic contact. Grantcenter soils average less than 22 percent clay in underlying parent material. Joy, Klinger, Minden, and Muscatine soils have thicker sola. Kingston soils have less sand in the series control section. Klingmore soils lack free carbonates within depths of 40 inches. Lakefield and Larpentuer soils have free carbonates within 10 inches. Nerwoods soils have dense glacial till within 60 inches. Primghar soils formed in loess and have more clay in the A horizon and the upper part of the B horizon. Ransom soils have loam or clay loam 2B or 2C horizons at depths of less than 40 inches.
GEOGRAPHIC SETTING: These soils have plane or slightly convex slopes on glacial lake plains or moraines. Slope gradients range from 0 to 3 percent. These soils formed 40 to 60 inches of silty lacustrine sediments or loess overlying glacial till of Late Wisconsinan Age. Mean annual air temperature is approximately 45 to 52 degrees F, and mean annual precipitation is approximately 26 to 30 inches. Elevation above sea level is 1100 to 1300 feet. Frost free days range from 145 to 160.
GEOGRAPHICALLY ASSOCIATED SOILS: The main ones are the Clarion, Nicollet, Kingston, Madelia and Webster soils. The moderately well drained Clarion soils are on gently undulating slopes. The somewhat poorly drained Kingston and Nicollet soils occupy similar slopes. are on nearly level slopes. The poorly drained Madelia and Webster soils are on nearly level slopes.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained. Surface
runoff is low. Permeability is moderate. Depth to a seasonal high saturation is at 1.5 to 2.0 feet at sometime during November to May in normal years.
USE AND VEGETATION: Almost all of this soil is cropped to corn and soybeans. Native vegetation is tall grass prairie.
DISTRIBUTION AND EXTENT: Southern Minnesota. Not extensive.
MLRA OFFICE RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Nobles County, Minnesota, 2004.
REMARKS: Diagnostic horizon and features recognized in this pedon are: mollic epipedon - the zone from the surface of the soil to a depth of 15 inches (Ap, AB horizons); Cambic horizon - zone from 15 to 22 inches (Bw horizon); Calcic horizon - zone from - 22 to 43 inches (Bk horizon).