LOCATION OSKALOOSA ILInactive Series
TAXONOMIC CLASS: Fine, smectitic, mesic Fragiaquic Hapludalfs
TYPICAL PEDON: Oskaloosa silt loam - on a northwest facing slope of about 3 percent in a cultivated field at an elevation of about 522 feet above MSL. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 8 inches; dark grayish brown (10YR 4/2) silt loam, pale brown (10YR 6/3) dry; moderate very fine and fine granular structure; friable; common fine and medium rounded black (N 2.5/) iron-manganese nodules throughout; neutral; abrupt smooth boundary. (6 to 10 inches thick)
E--8 to 14 inches; brown (10YR 5/3) silt loam, light gray (2.5Y 7/2) dry; weak medium platy structure; friable; common medium distinct yellowish brown (10YR 5/6) masses of iron accumulation in the matrix; common fine and medium rounded black (N 2.5/0) iron-manganese nodules throughout; moderately acid; clear smooth boundary. (3 to 14 inches thick)
Bt1--14 to 19 inches; brown (10YR 5/3) silty clay loam; moderate fine prismatic structure parting to moderate very fine and fine angular blocky; friable; few distinct light gray (10YR 7/2) dry silt coatings and few distinct dark grayish brown (10YR 4/2) clay films on faces of peds; many fine faint light brownish gray (10YR 6/2) iron depletions in the matrix; common fine distinct reddish brown (5YR 4/4) masses of iron and manganese accumulation in the matrix; common fine and medium rounded black (N 2.5/) iron-manganese nodules throughout; very strongly acid; clear smooth boundary.
Bt2--19 to 28 inches; brown (10YR 5/3) silty clay; strong fine and medium prismatic structure parting to strong fine angular blocky; very firm; common prominent dark grayish brown (10YR 4/2) clay films and common distinct light gray (10YR 7/2) dry silt coatings on faces of peds; many fine and medium faint light brownish gray (10YR 6/2) iron depletions in the matrix; common medium faint brown (7.5YR 4/4) masses of iron and manganese accumulation in the matrix; few fine and medium rounded black (N2.5/) iron-manganese nodules throughout; very strongly acid; abrupt smooth boundary.
Bt3--28 to 34 inches; brown (10YR 5/3) silty clay loam; moderate fine and medium prismatic structure parting to moderate fine angular blocky; firm; few prominent dark grayish brown (10YR 4/2) clay films on faces of peds; few distinct light gray (10YR 7/2) dry silt coatings on faces of peds; many medium faint light brownish gray (10YR 6/2) iron depletions in the matrix; common medium faint brown (7.5YR 4/4) masses of iron and manganese accumulation in the matrix; few fine and medium rounded black (N 2.5/) iron-manganese nodules throughout; very strongly acid; clear smooth boundary.
Bt4--34 to 44 inches; brown (10YR 5/3) silty clay loam; moderate medium prismatic structure parting to moderate medium angular blocky; firm; few distinct dark grayish brown (10YR 4/2) clay films on faces of peds; many medium and coarse faint light brownish gray (10YR 6/2) iron depletions in the matrix; common medium faint brown (7.5YR 4/4) masses of iron and manganese accumulation in the matrix; few fine and medium rounded black (N 2.5/) iron-manganese nodules throughout; very strongly acid; clear smooth boundary. (combined thickness of the Bt and Btg horizons is 16 to 32 inches)
2Btx--44 to 66 inches; brown (10YR 5/3) silty clay loam; moderate coarse prismatic structure; very firm; brittle in 60 percent; few distinct dark grayish brown (10YR 4/2) clay films on faces of peds; many prominent light gray (10YR 7/2) silt coatings on faces of peds; many medium and coarse faint light brownish gray (10YR 6/2) iron depletions in the matrix; common coarse distinct yellowish brown (10YR 5/6) masses of iron accumulation and dark yellowish brown (10YR 4/6) masses of iron and manganese accumulation in the matrix; common fine and medium rounded black (N 2.5/) iron-manganese nodules throughout; strongly acid; clear smooth boundary.
2Bx--66 to 80 inches; 60 percent brown (10YR 5/3), 40 percent yellowish brown (10YR 5/4) silty clay loam; moderate very coarse prismatic structure; very firm; slightly brittle in most parts; very few faint dark grayish brown (10YR 4/2) clay films on faces of peds; many prominent light gray (10YR 7/2) silt coatings on faces of peds; many medium and coarse faint light brownish gray (10YR 6/2) iron depletions in the matrix; common medium and coarse distinct yellowish brown (10YR 5/6) masses of iron accumulation and common medium and coarse distinct dark yellowish brown (10YR 4/6) masses of iron and manganese accumulation in the matrix; common fine and medium black (N 2.5/) iron-manganese nodules throughout; moderately acid. (combined thickness of the Btx and Bx horizons is 6 to 60 inches)
TYPE LOCATION: Clay County, Illinois; located about 1,485 feet south and 1,070 feet east of the northwest corner of sec. 18, T. 2 N., R. 6 E; USGS Johnsonville, Illinois topographic quadrangle; lat. 38 degrees 37 minutes 3.9 seconds N. and long. 88 degrees 34 minutes 49.6 seconds W.; UTM Zone 16S 0362405 easting and 4275338 northing; NAD 27.
RANGE IN CHARACTERISTICS: The depth to layers with greater than 30 percent fragic properties is 40 to 60 inches.The depth to material with greater than 7 percent fine sand or coarser is 30 to 55 inches. The particle size control section averages between 35 and 42 percent clay.
The Ap or A horizon has value of 3 to 5 (6 or 7 dry), and chroma of 1 to 3. Texture is silt loam. It is very strongly acid or strongly acid but ranges to neutral in pedons that have been limed.
The E horizon has value of 4 to 6, and chroma of 2 to 4. Texture is silt loam. Reaction ranges from very strongly acid to neutral.
Some pedons have a BE horizon.
The Bt horizon has hue of 10YR or 2.5Y, value of 4 to 6, and chroma of 2 to 6. Silt coatings on the faces of peds are dominantly in the upper part of the Bt horizon and range from gray to white. It is silty clay loam or silty clay. Reaction ranges from very strongly acid to slightly acid.
The 2Btx, 2Btgx, 2Bx and/or 2Bgx horizon(s) has hue of 10YR, 2.5Y, or 7.5YR, value of 4 to 6, and chroma of 2 to 8. Sand content ranges from 15 to 30 percent. Texture is silt loam, loam, silty clay loam, or clay loam. Reaction is very strongly acid to moderately acid. It is firm, very firm, or extremely firm. It is slightly brittle or brittle in 30 to 60 percent of the volume of one or more subhorizons if the upper boundary of the horizon is above 40 inches or it is brittle in 60 percent or more of the volume in one or more subhorizons if the upper boundary of the horizon is below 40 inches. Prisms, polygons, or other structural units commonly have horizontal dimensions of less than 4 inches in diameter in the upper part, but very coarse structure below a depth of 40 inches is typical.
The 2BC, or 2BCg, where present within 80 inches, have hue of 10YR or 2.5Y, value of 4 to 6, and chroma of 1 to 6. Reaction is very strongly acid to moderately acid. It is silty clay loam, silt loam or loam. Content of rock fragments ranges from 0 to 15 percent by volume.
The 3Agb or 3Btgb horizon, where present within 80 inches, has hue of 7.5YR, 10YR, 2.5Y, or 5Y; value of 4 to 6; chroma of 1 or 2. It is silty clay loam, clay loam, silt loam, or loam. Sand content ranges from 15 to 40 percent. Reaction ranges from moderately acid to neutral. Content of rock fragments ranges from 0 to 15 percent by volume.
COMPETING SERIES: The Cotton series is the only competing series in this family. Cotton soils contain more than 15 percent rock fragments by volume in the lower part of the series control section and are underlain by limestone residuum.
GEOGRAPHIC SETTING: Oskaloosa soils are on shoulders and backslopes of hillslopes and knolls. Slopes range from 1 to 7 percent. Oskaloosa soils formed in 30 to 55 inches of loess and the silty or loamy deposits (pedisediment) thought to be of early Wisconsin age. Some pedons are underlain, within 80 inches, by a Sangamon age paleosol developed in Illinoisan age diamicton. The mean annual air temperature ranges from 54 to 57 degrees F. The mean annual precipitation ranges from 38 to 48 inches. The frost-free days range from 180 to 200 days. Elevation ranges from 350 to 700 feet above mean sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ava, Bluford, Hickory, Hoyleton, Parke, and Wynoose soils. The moderately well drained Ava soils, somewhat poorly drained Bluford soils and the poorly drained Wynoose soils are in a drainage sequence with Oskaloosa soils. Ava soils are on nearby side slopes and convex crests. The Bluford soils have lower chroma matrix colors in the upper part of the series control section and are on nearly level areas and toeslopes adjacent to Oskaloosa soils. Wynoose soils are on broad nearly level parts of the till plain. The well-drained Hickory soils are fine-loamy and are on side slopes below Oskaloosa soils. The somewhat poorly drained Hoyleton soils are mollic intergrades and are on similar nearby ridges. The well drained Parke soils are on higher convex ridges nearby.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained. The potential for surface runoff is medium to high. Permeability is moderately slow or slow. An apparent water table is 1.0 to 2 feet below the surface in January through May in normal years.
USE AND VEGETATION: Most areas of Oskaloosa soils are cultivated. Soybeans, corn, and wheat are the principal crops. Native vegetation is deciduous forest consisting mainly of oak and hickory species.
DISTRIBUTION AND EXTENT: Oskaloosa soils are on the Illinoian ground moraine in southern Illinois. The series is moderately extensive in MLRA 114 and 113.
MLRA OFFICE RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Clay County, Illinois, 2003. The name is a township name in Clay County.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to a depth of 14 inches (Ap and E horizons);
argillic horizon - the zone from 14 to 66 inches ( the Bt and 2Btx horizons);
fragic properties - the zone from 44 to 80 inches (2Btx and 2Bx horizons)
The Oskaloosa series is established to replace Bluford soils in gently sloping and moderately sloping areas where the water table is slightly lower in the profile and the soils do not classify as Aqualfs. Oskaloosa series also recognizes the "fragic" properties that are common in these soils.
ADDITIONAL DATA: University of Illinois and NSSL data is available on supporting pedons at the NRCS state office.