LOCATION ELKHART ILEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Typic Argiudolls
TYPICAL PEDON: Elkhart silt loam - on a southwest-facing slope of 6 percent in a cultivated field at an elevation of 570 feet. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 8 inches; very dark grayish brown (10YR 3/2) silt loam, dark grayish brown (10YR 4/2) dry; weak fine and medium granular structure; friable; common very fine roots; slightly acid; abrupt smooth boundary. (6 to 10 inches thick)
A--8 to 10 inches; very dark grayish brown (10YR 3/2) silt loam, dark grayish brown (10YR 4/2) dry; moderate fine granular structure; friable; common very fine roots; slightly acid; clear smooth boundary. (0 to 6 inches thick)
BA--10 to 15 inches; dark brown (10YR 3/3) silty clay loam, brown (10YR 4/3) dry; moderate very fine and fine subangular blocky structure; friable; common very fine roots; common faint very dark grayish brown (10YR 3/2) organic coatings on faces of peds; slightly acid; clear smooth boundary. (0 to 6 inches thick)
Bt1--15 to 22 inches; dark yellowish brown (10YR 4/4) silty clay loam; moderate fine subangular blocky structure; firm; few very fine roots; common distinct very dark grayish brown (10YR 3/2) organo-clay films on faces of peds; slightly acid; clear smooth boundary.
Bt2--22 to 28 inches; dark yellowish brown (10YR 4/4) silty clay loam; moderate fine and medium subangular blocky structure; firm; few very fine roots; few distinct dark brown (10YR 3/3) organo-clay films on faces of peds; slightly acid; clear smooth boundary. (Combined thickness of the Bt horizons is 8 to 30 inches.)
BCt--28 to 31 inches; yellowish brown (10YR 5/4) silty clay loam; weak medium and coarse subangular blocky structure; friable; few very fine roots; few faint brown (10YR 4/3) clay films on faces of peds; few fine black (5YR 2.5/1) very weakly cemented manganese oxide concretions with diffuse boundaries in ped interiors; neutral; clear smooth boundary. (0 to 5 inches thick)
C--31 to 60 inches; yellowish brown (10YR 5/4) silt loam; massive; friable; few very fine roots in the upper 10 inches; common fine prominent strong brown (7.5YR 5/8) masses of iron accumulation in ped interiors; common medium distinct gray (10YR 6/1) iron depletions along root channels and pores; strongly effervescent; moderately alkaline.
TYPE LOCATION: Logan County, Illinois; about 1/2 mile south of Broadwell; 2,060 feet south and 1,248 feet west of the northeast corner of sec. 32, T. 19 N., R. 3 W.; USGS Broadwell topographic quadrangle; lat. 40 degrees 03 minutes 26 seconds N. and long. 89 degrees 26 minutes 58 seconds W.; NAD 27.
RANGE IN CHARACTERISTICS: The depth to the base of the argillic horizon ranges from 20 to 40 inches. The depth to carbonates is 20 to 40 inches. The mollic epipedon typically is 10 to 20 inches in thickness, but is as thin as 7 inches in pedons that are 20 inches to the base of the argillic horizon. The particle-size control section averages between 25 and 35 percent clay. Sand content averages less than 8 percent throughout the series control section.
The Ap, A, or AB horizon has hue of 10YR, value of 2 or 3, and chroma of 1 to 3. It typically is silt loam, but some eroded or severely eroded pedons are silty clay loam. Reaction ranges from moderately acid to slightly alkaline.
The BA, Bt, BC, or BCk horizon has properties as follows:
The BA and Bt horizons have hue of 10YR or 7.5YR, value of 3 to 5, and chroma of 3 to 6. Texture dominantly is silty clay loam, but some subhorizons are silt loam. Reaction ranges from moderately acid to neutral.
The BC horizon has hue of 7.5YR, 10YR, or 2.5Y; value of 4 to 6; and chroma of 3 to 6. It is silt loam or silty clay loam and averages less than 30 percent clay. Reaction is slightly acid to moderately alkaline.
Some pedons contain a BCk horizon with textures and colors similar to the BC horizon. The BCk horizon shows evidence of carbonate translocation from upper horizons. Evidence includes carbonate concretions, nodules, accumulations, and coatings of secondary carbonates. These horizons are transitional to the C horizon parent material below.
The C horizon has hue of 10YR, 2.5Y, or 5Y; value of 4 to 6; and chroma of 1 to 6. It is silt or silt loam. Clay content ranges from 20 to 27 percent. Reaction is slightly alkaline or moderately alkaline.
COMPETING SERIES: These are the Ashdale, Broadwell, Dinsdale, Douglas, Elmont, Healing, Lycurgus, Malcolm, Meadowbank, Mendota, Mickle(T), Ogle, Osco, Parkway, Plano, Proctor, Richwood, Ripon, Sibley, Sidell, Tama, Tecumseh, Toddville, Wakenda, Waupecan, and Wiota series. Ashdale and Ripon soils have limestone bedrock within a depth of 5 feet. Broadwell, Dinsdale, Meadowbank, Mendota, Mickle(T), Ogle, Parkway, Plano, Proctor, Richwood, Sidell, Tecumseh, Toddville and Waupecan soils have more than 8 percent sand in the lower part of the series control section. Douglas, Healing, Lycurgus, Malcolm, Osco, Tama, Wakenda, and Wiota soils do not have carbonates within a depth of 40 inches. Elmont soils have a paralithic contact at depths of 40 to 60 inches in weathered shale. Sibley soils have mollic epipedons thicker than 24 inches.
GEOGRAPHIC SETTING: Elkhart soils are on uplands and on high stream terraces. Slope ranges from 0 to 18 percent. These soils formed in calcareous loess. Mean annual temperature ranges from 50 to 54 degrees F., and mean annual precipitation ranges from 30 to 40 inches. Frost free period range from 160 to 180 days and elevation ranges from 500 to 1000 feet above sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Osco soils and the Buckhart, Harco, Sylvan, and Tallula soils. Osco soils are in similar positions on the landscape nearby, and commonly are upslope where the loess is leached more deeply. The Buckhart soils are in similar positions on the landscape, have a shallower seasonal high watertable and are leached more deeply. The somewhat poorly drained Harco soils are in less sloping positions on the landscape and form a drainage sequence with Elkhart soils. Sylvan soils are in similar positions on the landscape and do not have a mollic epipedon. They form a bio-sequence with Elkhart soils. Tallula soils are typically in positions downslope from Elkhart soils. They contain less clay in the subsoil and do not have an argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained. These soils have an apparent seasonal high water table at a depth of 4 to 6 feet at some time between February and April in most years. The potential for surface water runoff is low on the lesser slopes and medium on the steeper slopes. Permeability is moderate.
USE AND VEGETATION: Most areas of Elkhart soils are cultivated. Corn, soybeans, small grain, and meadow are the principal crops. Some areas are used for pasture. Native vegetation is prairie grasses.
DISTRIBUTION AND EXTENT: Illinois. The soils of this series are moderately extensive (nearly 60,000 acres correlated) in MLRAs 108 and 115.
MLRA OFFICE RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Rock Island County, Illinois, 1972.
REMARKS: Based upon detailed review of drainage properties, landscapes, soil descriptions, and other data, the series is reclassified to its previous classification of Typic Argiudolls, rather than Oxyaquic Argiudolls.
Diagnostic horizons and features observed in this pedon are: mollic epipedon - the zone from the surface of the soil to a depth of 15 inches (Ap, A, and BA horizons); argillic horizon - the zone from about 15 to 31 inches (Bt1, Bt2, and BCt horizons).