LOCATION ELKHART IL
The Elkhart series consists of very deep, well drained, moderately permeable soils on uplands and high stream terraces. Slope ranges from 0 to 18 percent. These soils formed in calcareous loess. Mean annual precipitation is about 889 mm (35 inches), and mean annual temperature is about 11.1 degrees C (52 degrees F).
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 174 meters (570 feet) above mean sea level. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 20 cm (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. [15 to 25 cm (6 to 10 inches) thick]
A--20 to 25 cm (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 15 cm (0 to 6 inches) thick]
BA--25 to 38 cm (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 15 cm (0 to 6 inches) thick]
Bt1--38 to 56 cm (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--56 to 71 cm (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 20 to 76 cm (8 to 30 inches).]
BCt--71 to 79 cm (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 13 cm (0 to 5 inches) thick]
C--79 to 152 cm (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 oxidized iron 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:
Thickness of the mollic epipedon: typically 25 to 51 cm (10 to 20 inches), but is as thin as 18 cm (7 inches) in pedons that are 20 inches to the base of the argillic horizon.
Depth to the base of the argillic horizon: 51 to 102 cm (20 to 40 inches)
Depth to carbonates: 51 to 102 cm (20 to 40 inches)
Average content of clay in the particle-size control section: between 25 and 35 percent
Average content of sand throughout the series control section: less than 8 percent
Ap, A, and/or AB horizons:
Value: 2 or 3
Chroma: 1 to 3
Texture: typically silt loam, but some eroded or severely eroded pedons are silty clay loam.
Reaction: moderately acid to slightly alkaline
BA and Bt horizons:
Hue: 10YR or 7.5YR
Value: 3 to 5
Chroma: 3 to 6
Texture: dominantly silty clay loam, but some subhorizons are silt loam.
Reaction: moderately acid to neutral
BC and/or BCk horizons:
Hue: 7.5YR, 10YR or 2.5Y
Value: 4 to 6
Chroma: 3 to 6
Texture: silt loam or silty clay loam
Average content of clay: less than 30 percent
Reaction: slightly acid to moderately alkaline
BCk horizon (where it occurs) 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.
Hue: 10YR, 2.5Y or 5Y
Value: 4 to 6
Chroma: 1 to 6
Texture: silt or silt loam
Clay content: 20 to 27 percent
Reaction: slightly alkaline or moderately alkaline
COMPETING SERIES: These are the
Waupecan series. Ashdale and Ripon soils have limestone bedrock within a depth of 152 cm (5 feet). Broadwell, Dinsdale, Meadowbank, Mendota, Mickle, 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, and Wakenda soils do not have carbonates within a depth of 102 cm (40 inches). Elmont soils have a paralithic contact at depths of 102 to 152 cm (40 to 60 inches) in weathered shale. Gymer soils formed in silty alluvial of
Loveland age. Sibley soils have mollic epipedons thicker than 61 cm (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 10.0 to 12.2 degrees C (50 to 54 degrees F), and mean annual precipitation ranges from 762 to 1016 mm (30 to 40 inches). Frost free period range from 160 to 180 days and elevation ranges from 152 to 305 meters (500 to 1000 feet) above mean sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing
Osco soils and the
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 SATURATED HYDRAULIC CONDUCTIVITY: Well drained. These soils have an apparent seasonal high water table at a depth of 122 TO 183 CM (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. Saturated hydraulic conductivity is moderately high to high (4.23 to 14.11 micrometers per second). 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: MLRAs 108A, 108B, and 115C in Illinois. The soils of this series are moderately extensive (nearly 60,000 acres correlated).
MLRA SOIL SURVEY REGIONAL OFFICE (MO) 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 38 cm (15 inches) (Ap, A, and BA horizons); argillic horizon - the zone from about 38 to 79 cm (15 to 31 inches) (Bt1, Bt2, and BCt horizons).
National Cooperative Soil Survey