LOCATION ALLISON IL+INEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Cumulic Hapludolls
TYPICAL PEDON: Allison silty clay loam on a northwest-facing concave slope of one percent in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 8 inches; very dark grayish brown (10YR 3/2) silty clay loam, dark grayish brown (10YR 4/2) dry; weak fine and medium granular structure; firm; many fine roots; neutral; abrupt smooth boundary.
A3--8 to 17 inches; very dark grayish brown (10YR 3/2) silty clay loam, dark grayish brown (10YR 4/2) dry; weak fine subangular blocky structure; firm; many fine roots; continuous very dark gray (10YR 3/l) coatings on faces of peds; neutral; diffuse smooth boundary. (Combined thickness of the A horizon is 10 to 20 inches.)
B21--17 to 35 inches; dark brown (10YR 3/3) silty clay loam, brown (10YR 5/3) dry; weak medium and coarse subangular blocky structure; firm; common fine roots; very dark grayish brown (10YR 3/2) coatings on faces of peds and worm casts; neutral; diffuse smooth boundary.
B22-35 to 50 inches; dark brown (10YR 3/3) silty clay loam, brown (10YR 5/3) dry; weak coarse prismatic structure parting to weak medium subangular blocky; firm; few fine roots; very dark grayish brown (10YR 3/2) coatings on faces of peds; neutral; diffuse smooth boundary.
B23--50 to 60 inches; brown (10YR 4/3) silty clay loam; weak coarse prismatic structure parting to weak medium subangular blocky; firm; thin dark brown (10YR 3/3) coatings on faces of peds; neutral; diffuse smooth boundary. (Combined thickness of the B2 horizon is 20 to 45 inches.)
C--60 to 70 inches; brown (10YR 4/3) silty clay loam; weak coarse prismatic structure; firm; few dark brown (10YR 3/3) coatings on vertical cleavage planes; neutral.
TYPE LOCATION: Gallatin County, Illinois; about 12 miles east of Ridgway; 450 feet east and 550 feet north of the center of sec. 25, T. 8 S., R. 10 E.
RANGE IN CHARACTERISTICS: The thickness of the solum ranges from 30 to greater than 60 inches. The mollic epipedon typically is greater than 36 inches in thickness and ranges from 24 to 60 inches. The control section averages between 27 and 35 percent clay. These soils are slightly acid to mildly alkaline throughout. Free carbonates are lacking above depths of 40 inches.
The A horizon has hue of 10YR, value of 2 or 3 moist and 4 or 5 dry, and chroma of 1 through 3. The A horizon is dominantly silty clay loam but includes silt loam in some pedons.
The B2 horizon commonly has hue of 10YR, value of 2 through 4, and chroma of 2 through 4. Some pedons have hue of 7.5YR. Some pedons contain mottles below the mollic epipedon or in the lower part of the B horizon. They have hue of 10YR or 7.5YR, value of 4 through 6, and chroma of 2 through 4. The B horizon typically is silty clay loam and in many pedons contains strata of silt loam, loam, clay loam, or sandy loam below depths of 30 inches. Some pedons have a B3 horizon. It has properties in the same range as the B2 horizon.
The C horizon has hue of 10YR of 7.5YR, value 4 through 6, and chroma of 3 through 6. It commonly is silty clay loam with thin strata with textures that range from fine sand to silt loam. The C horizon is slightly acid to mildly alkaline.
COMPETING SERIES: These are the Ely, Huntsville, Ivan, Judson, Kahola, Kennebec, Lawson, Lindstrom, Littleton, Napier, Sturkie, and Worthen series in the same family and the Otter, Raddle, and Radford soils. Ely, Lawson, Littleton, and Radford soils have lower chroma in the lower part of the control section in conjunction with value of 4 or more, or mottles or other evidence of wetness. Huntsville, Lindstrom, Napier, and Worthen soils contain less than 27 percent clay in the control section. Ivan soils are calcareous throughout. Judson soils have more strongly developed structure and lack strata or lenses of coarser textured material in the lower part of the B horizon. Kahola soils are calcareous in the lower part of the mollic epipedon and within the control section. Kennebec soils lack a B horizon and have chroma of 1 or 2 to depths of 5 feet or more. Sturkie soils contain more sand in the upper part of the control section. Otter soils lack a B horizon and have grayer colors throughout. Raddle soils have mollic epipedons less than 24 inches thick.
GEOGRAPHIC SETTING: Allison soils are on slightly elevated parts of flood plains. Slopes range from 0 to 7 percent. These soils formed in stratified moderately fine and medium textured alluvium. Mean annual temperature varies from 51 to 57 degrees F, and mean annual precipitation varies from 35 to 45 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Beaucoup, Comfrey, Emma, Karnak, Tice, and Sawmill soils. The poorly drained Beaucoup, Comfrey, Karnak, and Sawmill soils have grayer colors throughout and are lower on the flood plains. In addition, Karnak soils contain more clay in the control section and Comfrey soils contain more sand in the control section. The somewhat poorly drained Tice soils are on slightly lower parts of the flood plain and have mottles within 16 inches of the soil surface or gray colors within 6 inches below the mollic epipedon and have a mollic epipedon less than 24 inches thick. Emma soils are on similar nearby landscapes, lack mollic epipedons and have more acid reaction throughout the solum.
DRAINAGE AND PERMEABILITY: Well drained and moderately well drained. Runoff is slow or medium. Permeability is moderate.
USE AND VEGETATION: Most areas of Allison soils are cultivated. Corn and soybeans are the principal row crops. Small areas are in woodland. Native vegetation was mixed hardwoods and grasses.
DISTRIBUTION AND EXTENT: Illinois and Indiana. The extent is moderate.
MLRA OFFICE RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Lawrence County, Illinois, 1952.
REMARKS: All the published typical pedons have silty clay loam texture in the A horizon. The data from the type location is just over the line into silty clay but the difference is within the range of normal error.