LOCATION SPILLCO IA+MNEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Cumulic Hapludolls
TYPICAL PEDON: Spillco loam with a slope of about 1 percent - cultivated. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 8 inches; black (10YR 2/1) loam, very dark gray (10YR 3/1) dry; weak fine granular structure; friable; neutral; clear smooth boundary.
A1--8 to 13 inches; black (10YR 2/1) loam, very dark gray (10YR 3/1) dry; weak fine subangular blocky and granular structure; friable; common worm castings; neutral; gradual smooth boundary.
A2--13 to 23 inches; black (10YR 2/1) loam, very dark gray (10YR 3/1) dry; weak medium subangular blocky structure parting to weak fine subangular blocky and granular; friable; common worm castings; neutral; gradual smooth boundary.
A3--23 to 28 inches; very dark gray (10YR 3/1) loam, dark gray (10YR 4/1) dry; weak medium subangular blocky structure parting to weak fine subangular blocky; friable; few worm castings; strong effervescence; slightly alkaline; gradual smooth boundary.
A4--28 to 38 inches; very dark gray (10YR 3/1) loam, dark gray (10YR 4/1) dry; weak medium subangular blocky structure parting to weak fine subangular blocky; friable; few worm castings; few small snail shells; strong effervescence; moderately alkaline; gradual smooth boundary. (Combined thickness of the A horizons is 30 to 48 inches.)
AC--38 to 50 inches; very dark gray (10YR 3/1) loam; weak medium prismatic and subangular blocky structure; friable; strong effervescence; moderately alkaline; gradual smooth boundary. (0 to 12 inches thick)
C--50 to 60 inches; very dark grayish brown (10YR 3/2) loam; massive with vertical parting; friable; strong effervescence; moderately alkaline.
TYPE LOCATION: Lyon County, Iowa; near the south edge of Rock Rapids; 550 feet south and 60 feet west of the northeast corner of sec. 9, T. 99 N., R. 45 W.
RANGE IN CHARACTERISTICS: Solum thickness typically is 36 to 50 inches but ranges from 30 to 60 inches. The depth to free carbonates is typically 18 to 24 inches and ranges from 12 to 36 inches. The soil is neutral or mildly alkaline above the calcareous part of the solum and mildly alkaline or moderately alkaline in the calcareous part. The A horizon is black (10YR 2/1) or very dark brown (10YR 2/2) in the upper part and ranges from black (10YR 2/1) to very dark grayish brown (10YR 3/2) in the lower part. Some pedons have an A horizon with hues of 2.5Y in the lower part. The A horizon is usually loam, but is silt loam with about 25 to 45 percent sand in some pedons. Snail shells are commonly present in some part of the A horizon. Mottles are lacking above a depth of 36 inches. Mottles of high and low chroma are present in some pedons below a depth of 36 inches. Colors with value of 3 or less and chroma of 2 or less extend to depths of 40 inches or more. Average clay content of the 10- to 40-inch control section is about 18 to 26 percent, and the sand content typically is 30 to 40 percent with extreme ranges of 25 to 45 percent. The C horizon is loam, sandy loam, clay loam or less commonly silty clay loam or silt loam.
COMPETING SERIES: These are the Alsea, DuPage, Olmitz, Ross, Spillville, Terril, and Turlin in the same family and the Bon and Davis series. Alsea soils are more acid, have annual precipitation in excess of 60 inches and a 200 day dry growing season. DuPage soils are calcareous throughout the profile. Olmitz, Spillville, Terril and Turlin soils are leached of carbonates to depths greater than 40 inches. Ross soils have colors with value of 3 or less extending to shallower depths, lack moderately alkaline horizons and lack horizons with strong effervescence. Bon soils are calcareous throughout. Davis soils are leached of carbonates to depths of 30 to 50 inches or more and have a regular decrease in content of organic carbon with depth.
GEOGRAPHIC SETTING: Spillco soils are on bottom lands. In places these soils are in the lower part of upland drainageways. Slope gradients are typically less than 2 percent. Spillco soils formed in dark-colored alluvium that contains between 25 and 45 percent sand. Mean annual temperature is about 45 to 49 degrees F, and mean annual precipitation ranges from 24 to 28 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Colo, Calco, and Kennebec soils and the competing Davis, Spillville, and Terril soils. Colo and Calco soils contain more clay and less sand. Kennebec soils contain more silt and less sand and lack carbonates in the solum. These soils are on similar landscape positions.
DRAINAGE AND PERMEABILITY: Moderately well or somewhat poorly drained. Runoff is slow. Permeability is moderate.
USE AND VEGETATION: Some areas are cropped to corn and soybeans. Areas that have a high frequency of flooding are used for pasture. Native vegetation was tall prairie grasses and associated plants.
DISTRIBUTION AND EXTENT: Northwestern Iowa and southwestern Minnesota. Spillco soils are inextensive.
MLRA OFFICE RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Lyon County, Iowa, 1973.
REMARKS: The textural ranges overlap with the Davis series. In Lyon County, Iowa, Spillco soils were mapped on landscape positions that are more subject to flooding than the positions on which Davis was mapped.