LOCATION MCPAUL IA+MN MO NE SDEstablished Series
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, calcareous, mesic Mollic Udifluvents
TYPICAL PEDON: McPaul silt loam - nearly level flood plain - cultivated. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 7 inches; very dark grayish brown (10YR 3/2) light silt loam and a few dark grayish brown (10YR 4/2) and brown (10YR 4/3) peds; grayish brown (10YR 5/2) dry; very weak fine granular structure; very friable; slight effervescence; neutral; abrupt smooth boundary. (6 to 10 inches thick)
C--7 to 60 inches; alternating layers of grayish brown (10YR 5/2) dark grayish brown (10YR 4/2), and brown (l0YR 5/3) silt loam (15 percent clay); pale brown (10YR 6/3) dry, few very thin darker horizontal strata; common fine faint yellowish brown (10YR 5/8) and strong brown (7.5YR 5/6 and 5/8) mottles in 40 to 48 inch zone; massive but parts along horizontal planes of weakness; very friable; slight effervescence; slightly alkaline.
TYPE LOCATION: Fremont County, Iowa; about 4 miles W-SW of Sidney; 1,500 feet west and 860 feet north of the southeast corner of sec. 36, T. 69 N., R. 43 W; about 100 feet south of large round grain bin and 30 feet west of farm lane at elevation 925 feet above mean sea level. U.S.G.S. Sidney, Iowa Topographic Quadrangle; latitude 40 degrees, 43 minutes, and 53 seconds N., longitude 95 degrees, 44 minutes, and 00 seconds W.
RANGE IN CHARACTERISTICS: The solum thickness is less than 10 inches and is the same as the thickness of the ochric epipedon. McPaul soils contain free carbonates throughout, and are slightly alkaline or moderately alkaline. These soils formed in sediments which have evident stratification and have changed little since deposition.
The series control section averages between 10 and 18 percent clay and 5 to 15 percent sand, most of which is very fine sand. Individual darker colored strata below 24 inches are silt loam containing more than 18 percent clay or silty clay loam containing less than 30 percent clay. In some pedons buried layers with more than 5 percent organic matter below a depth of 40 inches contain more than 30 percent clay.
The A or Ap horizon has hue of 10YR, value of 3 or 4, and chroma of 2 or 3. It is silt loam.
The C horizon has hue of 10YR, value of 4 or 5, and chroma of 2 or 3. Pedons that have thin strata of very dark grayish brown (10YR 3/2) in the C horizon are within the range of the series. Common faint yellowish brown, brown, and strong brown, or a few gray mottles or stains are in the lower part of the C horizon. These mottles and stains are mainly on the faces of the stratification planes.
COMPETING SERIES: These are the Haynie, and Ion series. Haynie soils include 2.5Y hue in the matrix and contain more than 15 percent sand in the series control section. Ion soils have dark colored layers within the buried soil in the lower 2/3 of the series control section.
GEOGRAPHIC SETTING: Most McPaul soils are in settling basins and near drainage channels on narrow flood plains of tributary streams that flow across the slack water areas of flood plains of large rivers. Slopes typically are less than 2 percent but range to 5 percent. McPaul soils formed in 3 to 8 feet of calcareous, stratified alluvium washed from soils formed in loess on adjoining uplands. Mean annual air temperature ranges from about 47 to 56 degrees F, and mean annual precipitation from about 26 to 32 inches. Frost free days range from 150 to 180. Elevation ranges from 900 to 1200 feet above mean sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Moville and Rawles soils and the Castana, Colo, Kennebec, Luton, and Napier soils. The darker colored Castana and Napier soils are on adjacent foot slopes. The Moville soils and the darker colored, more clayey Colo, Kennebec, and Luton soils are on lower parts of the flood plains. Rawles soils are on similar landscape positions as the McPaul soils.
DRAINAGE AND PERMEABILITY: Moderately well or somewhat poorly drained. Depth to seasonal high water table is 3 to 5 feet. Runoff is slow. Permeability is moderate. These soils are subject to rare to common flooding for very brief periods in most years.
USE AND VEGETATION: Most areas are under cultivation. Corn and soybeans are the principal crops, but small grain and hay are also grown. Several areas are land-leveled and irrigated. Along narrow tributaries a few areas are used for permanent pasture because they are small or cut up badly by channels.
DISTRIBUTION AND EXTENT: Western Iowa, southeastern Minnesota, eastern Nebraska, Kansas, South Dakota, and Missouri. McPaul soils are of large extent.
MLRA OFFICE RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Mills County, Iowa, 1941.
REMARKS: Diagnostic horizons and features recognized in this pedon are: Ochric epipedon - zone from the surface to a depth of 7 inches (Ap horizon); udic moisture regime.
ADDITIONAL DATA: Laboratory data is available from Iowa State University Soil Survey Laboratory.