LOCATION RAWLES IA+MNEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, calcareous, mesic Oxyaquic Udifluvents
TYPICAL PEDON: Rawles silt loam, on a nearly level slope, on a flood plain, in a cultivated field, at an elevation of 1,000 feet above sea level. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 8 inches; very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) dry; very weak fine granular structure; very friable; slightly effervescent; slightly alkaline; clear smooth boundary. (5 to 9 inches thick)
C--8 to 26 inches; stratified very dark grayish brown (10YR 3/2) and dark grayish brown (10YR 4/2) silt loam; massive, with weak, thin alluvial stratification; very friable; few fine faint yellowish brown (10YR 5/4) redoximorphic concentrations; slightly effervescent; moderately alkaline; abrupt smooth boundary. (15 to 31 inches thick)
Ab1--26 to 35 inches; black (10YR 2/1) silt loam; weak fine subangular blocky structure parting to weak fine granular; friable; slightly effervescent; slightly alkaline; gradual smooth boundary.
Ab2--35 to 44 inches; black (10YR 2/1) silt loam; weak very fine subangular blocky structure parting to weak fine granular; friable; neutral; gradual smooth boundary.
Ab3--44 to 60 inches; very dark brown (10YR 2/2) silt loam; weak very fine subangular blocky structure; friable; neutral. (Combined thickness of the Ab horizon is 24 to 40 inches.)
TYPE LOCATION: Mills County, Iowa; about 3 miles northeast of Glenwood; located about 500 feet west and 75 feet north of the southeast corner of sec. 31, T. 73 N., R. 42 W.; USGS Glenwood quadrangle; lat. 41 degrees 04 minutes 25 seconds N. and long. 95 degrees 42 minutes 40 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Depth to carbonates--0 to 10 inches
Depth to buried horizons--20 to 40 inches
Content of clay in the particle-size control section (weighted average)--18 to 27 percent
Content of sand in the particle-size control section (weighted average)--less than 15 percent fine sand and sand coarser than fine sand
Ap or A horizon:
Hue--10YR
Value--3
Chroma--2 or 3
Texture--silt loam
Clay content--18 to 27 percent
Sand content--5 to 15 percent
Calcium carbonate equivalent--0 to 30 percent
Reaction--neutral to moderately alkaline
C horizon:
Hue--10YR
Value--3 to 5
Chroma--2 or 3
Texture--silt loam
Clay content--18 to 27 percent
Sand content--5 to 15 percent
Calcium carbonate equivalent--0 to 30 percent
Reaction--slightly alkaline or moderately alkaline
Redoximorphic features are most abundant just above the Ab horizon
Ab horizon:
Hue--10YR
Value--2 to 4
Chroma--1 or 2
Texture--silt loam or silty clay loam
Clay content--22 to 35 percent
Sand content--1 to 10 percent
Organic matter content--3 to 4 percent
Calcium carbonate equivalent--0 to 20 percent
Reaction--slightly acid to slightly alkaline
Bwb horizon (if it occurs):
Hue--10YR
Value--3 or 4
Chroma--1 or 2
Texture--silt loam or silty clay loam
Clay content--22 to 35 percent
Sand content--1 to 10 percent
Calcium carbonate equivalent--0 to 20 percent
Reaction--slightly acid to slightly alkaline
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Parent material--alluvium
Landform--flood plains
Slopes--0 to 2 percent
Elevation--650 to 1,100 feet above sea level
Mean annual air temperature--47 to 52 degrees F
Mean annual precipitation--26 to 34 inches
Frost-free period--145 to 175 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Kennebec,
McPaul, and
Napier soils.
Kennebec--are in landscape positions similar to those of Rawles soils, have a mollic epipedon that are more than 40 inches thick, and have a saturated zone between depths of 3 to 6 feet during April to June in normal years
McPaul--are in landscape positions similar to those of Rawles soils and have 10 to 18 percent clay in the particle-size control section
Napier--are on foot slopes adjacent to uplands, have a mollic epipedon 24 to 40 inches thick, and do not have a saturated zone within a depth of 6 feet in normal years
DRAINAGE AND PERMEABILITY:
Drainage class--moderately well drained--a saturated zone occurs at depths between 2 to 4 feet during March to June in normal years and is considered apparent
Permeability--moderate
Surface runoff potential--low
Flooding--occasional or rare flooding for brief or very brief periods during the months of February to November from precipitation events and snowmelt
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn and soybeans. The native vegetation is big bluestem, indiangrass, switchgrass, and other grasses of the tall grass prairie.
DISTRIBUTION AND EXTENT:
LRR M, MLRAs 105 and 107; southwestern Iowa and southeastern Minnesota. This series is of small extent
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Mills County, Iowa, 1979.
REMARKS:
Particle-size control section--the zone from a depth of 10 to 40 inches (C, Ab1, and Ab2 horizons);
series control section--the zone from the surface to a depth of 60 inches (Ap, C, Ab1, Ab2, and Ab3).
Diagnostic horizons and features recognized in this pedon:
ochric epipedon--the zone from the surface to a depth of 8 inches (Ap horizon);
buried layers with 3 to 4 percent organic matter--the zone from a depth of 26 to 60 inches (Ab1, Ab2, and Ab3 horizons);
udic moisture regime.
Cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
Taxonomy version--second edition, 1999.
The Rawles soils have been included with the McPaul soils in previous surveys.
ADDITIONAL DATA:
Laboratory data--Iowa State University, Ames, Iowa - data on the typical pedon.