LOCATION ONAWA IA+KS MO NE SDEstablished Series
TAXONOMIC CLASS: Clayey over loamy, smectitic over mixed, superactive, calcareous, mesic Aquertic Udifluvents
TYPICAL PEDON: Onawa silty clay, on a nearly level flood plain, in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 7 inches; very dark grayish brown (2.5Y 3/2) silty clay; moderate fine subangular blocky structure; firm; slightly alkaline; abrupt smooth boundary. (6 to 10 inches thick)
Cg1--7 to 22 inches; dark grayish brown (2.5Y 4/2) silty clay; massive with weak, thin alluvial stratification; firm; 1 inch layer of silty clay loam at 18 to 19 inches; few fine prominent red (2.5YR 5/8) and strong brown (7.5YR 5/8) redoximorphic concentrations; slightly effervescent; slightly alkaline; clear smooth boundary. (12 to 20 inches thick)
2Cg2--22 to 60 inches; dark grayish brown (10YR 4/2) and very dark gray (10YR 3/1) silt loam; massive; firm; few fine prominent strong brown (7.5YR 5/6) and few fine distinct reddish brown (5YR 4/3) redoximorphic concentrations; strongly effervescent; slightly alkaline.
TYPE LOCATION: Monona County, Iowa; about 50 feet west and 1,980 feet north of the southeast corner of sec. 1, T. 84 N., R. 47 W.; USGS Macy quadrangle; lat. 42 degrees 7 minutes 26 seconds N. and long. 96 degrees 15 minutes 8 seconds W., NAD 27
RANGE IN CHARACTERISTICS:
Depth to carbonates--0 to 10 inches
Depth to loamy alluvium--18 to 30 inches
Content of clay in the upper third to upper half of the particle-size control section (weighted average)--50 to 70 percent
Content of clay in the lower half to lower two thirds of the particle-size control section (weighted average)--10 to 18 percent
Content of sand in the upper third to upper half of the particle-size control section (weighted average)--1 to 5 percent fine sand and sand coarser than fine sand
Content of sand in the lower half to lower two thirds of the particle-size control section (weighted average)--10 to 75 percent fine sand and sand coarser than fine sand
A or Ap horizon:
Hue--10YR or 2.5Y
Value--2 or 3
Chroma--1 or 2
Texture--silty clay, clay, silty clay loam, loam, or silt loam
Clay content--15 to 50 percent
Sand--1 to 50 percent
Calcium carbonate equivalent--5 to 30 percent
Reaction--slightly alkaline or moderately alkaline
Overwash phase:
Texture--fine sandy loam or loamy fine sand
Clay content--2 to 20 percent
Sand content--50 to 90 percent
Thickness--10 to 20 inches
Cg horizon:
Hue--10YR, 2.5Y, 5Y, or is neutral
Value--3 to 5
Chroma--0 to 2
Texture--clay or silty clay
Clay content--50 to 70 percent
Sand--1 to 5 percent
Calcium carbonate equivalent--5 to 30 percent
Reaction--slightly alkaline or moderately alkaline
Many pedons have strata of silty or clayey materials with individual strata up to 1 to 2 inches thick
Some pedons have a transitional layer, less than 5 inches thick, between the Cg1 and 2Cg2 horizons of silty clay loam, with sand content up to 15 percent fine sand and sand coarser than fine sand
2Cg horizon:
Hue--10YR, 2.5Y, 5Y, or is neutral
Value--3 to 5
Chroma--0 to 2
Texture--silt loam, very fine sandy loam, loam with a high amount of very fine sand, or loamy very fine sand
Clay content--10 to 18 percent
Sand content--10 to 75 percent
Calcium carbonate equivalent--5 to 30 percent
Reaction--slightly alkaline or moderately alkaline
Some pedons have strata of loamy fine sand or fine sand below a depth of 40 inches
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Parent material--18 to 30 inches of clayey alluvium and the underlying loamy alluvium
Landform--flood plains
Slopes--0 to 2 percent
Elevation--700 to 1,260 feet above sea level
Mean annual air temperature--46 to 56 degrees F.
Mean annual precipitation--19 to 36 inches
Frost-free period--135 to 185 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Albaton,
Blake,
Percival,
Grable,
Haynie, and
Modale soils.
Albaton--are in the slightly lower landscape positions, have a saturated zone within a depth of 1 foot during March to June in most years, and have a clay content of 50 to 60 percent throughout the particle-size control section
Blake--are in landscape positions similar to those of the Onawa soils and have a clay content of 22 to 35 percent throughout the particle-size control section
Percival--are in the slightly higher landscape positions, have a clay content of less than 10 percent in the lower half of the particle-size control section
Grable--are in the higher landscape positions, have a clay content of 12 to 16 percent in the upper half of the particle-size control section, and do not have a saturated zone within a depth of 6 feet during April to June in most years
Haynie--are in the slightly higher landscape positions, have a clay content of 15 to 18 percent throughout the particle-size control section, and have a saturated zone between depths of 4 to 6 feet during April to June in most years
Modale--are in the slightly higher landscape positions, have a clay content of 10 to 18 percent in the upper third to upper half of the particle-size control section, and have a saturated zone between depths of 1 to 3 feet during April to June in most years
DRAINAGE AND PERMEABILITY:
Drainage class--somewhat poorly drained--a saturated zone occurs within depths of 1 to 3 feet during March to June in most years and is considered apparent
Permeability--slow in the clayey alluvium and moderate or moderately rapid in the underlying loamy alluvium
Surface runoff potentiallow or medium
Flooding--rare to occasional flooding with very brief or brief duration during the months of February to November from precipitation events and snowmelt and flooding from streambank overflow is limited where dams and levees protect areas
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn, soybeans, and small grains. Some areas are land-leveled and irrigated. The native vegetation is big bluestem, little bluestem, western wheatgrass, indiangrass, switchgrass, and other grasses of the tall grass prairie.
DISTRIBUTION AND EXTENT:
LRR M, MLRAs 102B, 107A and 107B, LRR G, MLRA 63B; along the Missouri River in Iowa, Kansas, Missouri, Nebraska, and South Dakota. This series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Boone County, Missouri, 1952.
REMARKS:
Particle-size control section--the zone from a depth of 10 to 40 inches (Cg1 and 2Cg2 horizons);
series control section--the zone from the surface to a depth of 60 inches (Ap, Cg1, and 2Cg2 horizons).
Diagnostic horizons and features recognized in this pedon:
ochric epipedon--the zone from the surface to a depth of 7 inches (Ap horizon);
udic moisture regime.
Cation-exchange activity class is supported by lab sample numbers S94NE-177-015 and S96IA-193-028, National Soil Survey Laboratory.
Taxonomy version--second edition, 1999.
ADDITIONAL DATA:
Laboratory data--Iowa State University Agricultural Experiment Station, Ames, Iowa file No. 55907-55909
Laboratory data--National Soil Survey Laboratory, Lincoln, Nebraska pedons S94NE-177-015 and S96IA-193-028 (http://ssldata.sc.egov.usda.gov/).