LOCATION ONAWET NE+KSEstablished Series
TAXONOMIC CLASS: Clayey over loamy, smectitic over mixed, superactive, calcareous, mesic Aeric Fluvaquents
TYPICAL PEDON: Onawet silty clay loam with a slope of nearly 0 percent on a nearly level flood plain; cultivated. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 18 centimeters; very dark grayish brown (10YR 3/2) silty clay loam, dark grayish brown (10YR 4/2) dry; weak fine granular structure; friable; slightly effervescent; slightly alkaline; abrupt smooth boundary. (15 to 25 centimeters thick)
Cg1--18 to 40 centimeters; dark grayish brown (2.5Y 4/2) silty clay, grayish brown (2.5Y 5/2) dry; moderate fine angular blocky structure; firm; common medium distinct dark reddish brown (5YR 3/3) redox concentrations; strongly effervescent; slightly alkaline; clear wavy boundary.
Cg2--40 to 61 centimeters; dark grayish brown (2.5Y 4/2) silty clay, grayish brown (2.5Y 5/2) dry; massive; firm; common medium distinct dark yellowish brown (10YR 4/4) redox concentrations; strongly effervescent; slightly alkaline; abrupt wavy boundary. (Combined thickness of the Cg horizons is 30 to 64 centimeters)
2Cg3--61 to 81 centimeters; dark grayish brown (2.5Y 4/2) silt loam, grayish brown (2.5Y 5/2) dry and thin strata of light brownish gray (2.5Y 6/2) dry; massive; friable; common fine distinct reddish brown (5YR 4/4) redox concentrations; strongly effervescent; slightly alkaline; clear wavy boundary.
2Cg4--81 to 99 centimeters; dark grayish brown (2.5Y 4/2) very fine sandy loam, grayish brown (2.5Y 5/2) dry and thin strata of light brownish gray (2.5Y 6/2) dry; massive; very friable; common fine distinct yellowish brown (10YR 5/6) redox concentrations; violently effervescent; slightly alkaline; clear wavy boundary.
2Cg5--99 to 142 centimeters; dark grayish brown (2.5Y 4/2) silt loam, grayish brown (2.5Y 5/2) dry; massive; friable; common fine distinct yellowish brown (10YR 5/6) redox concentrations; strongly effervescent; slightly alkaline; clear wavy boundary.
3Cg6--142 to 203 centimeters; dark grayish brown (2.5Y 4/2) loamy fine sand, grayish brown (2.5Y 5/2) dry; massive; very friable; common medium distinct yellowish brown (10YR 5/6) redox concentrations; strongly effervescent; slightly alkaline.
TYPE LOCATION: Major Land Resource Area 107B - Iowa and Missouri Deep Loess Hills, Washington County Nebraska Subset; about 4 1/2 miles east of Herman; 1800 feet east and 825 feet south of the northwest corner of sec. 25, T. 20 N., R. 11 E.; USGS Herman, Nebraska Topographic Quadrangle; latitude 41 degrees 40 minutes 51 seconds N. and longitude 96 degrees 7 minutes 41 seconds W. NAD 27.
RANGE IN CHARACTERISTICS:
Depth to lithologic discontinuity - 45 to 90 centimeters
Thickness of the solum - Less that 30 centimeters
Particle-size control section clay percents (weighted average) - 50 to 60 percent (with silty clay or clay textures) above the discontinuity, and 12 to 18 percent (with silt loam, loam, or very fine sandy loam textures) below the discontinuity.
A horizon:
Hue: 10YR or 2.5Y
Value: 3 or 4
Chroma: 1 or 2
Texture: silty clay loam, silty clay or silt loam
Clay content: 15 to 55 percent
Calcium carbonate equivalent: 5 to 30 percent
Reaction: slightly to moderately alkaline
Some pedons have an AC horizon.
Cg horizon:
Hue: 5Y, 2.5Y or 10YR
Value: 3 to 5
Chroma: 0 to 2
Texture: silty clay or clay
Clay content: 50 to 60 percent
Calcium carbonate equivalent: 5 to 30 percent
Reaction: slightly to moderately alkaline
2Cg horizon:
Hue: 5Y, 2.5Y or 10YR
Value: 4 or 5
Chroma: 0 to 2
Texture: silt loam, very fine sandy loam, or loam
Clay content: 12 to 18 percent
Calcium carbonate equivalent: 5 to 30 percent
Reaction: slightly to moderately alkaline
3Cg horizon:
Hue: 5Y, 2.5Y or 10YR
Value: 4 or 5
Chroma: 0 to 2
Texture: loamy fine sand, loamy sand or fine sand
Calcium carbonate equivalent: 5 to 30 percent
Reaction: slightly to moderately alkaline
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Parent material - calcareous alluvium
Landform - ephemeral oxbow lakes on floodplains of the Missouri River
Slopes - 0 to 1 percent
Elevation - 275 to 335 meters
Mean annual air temperature - 9 to 13 degrees C
Mean annual precipitation - 610 to 910 millimeters
Frost-free period - 150 to 175 days
GEOGRAPHICALLY ASSOCIATED SOILS:
Albaton - are on similar topography and in the fine particle-size class.
Blake - are on slightly higher topography and in the fine-silty particle-size class.
Onawa - are on slightly higher topography and in the Aquertic Udifluvents Subgroup.
Percival - are on slightly higher topography and are somewhat poorly drained.
Grable - are on higher landscape positions, in the coarse-silty over sandy or sandy-skeletal particle size class, and in the Mollic Udifluvents Subgroup.
Haynie - are on higher landscape positions, in the coarse-silty particle-size class, and in the Mollic Udifluvents Subgroup.
Sarpy are on higher landscape positions, and in the Typic Udipsamments Subgroup.
Wathena - are on higher landscape positions, in the sandy particle-size class, and in the Mollic Udifluvents Subgroup.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage - 15 centimeters above the surface to 30 centimeters below the surface all year (very poorly drained)
Runoff - Very slow
Saturated Hydraulic Conductivity: Slow in the upper part and moderate or moderately rapid in the lower part
Flooding: Occasional to frequent, and duration is brief to long
USE AND VEGETATION: Most areas are cropped to corn and soybeans. Native vegetation is tall, water tolerant prairie grasses, and cottonwood and willow trees.
DISTRIBUTION AND EXTENT:
Physiographic Division Interior Plains
Physiographic Province Central Lowland
Physiographic Section Dissected Till Plains
Local Physiographic Area - Flood plain of the Missouri River
Land Resource Region Central Feed Grains and Livestock Region (LRR M)
Major Land resource Area Iowa and Missouri Deep Loess Hills (MLRA 107B)
Onawet soils are of small extent; to date, 2,473 acres are correlated.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Washington County, Nebraska, 2003. The named is coined.
REMARKS:
Diagnostic horizons and features recognized in the typical pedon are:
Particle-size control section - 25 to 100 centimeters (Cg1, Cg2, 2Cg3, 2Cg4 horizons)
Ochric epipedon - 0 to 18 centimeters (Ap horizon)
Other features - strongly contrasting particle size classes within the control section.
Soil moisture regime: Aquic
Remarks: These soils were originally mapped as Rauville in the previous Washington County Nebraska soil survey. The Rauville soils are frigid.
The assignment of the cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.