LOCATION KEOSAUQUA IAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Typic Argiudolls
TYPICAL PEDON: Keosauqua loam, on a stream terrace with a slope of about 2 percent in a cultivated field at an elevation of 610 feet above mean sea level. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 7 inches; very dark grayish brown (10YR 3/2) loam, dark grayish brown (10YR 4/2) dry; weak very fine and fine granular structure; friable; few fine roots; slightly acid; abrupt smooth boundary.
A--7 to 13 inches; very dark grayish brown (10YR 3/2) loam, dark grayish brown (10YR 4/2) dry; weak very fine and fine subangular blocky structure; friable; few fine roots; slightly acid; clear smooth boundary. (Combined thickness of the A horizons is 10 to 20 inches.)
Bt1--13 to 22 inches; brown (10YR 4/3) loam; moderate very fine and fine angular blocky structure; friable; few fine roots; many faint dark brown (10YR 3/3) organic coats on faces of peds and in pores, and few clay films on faces of peds; slightly acid; clear smooth boundary.
Bt2--22 to 34 inches; dark yellowish brown (10YR 4/4) clay loam; moderate very fine and fine angular blocky structure; friable; few fine roots; many faint dark yellowish brown (10YR 3/4) coats on faces of peds and in pores; many distinct clay films on faces of peds; moderately acid; gradual smooth boundary.
Bt3--34 to 41 inches; dark yellowish brown (10YR 4/6) loam; moderate fine and medium angular blocky structure; friable; few fine roots; common distinct clay films on faces of peds; slightly acid; gradual smooth boundary.
Bt4--41 to 50 inches; dark yellowish brown (10YR 4/6) loam; weak medium prismatic structure parting to weak fine and medium subangular blocky; friable; few fine roots; few faint clay films on faces of peds; slightly acid; clear smooth boundary. (Combined thickness of the Bt horizons is 18 to 45 inches thick.)
2C1--50 to 62 inches; dark yellowish brown (10YR 4/6) loamy sand; single grain; loose; about 1 percent pebbles; slightly acid; gradual smooth boundary.
2C2--62 to 80 inches; dark yellowish brown (10YR 4/4) loamy sand; single grain; loose; about 5 percent pebbles; slightly acid.
TYPE LOCATION: Van Buren County, Iowa; about 2 miles northwest of Douds; 800 feet east and 1100 feet south of the northwest corner of Sec. 22, T. 70 N., R. 11 W.; USGS Douds, IA quad; lat. 40 degrees 51 minutes 15 seconds N. and long. 92 degrees 7 minutes 6 seconds W., NAD 27.
RANGE IN CHARACTERISTICS:
Mollic epipedon thickness: 10 to 20 inches
Depth to sandy alluvium: 40 to 60 inches
Depth to carbonates: more than 80 inches
Particle-size control section (weighted average):
Clay content: 18 to 35 percent
Sand content: 20 to 50 percent
Ap and A horizon:
Hue: 10YR
Value: 2 or 3
Chroma: 1 to 3
Texture: loam
Clay content: 12 to 24 percent
Sand content: 30 to 50 percent
Reaction: moderately acid to neutral
Some pedons have AB or BA horizons
Bt horizon:
Hue: 7.5 YR or 10YR
Value: 3 to 5
Chroma: 3 to 6
Texture: loam, clay loam or silt loam
Clay content: 18 to 35 percent
Sand content: 20 to 50 percent
Reaction: moderately acid to neutral
BC horizon (if present):
Hue: 7.5YR or 10YR
Value: 3 to 5
Chroma: 3 to 8
Texture: loam, silt loam, clay loam, or sandy loam
Clay content: 15 to 30 percent
Sand content: 30 to 60 percent
Reaction: moderately acid to neutral
2C horizon:
Hue: 7.5YR or 10YR
Value: 4 to 8
Chroma: 2 to 6
Texture: loamy sand, loamy fine sand, or sand
Clay content: 2 to 10 percent
Sand content: 80 to 90 percent, dominantly fine and medium sand
Rock fragment content: 1 to 10 percent fine gravel
Reaction: slightly acid or neutral
COMPETING SERIES: These are the
Atkinson,
Burchard,
Calmar,
Cokato,
Cresent,
Cresco,
Durand,
Friesland,
Griswold,
Hitt,
Hochheim,
Jasper,
Joslin,
Kishwaukee,
Marbletown,
Markesan,
Moingona,
Morrill,
Nuxmaruhanixete (T),
Pana,
Parmod,
Penfield,
Plattville,
Reedslake,
Ringwood,
Rockton,
Rotamer,
Schoolcraft,
Shelby,
Sibleyville,
Velma,
Winnebago, and
Wyanet series.
Atkinson: have limestone bedrock within 45 inches
Burchard: soils formed entirely in glacial till and do not have a lithologic discontinuity
Calmar: have limestone bedrock within 40 inches
Cokato: have 35 to 45 percent sand in the lower part of the series control section
Cresent: have 10 to 32 percent clay in the upper and middle part of the control section and have reaction range of moderately acid to moderately alkaline in the lower part of the series control section
Cresco: have less sand in the lower part of the series control section
Durand: have less sand in the lower part of the series control section
Friesland: have less sand in the lower part of the series control section
Griswold: formed entirely in calcareous sandy loam glacial till and do not have a lithologic discontinuity
Hitt: have limestone bedrock within 60 inches
Hochheim: have calcium carbonate equivalent range of 40 to 60 percent in the lower part of the series control section
Jasper: have 45 to 70 percent sand in the lower part of the series control section
Joslin: have subhorizons with 35 to 50 percent clay in the series control section
Kishwaukee: have 30 to 70 percent gravel in the lower part of the series control section
Marbletown: have sandstone or shale bedrock within 60 inches
Markesan: have 12 to 60 percent gravel in the lower part of the series control section
Moingona: formed entirely in colluvium or alluvium and do not have a lithologic discontinuity
Morill: have less sand in the lower part of the series control section
Nuxmaruhanixete (T): have more than 10 percent gravel in the lower part of the series control section
Pana: have more than 10 percent gravel in the lower part of the series control section
Parmod: have calcium carbonate equivalent range of 15 to 40 percent in the lower part of the series control section
Penfield: have 45 to 70 percent sand in the lower part of the series control section
Plattville: have limestone bedrock within 60 inches
Reedslake: formed entirely in calcareous loamy glacial till and do not have a lithologic discontinuity
Ringwood: have 10 to 40 percent rock fragments in the lower part of the series control section
Rockton: have limestone bedrock within 40 inches
Rotamer: formed entirely in calcareous sandy loam glacial till and do not have a lithologic discontinuity
Schoolcraft: have sand and gravelly sand at depths of less than 40 inches
Shelby: formed entirely in glacial till and do not have a lithologic discontinuity
Sibleyville: have sandstone or sandy and silty shale bedrock within 40 inches
Velma: contain more clay in the lower part of the series control section
Winnebago: have less sand in the lower part of the series control section
Wyanet: have 10 to 20 percent clay in the lower part of the series control section
GEOGRAPHIC SETTING:
Parent material: 40 to 60 inches of loamy alluvium and the underlying sandy alluvium
Landform: slightly convex slopes on low and very low stream terraces
Slopes: 1 to 3 percent
Elevation: 600 to 900 feet
Mean annual air temperature: 45 to 54 degrees F.
Mean annual precipitation: 34 to 37 inches
Frost-free period: 160 to 180 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Colo,
Coppock,
Nodaway, and
Richwood soils.
Colo: are poorly drained and are on nearly level floodplains
Coppock: are poorly and somewhat poorly drained and are on stream terraces, floodplains, footslopes, or alluvial fans
Nodaway: are moderately well drained and are on flood plains and alluvial fans
Richwood: are well drained, have less than 15 percent sand in the particle-size control section, and are on similar landscape positions
DRAINAGE AND PERMEABILITY:
Drainage: well drained
Permeability: moderate permeability in the loamy materials and rapid permeability in the underlying sandy materials
Surface runoff: low to medium
USE AND VEGETATION:
Soils are cultivated. Corn, soybeans, small grains, and legume hays are the principal crops. Native vegetation is prairie grasses.
DISTRIBUTION AND EXTENT: LRR M, MLRA 109; Along the streams in southeastern Iowa and possibly in adjoining states. They are of small extent.
MLRA OFFICE RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Van Buren County, Iowa, 1995.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Particle-size control section: the zone from 13 to 33 inches (Bt1 and Bt2 horizons);
Series control section: the zone from 0 to 60 inches;
Mollic epipedon - zone from the surface to 13 inches (Ap and A horizons);
Argillic horizon - zone from 13 to 50 inches (Bt1, Bt2, Bt3, and Bt4 horizons).
Udic moisture regime.
Cation exchange activity class is supported by lab sample number S92IA-177-002.
Taxonomic Version: Second Edition, 1999.
Keosauqua soils were named Richwood Variant or were included with Richwood soils in previous surveys.
ADDITIONAL DATA: Lab sample S92IA-177-002, NSSL.