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 186 meters above mean sea level. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 18 centimeters; 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--18 to 33 centimeters; 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 horizon is 25 to 49 centimeters.)
Bt1--33 to 56 centimeters; brown (10YR 4/3) loam; moderate very fine and fine angular blocky structure; friable; few fine roots; few distinct clay films on faces of peds; many distinct dark brown (10YR 3/3) organic coats on faces of peds and in pores; slightly acid; clear smooth boundary.
Bt2--56 to 86 centimeters; dark yellowish brown (10YR 4/4) clay loam; moderate very fine and fine angular blocky structure; friable; few fine roots; many distinct clay films on faces of peds; many distinct dark yellowish brown (10YR 3/4) coats on faces of peds and in pores; moderately acid; gradual smooth boundary.
Bt3--86 to 104 centimeters; 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--104 to 127 centimeters; 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 horizon is 45 to 120 centimeters.)
2C1--127 to 158 centimeters; dark yellowish brown (10YR 4/6) loamy sand; single grain; loose; about 1 percent pebbles; slightly acid; gradual smooth boundary.
2C2--158 to 200 centimeters; dark yellowish brown (10YR 4/4) loamy sand; single grain; loose; about 5 percent pebbles; slightly acid.
TYPE LOCATION: Major Land Resource Area (MLRA) 109-Iowa and Missouri Heavy Till Plain, Van Buren County, Iowa subset; about 2 miles northwest of Douds; located about 800 feet east and 1,100 feet south of the northwest corner of section 22, T. 70 N., R. 11 W.; USGS Douds topographic quadrangle; lat. 40 degrees 51 minutes 15 seconds N. and long. 92 degrees 7 minutes 7 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Mollic epipedon thickness--25 to 49 centimeters
Depth to sandy alluvium--100 to 150 centimeters
Depth to carbonates--more than 200 centimeters
Clay content in the particle-size control section (weighted average)--18 to 30 percent
Sand content in the particle-size control section (weighted average)--20 to 50 percent
Ap and A horizon:
Hue--10YR
Value--2 or 3
Chroma--1 to 3
Texture--loam
Clay content--10 to 24 percent
Sand content--30 to 50 percent
Reaction--moderately acid to neutral
Some pedons have AB or BA horizons
Bt horizon:
Hue--7.5YR or 10YR
Value--3 to 5
Chroma--3 to 6
Texture--loam, clay loam or silt loam
Clay content--18 to 30 percent
Sand content--25 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 95 percent
Rock fragment content--1 to 10 percent, fine gravel
Calcium carbonate equivalent--0 percent
Reaction--slightly acid or neutral
COMPETING SERIES: These are the
Atkinson,
Burchard,
Cokato,
Cresco,
Cresent,
Durand,
Friesland,
Griswold,
Hitt,
Jasper,
Joslin,
Kishwaukee,
Marbletown,
Moingona,
Morrill,
Nuxmaruhanixete ,
Pana,
Parmod,
Penfield,
Reedslake,
Ringwood,
Rockton,
Schoolcraft,
Shelby,
Sibleyville,
Velma, and
Winnebago series.
Atkinson--have a lithic contact with limestone within a depth of 150 centimeters
Burchard--have carbonates within a depth of 76 centimeters
Cokato--have carbonates within a depth of 122 centimeters
Cresco--have a sand content that averages 35 to 50 percent in the lower third of the particle-size control section
Cresent--differentia is not clear between the Keosauqua and Cresent series, see remarks
Durand--have matrix hues redder than 10YR in the lower half of the particle-size control section
Friesland--have a sand content of less than 10 percent in the third part of the series control section
Griswold--have a sand content of 55 to 80 percent in the lower third of the series control section
Hitt--have a lithic contact with limestone within a depth of 150 centimeters
Jasper--have a sand content that averages 45 to 70 percent in the lower third of the series control section
Joslin--have subhorizons with a clay content of 35 to 50 percent in the series control section
Kishwaukee--have a rock fragment content of 30 to 70 percent gravel in the lower part of the series control section
Marbletown--have a paralithic contact with sandstone or shale within a depth of 150 centimeters
Moingona--have a sand content that averages 35 to 70 percent in the lower third of the series control section
Morrill--have matrix hues redder than 7.5YR in the upper part of the argillic horizon
Nuxmaruhanixete--have a rock fragment content of more than 15 percent gravel in the lower half of the series control section
Pana--have a rock fragment content of more than 15 percent gravel in the lower half 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 a clay content of 5 to 20 percent and a sand content of 45 to 70 percent in the lower half of the series control section
Reedslake--have a clay content of 22 and 30 percent in the lower third of the series control section
Ringwood--have a rock fragment content of 10 to 40 percent in the lower part of the series control section
Rockton--have a lithic contact with limestone within a depth of 100 centimeters
Schoolcraft--have a sand content of more than 70 percent within a depth of 100 centimeters
Shelby--average 30 to 35 percent clay in the particle-size control section
Sibleyville--have a paralithic contact with sandstone or sandy and silty shale bedrock within a depth of 100 centimeters
Velma--have carbonates in the lower third of the series control section
Winnebago--have matrix hues of 5YR or redder in at least one subhorizon of the argillic horizon
GEOGRAPHIC SETTING:
Parent material--100 to 150 centimeters of loamy alluvium and the underlying sandy alluvium
Landform--slightly convex slopes on low and very low stream terraces in river valleys
Slope--1 to 3 percent
Elevation--180 to 300 meters above sea level
Mean annual air temperature--9 to 12 degrees C
Mean annual precipitation--865 to 1,040 millimeters
Frost-free period--175 to 210 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Colo,
Coppock,
Nodaway, and
Richwood soils.
Colo--are on lower landscape positions on floodplains and are frequently saturated from the soil surface to a depth of 0.3 meters during the wettest period of years when precipitation is within one standard deviation of the 30 year mean of annual precipitation
Coppock--are on lower landscape positions on floodplains, stream terraces, foot slopes, and alluvial fans and are frequently saturated from the soil surface to a depth of 0.3 meters during the wettest period of years when precipitation is within one standard deviation of the 30 year mean of annual precipitation
Nodaway--on lower landscape positions on floodplains and alluvial fans and have a sand content of less than 15 percent throughout the series control section
Richwood--are on landscape positions similar to those of the Keosauqua soils and have a sand content that averages less than 15 percent in the particle-size control section
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage--well drained--a frequently saturated zone does not occur within a depth of 1.8 meters during the wettest period of years when precipitation is within one standard deviation of the 30 year mean of annual precipitation
Saturated hydraulic conductivity--1.0 to 10.0 micrometers per second in the loamy materials and 10 to 100 micrometers per second in the underlying sandy materials
Flooding--rarely flooded for brief duration
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn, soybeans, small grains, and hay. The native vegetation is big bluestem, indiangrass, switchgrass, and other grasses of the tall grass prairie.
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic sections--Dissected till plains
MLRAs--Iowa and Missouri Heavy Till Plain (109)
LRR M; southeastern Iowa
Extent--small
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana; MLRA SSO 10-12 (Fairfield, Iowa)
SERIES ESTABLISHED: Van Buren County, Iowa, 1995.
REMARKS:
Particle-size control section--the zone from a depth of 33 to 83 centimeters;
series control section--the zone from the surface to a depth of 150 centimeters.
Diagnostic horizons and features recognized in this pedon include:
mollic epipedon--the zone from the surface to a depth of 33 centimeters (Ap and A horizons);
argillic horizon--the zone from a depth of 33 to 127 centimeters (Bt1, Bt2, Bt3, and Bt4 horizons);
udic moisture regime.
Several property ranges of the Keosauqua and Cresent series overlap. Further study is needed to clearly differentiate these two series.
Cation exchange activity class is supported by lab sample number S92IA-177-002.
Taxonomic Version--Keys to Soil Taxonomy, tenth edition, 2006.
Keosauqua soils were previously identified as Richwood Variant or were included with Richwood soils.
ADDITIONAL DATA:
Laboratory data--National Soil Survey Laboratory, Lincoln, Nebraska - user pedon ID 92IA177002 (http://ssldata.nrcs.usda.gov/).