LOCATION KEOMAH IA+ILEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Aeric Endoaqualfs
TYPICAL PEDON: Keomah silt loam, on a slope of about 2 percent, in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 20 centimeters; dark grayish brown (10YR 4/2) silt loam, light brownish gray (10YR 6/2) dry; weak fine granular structure; friable; common faint dark gray (10YR 4/1) coats on faces of peds; moderately acid; abrupt smooth boundary. (15 to 20 centimeters thick)
E--20 to 38 centimeters; grayish brown (10YR 5/2) silt loam with some dark gray (10YR 4/1) on faces of peds; light gray (10YR 7/2) dry; weak thin platy structure; friable; few fine distinct brown (7.5YR 4/4) redoximorphic concentrations; moderately acid; clear smooth boundary. (10 to 25 centimeters thick)
BE--38 to 46 centimeters; brown (10YR 5/3) silty clay loam; moderate fine and very fine subangular blocky structure; friable; few faint dark grayish brown (10YR 4/2) clay films on faces of peds; common distinct light brownish gray (10YR 6/2) dry, silt coats on faces of peds; few fine black (10YR 2/1) iron and manganese concretions; few fine distinct dark gray (10YR 4/1) redoximorphic depletions; strongly acid; gradual smooth boundary. (0 to 10 centimeters thick)
Bt1--46 to 64 centimeters; brown (10YR 5/3) silty clay; moderate fine subangular blocky structure; firm; common distinct dark grayish brown (10YR 4/2) clay films on faces of peds; common distinct light brownish gray (10YR 6/2) dry, silt coats on faces of peds; few fine black (10YR 2/1) iron and manganese concretions; common fine distinct strong brown (7.5YR 5/6) redoximorphic concentrations; strongly acid; gradual smooth boundary.
Bt2--64 to 91 centimeters; about 60 percent brown (10YR 5/3) and about 40 percent grayish brown (10YR 5/2) silty clay; moderate fine and medium subangular blocky structure; firm; many distinct dark grayish brown (10YR 4/2) clay films of faces of peds; few distinct light brownish gray (10YR 6/2) silt coats on faces of peds; few fine prominent strong brown (7.5YR 5/6) redoximorphic concentrations; strongly acid; gradual smooth boundary. (Combined thickness of the Bt horizon is 20 to 60 centimeters.)
Btg1--91 to 114 centimeters; grayish brown (2.5Y 5/2) silty clay loam; weak medium prismatic structure parting to moderate medium angular blocky; firm; many faint dark grayish brown (2.5Y 4/2) clay films on faces of peds; many fine and medium prominent strong brown (7.5YR 5/6) and yellowish brown (10YR 5/8) redoximorphic concentrations; strongly acid; gradual smooth boundary.
Btg2--114 to 135 centimeters; grayish brown (2.5Y 5/2) silty clay loam; weak medium prismatic structure parting to weak fine and medium subangular blocky; friable; few distinct gray (2.5Y 5/1) clay films on faces of peds; few fine black (10YR 2/1) concretions (iron and manganese oxides); many medium prominent strong brown (7.5YR 5/6) and yellowish brown (10YR 5/8) redoximorphic concentrations; strongly acid; gradual smooth boundary. (Combined thickness of the Btg horizon is 20 to 60 centimeters.)
BCg--135 to 163 centimeters; grayish brown (2.5Y 5/2) silty clay loam; weak medium prismatic structure; friable; few fine black (10YR 2/1) concretions (iron and manganese oxides); common medium prominent strong brown (7.5YR 5/6) redoximorphic concentrations; slightly acid; gradual smooth boundary. (0 to 46 centimeters thick)
Cg--163 to 203 centimeters; grayish brown (2.5Y 5/2) silt loam; massive; friable; few fine black (10YR 2/1) concretions (iron and manganese oxides); common medium prominent strong brown (7.5YR 5/6) redoximorphic concentrations; slightly acid.
TYPE LOCATION: Major Land Resource Area (MLRA) 108C-Illinois and Iowa Deep Loess and Drift, West Central Part; Washington County, Iowa subset; about 1 mile north and 10 miles west of Washington; about 2,600 feet south and 2,075 feet west of the northeast corner of section 9, T. 75 N., R. 9 W.; USGS Keota quadrangle; lat. 41 degrees 18 minutes 58.7 seconds N. and long. 91 degrees 53 minutes 43.1 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Depth to carbonates--greater than 150 centimeters
Clay content in the particle-size control section (weighted average)--36 to 42 percent
Sand content in the particle-size control section (weighted average)--less than 7 percent
A horizon (when present):
Hue--10YR
Value--3
Chroma--1
Texture--silt loam
Clay content--20 to 27 percent
Sand content--less than 5 percent
Reaction--moderately acid to neutral
Thickness--2 to 8 centimeters
Ap horizon:
Hue--10YR
Value--4
Chroma--1 or 2
Texture--silt loam
Clay content--20 to 27 percent
Sand content--less than 5 percent
Reaction--moderately acid to neutral
E horizon:
Hue--10YR
Value--4 or 5
Chroma--1 to 3
Texture--silt loam
Clay content--15 to 25 percent
Sand content--less than 5 percent
Reaction--strongly acid to neutral
BE horizon (if present):
Hue--10YR
Value--4 or 5
Chroma--2 or 3
Texture--silt loam or silty clay loam
Clay content--22 to 30 percent
Sand content--less than 5 percent
Reaction--strongly acid to neutral
Bt horizon:
Hue--10YR
Value--4 or 5
Chroma--3 or 4
Texture--silty clay loam or silty clay
Clay content--36 to 42 percent
Sand content--less than 5 percent
Reaction--very strongly acid to slightly acid
Btg horizon:
Hue--10YR, 2.5Y, or 5Y
Value--4 to 6
Chroma--2 or 3
Texture--silty clay loam or silty clay
Clay content--36 to 42 percent
Sand content--less than 5 percent
Reaction--very strongly acid to slightly acid
BCg and Cg horizons:
Hue--10YR, 2.5Y, or 5Y
Value--4 to 6
Chroma--2 to 6
Texture--silty clay loam or silt loam
Clay content--20 to 30 percent
Sand content--less than 5 percent
Reaction--strongly acid to neutral
COMPETING SERIES:
There are no series in the same family.
GEOGRAPHIC SETTING:
Parent material--loess
Landform--summits of interfluves, head slopes on dissected till plains, and treads on stream terraces
Slope--0 to 5 percent
Elevation--198 to 411 meters above sea level
Mean annual air temperature--9 to 11 degrees C
Mean annual precipitation--810 to 920 millimeters
Frost-free period--165 to 180 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Clinton,
Givin, and
Lindley soils.
Clinton--are at lower elevations on side slopes and have frequently saturated zone at a depth of 1.2 meters in normal years
Givin--are in landscape positions similar to those of the Keomah soils and have a dark-colored surface horizon
Lindley--are at lower elevations on side slopes and have more than 30 percent sand throughout the series control section
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--somewhat poorly drained-a frequently saturated zone occurs at a depth of 0.3 meter during March to June in normal years and is considered apparent
Saturated hydraulic conductivity--1.4 to 14 micrometers per second
Surface runoff potential--negligible to low
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn, soybeans, small grains, and legume hays. A few areas are wooded. The native vegetation is deciduous trees.
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior plains
Physiographic Province--Central lowlands
Physiographic sections--Dissected till plains and Till plains
MLRAs--Illinois and Iowa Deep Loess and Drift (108),
Iowa and Missouri Heavy Till Plain (109),
Southern Illinois and Indiana Thin Loess and Till Plain (114), and
Central Mississippi Valley Wooded Slopes (115)
LRR M; southeastern Iowa and western Illinois
Extent--large
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Jefferson County, Iowa, 1957.
REMARKS:
Particle-size control section--the zone from a depth of 46 to 96 centimeters (Bt1, Bt2, and Btg1 horizons);
series control section--the zone from the surface to a depth of 150 centimeters (Ap, E, BE, Bt1, Bt2, Btg1, Btg2, and BCg horizons).
Diagnostic horizons and features recognized in this pedon:
ochric epipedon--the zone from the surface to a depth of 38 centimeters (Ap and E horizons);
argillic horizon--the zone from a depth of 46 to 135 centimeters (Bt1, Bt2, Btg1 and Btg2 horizons);
aquic moisture regime.
Taxonomy version--Keys to Soil Taxonomy, ninth edition, 2003.