LOCATION DONNAN IA+MNEstablished Series
TAXONOMIC CLASS: Fine-loamy over clayey, mixed, superactive, mesic Aquollic Hapludalfs
TYPICAL PEDON: Donnan loam, on a southwest-facing, convex 4 percent slope, in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 20 centimeters (0 to 8 inches); very dark brown (10YR 2/2) loam, dark grayish brown (10YR 4/2) dry; weak fine granular structure; friable; neutral; abrupt smooth boundary. [15 to 23 centimeters (6 to 9 inches) thick]
E--20 to 33 centimeters (8 to 13 inches); brown (10YR 4/3) loam; weak fine subangular blocky structure; friable; slightly acid; clear smooth boundary. [0 to 18 centimeters (0 to 7 inches) thick]
EB--33 to 46 centimeters (13 to 18 inches); dark yellowish brown (10YR 4/4) loam; moderate medium subangular blocky structure; friable; brown (10YR 4/3) coatings on faces of peds; strongly acid; clear smooth boundary. [0 to 15 centimeters (0 to 6 inches) thick]
Bt--46 to 61 centimeters (18 to 24 inches); brown (10YR 4/3) clay loam; moderate medium and fine subangular blocky structure; firm; common distinct very dark grayish brown (10YR 3/2) clay films; common fine faint dark grayish brown (10YR 4/2) redoximorphic depletions; strongly acid; abrupt smooth boundary.
2Btg1--61 to 86 centimeters (24 to 34 inches); dark gray (5Y 4/1) silty clay; moderate medium angular blocky and subangular blocky structure; very firm; many distinct very dark grayish brown (10YR 3/2) clay films; common white (10YR 8/1) dry, uncoated sand grains on faces of peds; few fine prominent brown (7.5YR 4/4) redoximorphic concentrations; strongly acid; clear smooth boundary.
2Btg2--86 to 122 centimeters (34 to 48 inches); gray (5Y 5/1) silty clay; strong medium prismatic structure parting to moderate fine subangular blocky; very firm; common distinct very dark grayish brown (10YR 3/2) clay films; few fine prominent brown (7.5YR 4/4) redoximorphic concentrations; strongly acid; clear smooth boundary. [Combined thickness of the Bt horizon is 41 to 122 centimeters (16 to 48 inches).]
2BC1--122 to 145 centimeters (48 to 57 inches); mottled strong brown (7.5YR 5/6) and grayish brown (2.5Y 5/2) loam; moderate coarse and extremely coarse prismatic structure dissected by few oblique fractures; firm; about 4 percent rock fragments; slightly acid; clear smooth boundary. [15 to 38 centimeters (6 to 15 inches) thick]
2BC2--145 to 152 centimeters (57 to 60 inches); yellowish brown (10YR 5/4) loam; moderate coarse and extremely coarse prismatic structure dissected by few oblique fractures; very firm; about 4 percent rock fragments; common fine distinct grayish brown (2.5Y 5/2) redoximorphic depletions; slightly acid.
TYPE LOCATION: Major Land Resource Area (MLRA) 104-Eastern Iowa and Minnesota Till Prairies; Fayette County, Iowa subset; about 2 1/2 miles north of Randalia; about 84 meters (275 feet) west and 17 meters (55 feet) south of the northeast corner of section 3, T. 93 N., R. 9 W.; USGS Hawkeye quadrangle; lat. 42 degrees 54 minutes 22 seconds N. and long. 91 degrees 53 minutes 7 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Depth to clayey paleosol--50 to 91 centimeters (20 to 36 inches)
Content of clay in the particle-size control section (weighted average)--25 to 35 percent in the upper part and 40 to 55 percent in the lower part
Content of sand in the particle-size control section (weighted average)--25 to 35 percent
A or Ap horizon:
Hue--10YR
Value--2 or 3
Chroma--1 or 2
Texture--loam or silt loam
Clay content--18 to 26 percent
Sand content--20 to 35 percent
Reaction--moderately acid to neutral
E or EB horizon:
Hue--10YR
Value--4 or 5
Chroma--2 to 4
Texture--loam to silt loam
Clay content--20 to 26 percent
Sand content--25 to 35 percent
Reaction--strongly acid to slightly acid
Bt horizon:
Hue--10YR or 2.5Y
Value--4 or 5
Chroma--3 or 4
Texture--clay loam, loam, or silty clay loam
Clay content--20 to 30 percent
Sand content--15 to 35 percent
Reaction--strongly acid to slightly acid
2Btg horizon:
Hue--5Y or 2.5Y
Value--3 to 6
Chroma--1 or 2
Texture--silty clay or clay
Clay content--42 to 55 percent
Sand content--15 to 35 percent
Reaction--strongly acid to slightly acid
Some pedons have a thin, less than 15 centimeters (6 inches) thick, layer of sandy loam above the 2Bt horizon
2BC horizon:
Hue--7.5YR, 10YR, or 2.5Y
Value--4 to 5
Chroma--2 to 8
Texture--loam
Clay content--18 to 27 percent, mean of 22 percent
Sand content--35 to 50 percent, mean of 44 percent
Reaction--slightly acid to moderately alkaline
Rock fragment content--2 to 12 percent
Moist bulk density--1.75 g/cc to 1.90 g/cc
COMPETING SERIES:
No other series are in this family.
GEOGRAPHIC SETTING:
Parent material--50 to 91 centimeters (20 to 36 inches) of loamy sediments and the underlying highly weathered paleosol that developed in glacial till
Landform--convex ridges and side slopes on dissected till plains
Slopes--0 to 9 percent
Elevation--290 to 427 meters (950 to 1400 feet) above sea level
Mean annual air temperature--7 to 10 degrees C (45 to 50 degrees F)
Mean annual precipitation--76 to 86 centimeters (30 to 34 inches)
Frost-free period--145 to 165 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Cresco,
Clyde,
Floyd, and
Kenyon soils.
Cresco--are at higher elevations on convex ridges on interfluves, have very firm consistence in the middle third of the series control section, and have less than 35 percent clay in the particle-size control section
Clyde--are at higher elevations on nearly level positions on interfluves and are on concave drainageways at lower elevations and have a frequently saturated zone within 0.3 meters (0 to 1 foot) in normal years
Floyd--are in landscape positions similar to those of the Donnan soils, have a mollic epipedon 41 to 61 centimeters (16 to 24 inches) thick and have a frequently saturated zone within depths of 0.3 to 1.1 meters (1.0 to 3.5 feet) in normal years
Kenyon--are at higher elevations on convex ridges on interfluves and have less than 30 percent clay in the particle-size control section
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--somewhat poorly drained--a frequently saturated zone occurs within depths of 0.5 to 0.9 meters (1.5 to 3 feet) during the wettest portions of normal years is considered perched
Saturated hydraulic conductivity--moderately high in the loamy sediments and low in the underlying highly weathered paleosol
Surface runoff potential--medium
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn, soybeans, small grains, and legume hay. Native vegetation is deciduous trees and big bluestem, little bluestem, switchgrass, other grasses of the tall grass prairie.
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic section(s)--Dissected till plains
MLRA(s)--Eastern Iowa and Minnesota Till Prairies (104); Iowa erosional surface
LRR M; northeastern Iowa and southeastern Minnesota
Extent--moderate
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Howard County, Iowa, 1970.
REMARKS:
Particle-size control section--the zone from a depth of 46 to 96 centimeters (18 to 38 inches) (Bt, 2Btg1, and 2Btg2 horizons);
series control section--the zone from the surface to a depth of 150 centimeters (59 inches) (Ap, E, EB, Bt, 2Btg1, 2Btg2, 2C1, and 2C2 horizons).
Diagnostic horizons and features recognized in this pedon:
ochric epipedon--the zone from the surface to a depth of 46 centimeters (0 to 18 inches) (Ap, E and EB horizons);
argillic horizon--the zone from a depth of 33 to 122 centimeters (18 to 48 inches) (Bt, 2Btg1, and 2Btg2 horizons);
udic moisture regime.
Cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
Taxonomy version--Keys to Soil Taxonomy, ninth edition, 2003.