LOCATION DUNKERTON IA+MNEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, mesic Aquollic Hapludalfs
TYPICAL PEDON: Dunkerton sandy loam, on a north-facing, convex slope of 3 percent, in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 23 centimeters (0 to 9 inches); very dark grayish brown (10YR 3/2) sandy loam, dark grayish brown (10YR 4/2) dry; weak fine granular structure; friable; common fine roots; common fine tubular pores; neutral; abrupt smooth boundary. [13 to 23 centimeters (5 to 9 inches) thick]
BE--23 to 38 centimeters (9 to 15 inches); about 50 percent dark grayish brown (10YR 4/2) and about 50 percent brown (10YR 4/3) sandy loam; weak thick platy and weak fine subangular blocky structure; friable; common fine roots; common fine tubular pores; slightly acid; clear smooth boundary. [5 to 20 centimeters (2 to 8 inches) thick]
Bt1--38 to 64 centimeters (15 to 25 inches); brown (7.5YR 4/4) sandy loam; weak fine subangular blocky structure; friable; common very fine roots; common fine tubular pores; few distinct dark grayish brown (10YR 4/2) clay films on vertical faces of peds; common fine distinct grayish brown (10YR 5/2) redoximorphic depletions; discontinuous stone line consisting of rounded rock fragments 2 to 150 millimeters (up to 6 inches) in diameter (5 to 10 percent of this horizon); slightly acid; abrupt smooth boundary. [15 to 46 centimeters (6 to 18 inches) thick]
2Bt2--64 to 91 centimeters (25 to 36 inches); about 60 percent strong brown (7.5YR 5/6) and about 40 percent light brownish gray (10YR 6/2) sandy clay loam; weak fine and medium subangular blocky structure; firm; few very fine roots; few distinct dark grayish brown (10YR 4/2) clay films on vertical faces of peds; common fine very dark brown (10YR 2/2) masses of iron-manganese; about 2 percent subrounded mixed rock fragments (2 to 75 millimeters in diameter); moderately acid; gradual smooth boundary.
2Bt3--91 to 124 centimeters (36 to 49 inches); about 50 percent strong brown (7.5YR 5/6) and about 50 percent light brownish gray (10YR 6/2) loam; weak fine prismatic structure; firm; few distinct dark grayish brown (10YR 4/2) clay films on vertical faces of peds; common fine very dark brown (10YR 2/2) masses of iron-manganese; common fine distinct yellowish brown (10YR 5/6) redoximorphic concentrations; about 2 percent subrounded mixed rock fragments (2 to 75 millimeters in diameter); strongly acid; gradual wavy boundary. [Combined thickness of the 2Bt horizon is 30 to 91 centimeters (12 to 36 inches).]
2BC--124 to 203 centimeters (49 to 80 inches); about 50 percent strong brown (7.5YR 5/6) and about 50 percent pinkish gray (7.5YR 6/2) loam; extremely coarse prismatic structure dissected by few oblique fractures; very firm; common fine very dark brown (10YR 2/2) masses of iron-manganese; common fine prominent reddish brown (5YR 4/4) redoximorphic concentrations; about 2 percent subrounded mixed rock fragments (2 to 75 millimeters in diameter); common fine prominent reddish brown (5YR 4/4) redoximorphic concentrations; slightly acid.
TYPE LOCATION: Major Land Resource Area (MLRA) 104-Eastern Iowa and Minnesota Till Prairies; Black Hawk County, Iowa subset; about 3.5 miles east of Dunkerton; located about 195 meters (640 feet) south and 774 meters (2,540 feet) east of the northwest corner of section 36, T. 90 N., R. 11 W.; USGS Littleton quadrangle; lat. 42 degrees 34 minutes 4.9 seconds N. and long. 92 degrees 5 minutes 31.5 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Depth to glacial till--50 to 102 centimeters (20 to 40 inches)
Depth to carbonates--102 to more than 203 centimeters (40 to more than 80 inches)
Content of clay in the particle-size control section (weighted average)--8 to 18 percent
Content of sand in the particle-size control section (weighted average)--45 to 85 percent fine sand and sand coarser than fine sand
Special feature--some pedons have a stone line or thin layer, 2 to 13 centimeters (1 to 5 inches) thick of gravelly and sandy materials at the base of the eolian sediments
Ap and A horizon (when present):
Hue--10YR
Value--2 or 3
Chroma--2 or 3
Texture--sandy loam, fine sandy loam, loamy sand, or loamy fine sand
Clay content--5 to 15 percent
Sand content--50 to 90 percent
Reaction--strongly acid to neutral
E (when present) or BE horizon:
Hue--10YR
Value--4 or 5
Chroma--2 to 4
Texture--sandy loam, fine sandy loam, loamy sand, or loamy fine sand
Clay content--5 to 15 percent
Sand content--50 to 90 percent
Reaction--strongly acid to neutral
Bt horizon:
Hue--10YR or 7.5YR
Value--4 to 6
Chroma--2 to 6
Texture--sandy clay loam or sandy loam
Clay content--5 to 18 percent
Sand content--50 to 85 percent
Rock fragment content--1 to 10 percent-a stone line is commonly at the lower boundary of this horizon
Reaction--strongly acid to neutral
2Bt horizon:
Hue--5YR to 2.5Y
Value--4 to 6
Chroma--1 to 8
Texture--loam, sandy clay loam, or clay loam
Clay content--20 to 30 percent
Sand content--30 to 70 percent
Rock fragment content--2 to 12 percent
Reaction--strongly acid to neutral
2BC horizon:
Hue--5YR to 2.5Y
Value--4 to 6
Chroma--1 to 8
Texture--loam, clay loam, sandy clay loam
Clay content--18 to 27 percent, mean of 22 percent
Sand content--35 to 50 percent, mean of 44 percent
Rock fragment content--2 to 12 percent
Reaction--slightly acid to moderately alkaline
Moist bulk density--1.75 to 1.9 gm/cc
COMPETING SERIES: This is the
Oakton series.
Oakton--have a clay content of 14 to 18 percent clay in the particle-size control section and have a sand content of more than 50 percent in the lower third of the series control section
GEOGRAPHIC SETTING:
Parent material--50 to 102 centimeters (20 to 40 inches) of sandy eolian sediments and underlying glacial till
Landform--long convex side slopes and summits on dissected till plains
Slopes--2 to 9 percent
Elevation--198 to 396 meters (650 to 1300 feet) above sea level
Mean annual air temperature--7 to 12 degrees C (45 to 53 degrees F)
Mean annual precipitation--76 to 89 centimeters (30 to 35 inches)
Frost-free period--130 to 186 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Bassett,
Chelsea,
Clyde and
Oran soils.
Bassett--are on similar landscape positions as the Dunkerton soils, have a saturated zone within depths of 1.0 to 1.8 meters (3.25 to 6 feet) in normal years, and have a clay content of 20 to 28 percent in the particle-size control section
Chelsea--are on higher elevations on convex summits of interfluves, side slopes, and crests of escarpments and have a sand content of more than 50 percent in the series control section
Clyde--are at lower elevations in flat to concave drainageways and have a frequently saturated zone within a depth of 0.3 meter (0 to 1 foot) in normal years
Oran--are on similar landscape positions as the Dunkerton soils, have a frequently saturated zone within depths of 0.3 to 0.9 meter (1.0 to 3.0 feet) in normal years, and have a clay content of 18 to 28 percent in the particle-size control section
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--somewhat poorly drained--a frequently saturated zone occurs within depths of 0.3 to 0.9 meter (1.0 to 3.0) feet during April to June in normal years and both perched and apparent saturation can occur on this soil based on the season and intensity of rainfall during a given period of time
Saturated hydraulic conductivity--high in the eolian sediments and low or moderately low in the glacial till
Surface runoff potential--very low or low
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn and soybeans. The native vegetation is big bluestem, little bluestem, switchgrass, other grasses of the tall grass prairie and mixed deciduous trees.
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic section--Dissected till plains
MLRA--Eastern Iowa and Minnesota Till Prairies (104)
LRR M; northeastern Iowa and southeastern Minnesota
Extent--small
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Black Hawk County, Iowa, 2001.
REMARKS:
Particle-size control section--the zone from a depth of 38 to 88 centimeters (15 to 35 inches) (Bt1 and 2Bt2 horizons);
series control section--the zone from the surface to a depth of 150 centimeters (0 to 59 inches) (Ap, BE, Bt1, 2Bt2, 2Bt3, 2BC horizons).
Diagnostic horizons and features recognized in the pedon:
ochric epipedon--the zone from the surface to a depth of 38 centimeters (0 to 15 inches) (Ap and BE horizons);
argillic horizon--the zone from a depth of 38 to 124 centimeters (15 to 49 inches) (Bt1, 2Bt2 and 2Bt3 horizons);
udic moisture regime.
Aquollic subgroup based on low value of zone from the surface to a depth of 38 centimeters (0 to 15 inches) (Ap and BE horizons) and redoximorphic depletions in the zone from a depth of 38 to 64 centimeters (15 to 25 inches) (Bt1 horizon).
Some pedons have vertical seams or wedges of sand or loamy sand about 5 to 15 centimeters (2 to 6 inches) wide and about 0.9 to 1.2 meters (3 to 4 feet) deep extending downward from the stone line into the glacial till.
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.