LOCATION KILLDUFF                IA

Established Series
Rev. LMN-JRW-RJK
08/2015

KILLDUFF SERIES

The Killduff series consists of deep, well and moderately well drained, moderately permeable soils formed in loess on hillslopes of dissected till plains. Slope ranges from 2 to 18 percent. Mean annual temperature is about 9.4 degrees C(49 degrees F), and mean annual precipitation is about 940 mm (37 inches).

TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Dystric Eutrudepts

TYPICAL PEDON: Killduff silty clay loam on a convex 6 percent east-facing slope - cultivated. (Colors are for moist soil unless otherwise stated.)

Ap--0 to 18 centimeters (0 to 7 inches); black (10YR 2/1) silty clay loam, very dark grayish brown (10YR 3/2) dry; weak medium subangular blocky and weak fine granular structure; friable; neutral; abrupt smooth boundary.

A--18 to 23 centimeters (7 to 9 inches); very dark brown (10YR 2/2) silty clay loam, dark grayish brown (10YR 4/2) dry; moderate very fine subangular blocky and moderate fine granular structure; friable; slightly acid; gradual smooth boundary. [Combined thickness of A horizon is 15 to 30 centimeters (6 to 12 inches).]

BA--23 to 36 centimeters (9 to 14 inches); brown (10YR 4/3) silty clay loam, coatings on faces of peds are dark brown (10YR 3/3) and very dark grayish brown (10YR 3/2), brown (10YR 4/3) crushed; moderate very fine subangular blocky and moderate fine granular structure; friable; slightly acid; gradual smooth boundary. [0 to 15 centimeters (0 to 6 inches) thick]

Bw1--36 to 51 centimeters (14 to 20 inches); brown (10YR 4/3) silty clay loam, coatings on faces of a few peds are dark brown (10YR 3/3); moderate very fine subangular blocky structure; friable; few thin discontinuous very dark grayish brown (10YR 3/2) clay films on faces of peds; slightly acid; gradual smooth boundary.

Bw2--51 to 64 centimeters (20 to 25 inches); brown (10YR 4/3) silty clay loam; few fine distinct grayish brown (2.5Y 5/2) mottles and few fine faint yellowish brown (10YR 5/6) mottles; weak very fine subangular blocky structure; friable; few thin discontinuous dark brown (10YR 3/3) clay films on faces of peds; few dark accumulations (iron maganese); slightly acid; gradual smooth boundary.

Bw3--64 to 89 centimeters (25 to 35 inches); dark yellowish brown (10YR 4/4) silty clay loam; many fine distinct grayish brown (2.5Y 5/2) and common fine distinct strong brown (7.5YR 5/6) mottles; weak fine and very fine subangular blocky structure; friable; few fine dark accumulations (iron maganese); slightly acid; gradual smooth boundary. [Combined thickness of the BW horizon is 43 to 64 centimeters (17 to 25 inches).]

BC--89 to 117 centimeters (35 to 46 inches); mottled grayish brown (2.5Y 5/2) and yellowish brown (10YR 5/4) silt loam; many fine distinct strong brown (7.5YR 5/6) mottles; weak medium prismatic structure parting to weak medium subangular blocky; friable; few fine dark accumulations (iron maganese); slightly acid; gradual smooth boundary. [18 to 30 centimeters (7 to 12 inches) thick]

C--117 to 152 centimeters (46 to 60 inches); mottled grayish brown (2.5Y 5/2) and yellowish brown (10YR 5/4) silt loam; many fine distinct strong brown (7.5YR 5/6) mottles; massive with some vertical cleavage; friable; few fine dark accumulations (iron maganese); neutral.

TYPE LOCATION: Poweshiek County, Iowa; about 4 miles east and 4 miles north of Grinnell; 2,015 feet east and 160 feet south of the northwest corner, sec. 30, T. 81 N., R. 15 W.

RANGE IN CHARACTERISTICS:
Thickness of the mollic epipedon-less than 25 centimeters
Depth to carbonates-- more than 100 centimeters
Clay content of the particle-size control section (weighted average)--27 to 35 percent
Sand content of the particle-size control section (weighted average)--less than 8 percent
Rock fragment content--0 percent

A or Ap horizon:
Hue--10YR
Value--2 or 3
Chroma--1 or 2
Texture--silty clay loam
Clay content--27 to 33 percent
Sand content--less than 8 percent
Reaction--pH 6.1 to 7.3 (slightly acid to neutral)
Thickness-less than 25 centimeters

AB or BA horizon (when present):
Hue--10YR
Value--3 or 4
Chroma--2 or 3
Texture--silty clay loam
Clay content--27 to 33 percent
Sand content--less than 8 percent
Reaction-- pH 6.1 to 7.3 (slightly acid to neutral)
Thickness--0 to 15 centimeters

Bw horizon:
Hue--10YR, 2.5Y or 5Y
Value--4 or 5
Chroma--3 or 4
Texture--silty clay loam or silt loam
Clay content--25 to 35 percent
Sand content--less than 8 percent
Reaction--pH 5.6 to 7.3 (moderately acid to neutral)
Thickness--43 to 64 centimeters

Note: Redox features with hue of 10YR, 2.5Y or 5Y; value of 5 or 6; and chroma of 2 increase with depth. The percentage of redox features with chroma of 2 ranges from 20 to 40 percent of the matrix with depths ranging from 60 to 75 centimeters (24 to 30 inches).

BC horizon (when present):
Hue-2.5Y or 10YR
Value--4 to 6
Chroma-2 to 4
Texture--silt loam or silty clay loam
Clay content--23 to 31 percent
Sand content--less than 8 percent
Reaction-- pH 6.1 to 7.3 (slightly acid to neutral)

Note: In many pedons, the matrix is about equal parts of brown and grayish colors.

C horizon (when present):
Hue--10YR, 2.5Y or 5Y
Value-5 or 6
Chroma--1 to 4
Texture--silt loam or silty clay loam
Clay content--20 to 30 percent
Sand content--less than 8 percent
Reaction-- pH 6.1 to 7.3 (slightly acid to neutral)

The gray colors are relic features that are related stratigraphically to a deoxidized weathering zone. The depth to maximum percent clay, depth to free carbonates, and depth to relict gray colors decrease with increasing percent gradient on convex slopes.

COMPETING SERIES: These are the Contrary, Drury, and Exette series of the same family and the Downs, Exira, Hedrick, Ladoga, Mt. Carroll, Nira, Port Byron, Seaton, and Tama series.
Contrary: have a lower maximum clay content and a lower average clay content in the control section.
Drury: have lighter colored A horizons, have less clay in the A and B horizons, and lack 20 percent grayish mottles in any part of the B horizon.
Exette: have less clay in the B horizons.
Downs: have argillic horizons and lack grayish mottles above 76 centimeters (30 inches)
Exira: have mollic epipedons
Hedrick: have argillic horizons and have dominantly gray matrix colors at shallower depths
Ladoga: have argillic horizons and lack grayish mottles above 76 centimeters (30 inches)
Mt. Carroll: have argillic horizons and lack grayish mottles above 76 centimeters (30 inches)
Nira: have mollic epipedons and have gray deoxidized matrix colors at a shallower depth
Port Byron: have mollic epipedons, argillic horizons and lack grayish mottles above 76 centimeters (30 inches), have somewhat less clay in the B horizon and are deeper to grayish mottles.
Seaton: have argillic horizons and lack grayish mottles above 76 centimeters (30 inches)
Tama: have mollic epipedons, argillic horizons and lack grayish mottles above 76 centimeters (30 inches)

GEOGRAPHIC SETTING:
Parent material--loess
Landform--hillslopes on dissected till plains
Slope-2 to 18 percent
Elevation--170 to 339 meters (669 to 1335 feet) above sea level
Mean annual air temperature-8.5 to 10.3 degrees C (47 to 51 degrees F)
Mean annual precipitation--883 to 993 millimeters (35 to 39 inches)
Frost-free period--170 to 205 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Tama soils, which are upslope.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--well and moderately well drained --a frequently saturated zone does not occur within a depth of 1.8 meters during the wettest periods of years when precipitation is within one standard deviation of 30 year mean of annual precipitation
Saturated hydraulic conductivity--1.00 to 10.00 micrometers per second (moderately high)
The grayish colors are inherited from a geological weathering zone and are not a reflection of the present drainage. Permeability is moderate. Surface runoff is medium.

USE AND VEGETATION: Used mainly for cultivated crops with some hay or pasture in rotation. Native vegetation was tall prairie grasses.

DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic sections--Dissected till plains, Till plains
MLRAs--Illinois and Iowa Deep Loess and Drift (108)
LRR M; Iowa, Illinois, Minnesota and Wisconsin
Extent--moderate

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana

SERIES ESTABLISHED: Jasper County, Iowa, 1975.

REMARKS:
Killduff soils are on short, convex to straight side slopes, coves at the head of drainageways, and in a few places, the tops of lowered interfluves in uplands. These soils formed in a deoxidized and leached or a thin, mottled, oxidized and leached over a deoxidized and leached weathering zone in Wisconsinan Age loess. The loess is 4 to 15 feet thick and is underlain by pre-Wisconsin glacial till.
Clay films are noticeable, but the increase in clay from the A to the B horizons fails to meet the 1.2 required for an argillic horizon. The gray colors were not used in the classification of this soil, as they are considered to be inherited from a relict deoxidized and leached weathering zone.

Diagnostic horizons and features recognized in this pedon are:
ochric epipedon - the zone from the surface to a depth of 23 centimeters (9 inches Ap and A horizons);
cambic horizon - the zone from 23 to 117 centimeters (9 to 46 inches (BA, Bw1, Bw2, Bw3, and BC horizons).

Taxonomy version--Keys to Soil Taxonomy, twelfth edition, 2014

Additional Data:
Pedon data from soil characterization lab at Iowa State University and the KSSL was evaluated in July 2015 in revising the Range in Characteristics.
NASIS Pedon ID#--1981IA157005

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National Cooperative Soil Survey
U.S.A.