LOCATION BUNKUM IL

Established Series
Rev. RAL-TJE
03/2015

BUNKUM SERIES

The Bunkum series consists of very deep, somewhat poorly drained soils on dissected till plains. They formed in loess, or in loess and the underlying silty water-worked sediments (pedisediment). Slope ranges from 2 to 18 percent. Mean annual precipitation is about 965 mm (38 inches), and mean annual temperature is about 13 degrees C (55 degrees F).

TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Aquic Hapludalfs

TYPICAL PEDON: Bunkum silty clay loam, on a severely eroded, west-facing backslope with a gradient of 9 percent in a cultivated field at an elevation of about 156 meters (510 feet) above mean sea level. (Colors are for moist soil unless otherwise stated.)

Ap--0 to 20 cm (0 to 8 inches); mixed brown (10YR 4/3) and yellowish brown (10YR 5/4) silty clay loam, pale brown (10YR 6/3) dry; moderate very fine subangular blocky structure; friable; many very fine roots; common fine and medium constricted tubular pores; common fine spherical black (7.5YR 2.5/1) iron-manganese nodules with sharp boundaries; about 30 percent clay; neutral; abrupt smooth boundary. [8 to 23 cm (3 to 9 inches) thick]

Bt1--20 to 41 cm (8 to 16 inches); yellowish brown (10YR 5/4) silty clay loam; moderate fine and medium subangular blocky structure; firm; common very fine roots; few fine constricted tubular pores; common distinct brown (10YR 5/3) clay films on faces of peds; few fine distinct light brownish gray (10YR 6/2) iron depletions; common fine distinct yellowish brown (10YR 5/6) masses of oxidized iron in the matrix; common fine and medium spherical black (7.5YR 2.5/1) iron-manganese nodules with sharp boundaries; about 34 percent clay; slightly acid; clear smooth boundary.

Bt2--41 to 66 cm (16 to 26 inches); yellowish brown (10YR 5/4) silty clay loam; weak fine prismatic structure parting to weak fine and medium subangular blocky; firm; common very fine roots; few very fine constricted tubular pores; common distinct brown (10YR 4/3) clay films on faces of peds; common fine distinct light brownish gray (10YR 6/2) iron depletions; common fine and medium distinct strong brown (7.5YR 5/6) masses of oxidized iron in the matrix; common medium and coarse irregular black (7.5YR 2.5/1) iron-manganese masses with clear strong brown (7.5YR 4/6) boundaries; about 31 percent clay; slightly acid; clear smooth boundary.

Btg1--66 to 81 cm (26 to 32 inches); grayish brown (2.5Y 5/2) silty clay loam; weak medium prismatic structure parting to weak medium angular blocky; firm; few very fine roots; few fine and medium constricted tubular pores; common distinct dark grayish brown (10YR 4/2) clay films on faces of peds; few fine distinct light olive brown (2.5Y 5/4) and common medium prominent strong brown (7.5YR 5/6) masses of oxidized iron in the matrix; few medium and coarse irregular black (7.5YR 2.5/1) iron-manganese masses with clear strong brown (7.5YR 4/6) boundaries; about 28 percent clay; moderately acid; clear smooth boundary.

Btg2--81 to 102 cm (32 to 40 inches; light brownish gray (2.5Y 6/2) silt loam; weak coarse angular blocky structure; friable; few very fine roots; few fine and medium constricted tubular pores; few prominent dark grayish brown (10YR 4/2) clay films on vertical faces of peds; common medium and coarse prominent strong brown (7.5YR 5/6) masses of oxidized iron in the matrix; few medium irregular black (7.5YR 2.5/1) iron-manganese masses with clear strong brown (7.5YR 4/6) boundaries; about 26 percent clay; moderately acid; gradual smooth boundary. [Combined thickness of the Bt horizon is 69 to 132 cm (27 to 52 inches).]

CBg--102 to 147 cm (40 to 58 inches); light brownish gray (2.5Y 6/2) silt loam; massive; friable; few very fine roots; few fine and medium constricted tubular pores; few medium and coarse prominent strong brown (7.5YR 5/6) masses of oxidized iron in the matrix; few fine and medium irregular black (7.5YR 2.5/1) iron-manganese masses with diffuse strong brown (7.5YR 4/6) boundaries; about 21 percent clay; slightly acid; abrupt smooth boundary. [0 to 61 cm (0 to 24 inches) thick]

2CB--147 to 200 cm (58 to 79 inches); brown (7.5YR 5/4) silt loam; massive; friable; few fine and medium constricted tubular pores; few fine distinct pinkish gray (7.5YR 6/2) iron depletions; few medium spherical very dark brown (7.5YR 2.5/3) iron-manganese concretions with clear strong brown (7.5YR 4/6) boundaries; about 25 percent clay and 8 percent sand; slightly acid.

TYPE LOCATION: St. Clair County, Illinois; about 1 mile west of Smithton; approximately 1,740 feet south and 160 feet east of the center of sec. 29, T. 1 S., R. 8 W.; USGS Millstadt, Ill. topographic quadrangle; lat. 38 degrees 24 minutes 47 seconds N. and long. 90 degrees 00 minutes 37 seconds W., NAD 27.

RANGE IN CHARACTERISTICS:
Depth to the base of the argillic horizon: 61 to 152 cm (24 to 60 inches)
Thickness of the loess: 61 to 152 cm (24 to 60 inches)
Particle-size control section: averages 25 to 35 percent clay and less than 7 percent sand; typically about one-third to one-half of the sand is very fine

Ap, A, and E horizons:
Hue: 10YR
Value: 4 or 5 (6 or 7 dry)
Chroma: 2 to 4
Texture: silt loam or silty clay loam
Clay content: 18 to 35 percent
Sand content: less than 7 percent
Reaction: strongly acid to slightly acid except in pedons that have been limed range to neutral

In most eroded pedons the E horizon has been mixed into the Ap horizon.

Bt horizon and upper part of Btg horizon:
Hue: 10YR or 2.5Y
Value: 4 to 6
Chroma: 2 to 4

Btg horizon, middle and lower parts:
Hue: 10YR, 2.5Y, or less commonly 5Y
Value: of 4 to 6
Chroma: 1 or 2
Texture: silty clay loam or silt loam
Clay content: 25 to 35 percent
Reaction: very strongly acid to moderately acid in the upper part and strongly acid to slightly acid in the lower part

BCg or CBg horizon:
Hue: 10YR to 5Y
Value: 4 to 6
Chroma: 1 to 4
Texture: silt loam
Clay content: 18 to 27 percent
Sand content: less than 7 percent
Reaction: strongly acid to neutral

2CB horizon, and 2C horizon, where present:
Hue: 7.5YR to 5Y
Value: 4 to 6
Chroma: 1 to 4
Texture: commonly silt loam, or less commonly, silty clay loam, loam or clay loam
Clay content: 15 to 30 percent
Sand content: 5 to 30 percent; averages more than 7 percent
Reaction: strongly acid to neutral

COMPETING SERIES: These are the Appleriver, Blair, Fishhook, Freeburg, Geff, Glenford, Keene, Muren, Reesville, Sugarvalley, Torox, and Xenia series. Appleriver soils have a paralithic contact between a depth of 102 to 152 cm (40 and 60 inches). Blair soils average more than 5 percent fine sand or coarser sand in the particle-size control section. Fishhook soils average more than 30 percent clay in the lower part of the series control section. Freeburg soils contain more than 7 percent sand in the upper part of the series control section. Geff soils average more than 7 percent sand the lower part of the series control section. Glenford and Keen soils have a mean annual soil temperature of less than 13 degrees C (56 degrees F). Muren soils average less than 7 percent sand in the lower part of the series control section. Reesville, Sugarvalley, Torox, and Xenia soils contain carbonates within a depth of 152 cm (60 inches).

GEOGRAPHIC SETTING: Bunkum soils are on dissected till plains of Illinoian age. Slope ranges from 2 to 18 percent. These soils formed in loess or in loess and the underlying silty water-worked sediments (pedisediment) overlying a paleosol. Mean annual air temperature is 12 to 14 degrees C (54 to 57 degrees F). Mean annual soil temperature is 13 to 15 degrees C (56 to 59 degrees F). Mean annual precipitation is 914 to 1016 mm (36 to 40 inches). Frost-free period is 170 to 200 days. Elevation is 107 to 244 meters (350 to 800 feet) above sea level.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Atlas, Darmstadt, Grantfork, Homen, Marine, Ruma, and Ursa soils. The somewhat poorly drained Atlas and Grantfork soils and well drained Ursa soils formed in till that contains a strongly developed paleosol and are on backslopes and footslopes downslope from the Bunkum soils. Also, the Grantfork soils contain a concentration of exchangeable sodium in the subsoil. The somewhat poorly drained Coulterville soils are on summits and in upland drainageways nearby and contain a concentration of exchangeable sodium in the subsoil. The somewhat poorly drained Darmstadt and Marine soils are on summits above the Bunkum soils. Darmstadt soils have a natric horizon. The fine-textured Marine soils have an abrupt textural change. The moderately well drained Homen and well drained Ruma soils are on summits, shoulders, and backslopes above the Bunkum soils.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Somewhat poorly drained. In drained areas, depth to the top of an intermittent apparent high water table ranges from 30 to 61 cm (1.0 to 2 feet) from December to April in normal years. The potential for surface runoff is medium or high. Saturated hydraulic conductivity is moderately high. Permeability is moderately slow.

USE AND VEGETATION: Most areas are cultivated. Corn, soybeans, milo, and small grain are the principal crops. More sloping areas are in forages for hay or pasture, or in woodland. Native vegetation is deciduous forest.

DISTRIBUTION AND EXTENT: MLRA 114B in southwestern Illinois. The series is of moderate extent.

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

SERIES ESTABLISHED: St. Clair County, Illinois, 1997.

REMARKS: Bunkum soils formerly were included with variants of Alford and Muren series. The Bunkum series was named for Bunkum Road in St. Clair County.

Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: from the surface to a depth of 20 cm (8 inches) (Ap horizon).
Argillic horizon: from a depth of 20 to 102 cm (8 to 40 inches) (Bt1, Bt2, Btg1, and Btg2 horizons).
Aquic conditions - redoximorphic features present throughout the soil such as iron depletions, masses of oxidized iron, iron-manganese nodules, and reduced chroma matrix.

03/2015 revision: updated terminology used to describe redox features; updated competing series; added metric units; converted to semitabular format

ADDITIONAL DATA: For characterization data refer to pedon S93IL163015 from the St. Clair County Glacial Lake Kaskaskia Study, KSSL Pedon No. 94P0273, sampled about a 0.5 mile southeast of typical pedon.

National Cooperative Soil Survey
U.S.A.