LOCATION REDBUD ILEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Oxyaquic Hapludalfs
TYPICAL PEDON: Redbud silt loam - gently sloping, on a lacustrine terrace tread, in a cultivated field at an elevation of about 420 feet above sea level. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 9 inches; brown (10YR4/3) silt loam, pale brown (10YR6/3) dry; moderate fine granular structure; friable; common very fine and fine roots throughout; neutral; abrupt smooth boundary. (6 to 10 inches thick)
E--9 to 16 inches; dark yellowish brown (10YR4/4) silt loam, pale brown (10YR6/3) dry; moderate medium platy structure; friable; common very fine roots throughout; few distinct dark brown (10YR 3/3) organic coatings lining root channels; few fine irregular black (N 2.5/) masses of iron-manganese accumulation; slightly acid; abrupt smooth boundary. (0 to 10 inches thick)
Bt1--16 to 22 inches; strong brown (7.5YR5/6) silty clay loam; moderate medium prismatic structure parting to moderate medium subangular blocky; firm; common very fine roots between peds; common distinct brown (7.5YR4/2) clay films on faces of peds; few fine and medium irregular black (7.5YR 2.5/1) masses of iron-manganese accumulation; modereately acid; clear smooth boundary.
Bt2--22 to 28 inches; strong brown (7.5YR5/6) silty clay loam; moderate medium prismatic structure parting to strong medium subangular blocky; firm; few very fine roots between peds; few prominent black (10YR 2/1) iron-manganese stains on faces of peds; common distinct brown (7.5YR 4/2) clay films on faces of peds; common fine and medium irregular black (7.5YR 2.5/1) masses of iron-manganese accumulation; moderately acid; clear smooth boundary.
Bt3--28 to 36 inches; strong brown (7.5YR 5/6) silty clay loam; moderate medium prismatic structure parting to moderate medium subangular blocky; firm; few very fine roots between peds; few prominent black (10YR 2/1) iron-manganese stains on faces of peds; common distinct brown (7.5YR 4/2) clay films on faces of peds; many medium prominent grayish brown (10YR 5/2) iron depletions and common medium distinct yellowish red (5YR 5/6) masses of iron accumulation in the matrix; common fine and medium irregular black (7.5YR 2.5/1) masses of iron-manganese accumulation; moderately acid; clear smooth boundary.
Bt4--36 to 45 inches; strong brown (7.5YR4/4) silty clay loam; moderate medium prismatic structure; friable; few very fine roots between peds; few distinct brown (7.5YR 4/2) clay films on faces of peds; common medium prominent grayish brown (10YR 5/2) iron depletions and common medium prominent yellowish red (5YR 5/6) masses of iron accumulation in the matrix; common fine and medium irregular black (7.5YR 2.5/1) masses of iron-manganese accumulation; moderately acid; abrupt smooth boundary. (Combined thickness of the Bt horizon is 24 to 50 inches.)
2Bt5--45 to 60 inches; dark yellowish brown ( 10YR 4/4) silty clay; moderate medium prismatic structure; very firm; few very fine roots between peds; few distinct dark grayish brown (10YR 4/2) clay films on faces of peds; many medium distinct grayish brown (10YR 5/2) iron depletions and common medium prominent strong brown (7.5YR 5/6) masses of iron accumulation in the matrix; common fine and medium irregular black (7.5YR 2.5/1) masses of iron-manganese accumulation; slightly acid; clear smooth boundary.
2Bt6--60 to 72 inches; dark yellowish brown (10YR 4/4) silty clay loam; moderate medium prismatic structure; firm; few distinct dark grayish brown (10YR 4/2) clay films on faces of peds; many medium distinct grayish brown (10YR 5/2) iron depletions and common medium prominent strong brown (7.5YR 5/6) masses of iron accumulation in the matrix; common fine and medium irregular black (7.5YR 2.5/1) masses of iron-manganese accumulation; slightly acid; clear smooth boundary. (Combined thickness of the 2Bt horizon is 24 to 48 inches.)
2BCt--72 to 80 inches; brown (10YR 4/3) silt loam; weak medium prismatic structure; friable; few distinct dark gray (10YR 4/1) clay films in root channels and pores; common coarse faint grayish brown (10YR 5/2) iron depletions in the matrix; few fine irregular black (7.5YR 2.5/1) masses of iron-manganese accumulation; neutral.
TYPE LOCATION: St. Clair County, Illinois; about 6 miles south of New Athens; approximately 1,280 feet north and 2,040 feet east of the southwest corner of sec. 28, T. 3 S., R. 7W.; USGS RES BUD, ILL. topographic quadrangle; lat. 38 degrees 14 minutes 10 seconds N. and long. 89 degrees 53 minutes 05 seconds W.
RANGE IN CHARACTERISTICS: Depth to the base of the argillic horizon is 54 to more than 80 inches. Loess thickness typically is 36 inches to 70 inches. The particle-size control section averages 27 to 35 percent clay and contains less than 7 percent sand. Carbonates, where present, are below a depth of 4 feet.
The upper part of the control section (Ap) has hue of 10YR, value of 4 or 5 (6 or 7 dry), and chroma of 2 or 3. Some undisturbed pedons have a thin A horizon with a color value of 3 and chroma of 1 or 2. Clay content is 12 to 25 percent and sand content is less than 7 percent. Reaction is strongly acid to neutral, depending on the liming history.
The second part of the control section (E) has hue of 10YR, value of 4 to 6 (6 to 8 dry), and chroma of 3 to 6. It is silt loam or silty clay loam. Clay content is 12 to 32 percent and sand content is less than 7 percent. Reaction is strongly acid to slightly acid when not limed. Pedons that have been limed range to neutral.
Some pedons have a BE or and EB horizon.
The third part of the control section (Bt) has hue of 7.5YR, 10YR or 2.5Y; value of 4 to 6; and chroma of 2 to 6. It is silty clay loam or silt loam. Clay content is 22 to 35 percent. Reaction is very strongly acid to slightly acid.
The lower part of the control section (2Bt, and 2BC or 2C, where present) has hue of 7.5YR, 10YR, 2.5Y, or 5Y; value of 4 to 7; chroma of 2 to 4. It is clay, silty clay, silty clay loam, or silt loam, and can be stratified with these textures. Clay content ranges from 24 to 55 percent, and at least some part has more than 35 percent. Sand content is less than 15 percent. Commonly, pedons contain pressure faces or slickensides. Reaction is very strongly acid to moderately alkaline. Calcium carbonate equivalent ranges from 0 to 5 percent.
COMPETING SERIES: These are the Ashburn(T), Birkbeck, Downsouth(T), Elco, Eleroy, Epley, Gallipolis, Grays, Homen (T), Iona, Middletown, Percell (T), Rend (T), Richview, Rocheport (T), Rockfield, Rozetta, St. Clarles, Stonehead, Sylvan, Throckmorton, Weddel(T), Westgate, Winfield, Wingate, and Wrengart series.
Ashburn soils have a lithic contact at 20 to 40 inches. Birkbeck, Elco, Middletown, Rockfield, St. Clarles, and Throckmorton soils contain more than 7 percent sand in the lower part of the series control section. Downsouth, Richview and Wingate soils have a surface layer that meets all the requirements for a mollic epipedon, except for thickness. Eleroy, Rocheport, Stonehead, and Westgate soils have a paralithic contact in the series control section. Epley, Iona, and Sylvan soils have the depth to the base of soil development at less than 60 inches. Gallipolis, Homen, and Rozetta soils do not have any part of the subsoil that averages more than 35 percent clay. Grays and Wrengart soils have a mean annual soil temperature less than 56 degrees F. Percell soils average more than 7 percent sand in the argillic horizon. Rend, Weddel and Wrengart soils have a brittle layer (Btx horizon) in the lower part of the series control section. Winfield soils do not have any part of the subsoil that has more than 40 percent clay.
GEOGRAPHIC SETTING: Redbud soils are on gently sloping to strongly sloping loess-covered lacustrine terraces treads and risers. Slope ranges from 2 to 18 percent. These soils formed in 36 inches to about 60 inches of loess (Peoria silt) and the underlying lacustrine sediments (Equality Formation). Mean annual temperature is 54 to 57 degrees F., mean annual precipitation is 36 to 40 inches, frost-free period is 170 to 200 days, and elevation is 340 to 430 feet above sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bartelso, Floraville, Lakaskia, Millstadt, and Wabash soils.
The somewhat poorly drained Bartelso and Millstadt soils are on nearly level or gently sloping convex treads of lacustrine terraces. Also, Bartelso soils have a mollic epipedon. The poorly drained Floraville and Lakaskia soils are on nearly level or slightly depressional treads of lacustrine terraces. Also, the Lakaskia soils have a mollic epipedon. The poorly drained Floraville soils and the somewhat poorly drained Millstadt soils form a hydrosequence with the Redbud soils. The very poorly drained Wabash soils have a mollic epipedon and are in drainageways on lacustrine terraces.
DRAINAGE AND PERMEABILITY: Moderately well drained. Permeability is slow. Surface runoff is slow to rapid. Depth to an intermittent perched high water table is 2.0 to 3.5 feet from January to April in most years.
USE AND VEGETATION: Most areas are cropped to corn, soybeans, and small grain. A few areas are pastured or wooded. Native vegetation is mixed hardwood forest.
DISTRIBUTION AND EXTENT: Southwestern and southern Illinois. Extent is moderate, and mainly in MLRA(s) 113 and 114.
MLRA OFFICE RESPONSIBLE: Indianapolis, Indiana
SERIES PROPOSED: St. Clair County, Illinois, 1995. The Redbud series is named for a town in Randolph County.
REMARKS: Redbud soils were formerly included with the terrace variants of the Muren and Alford series.
Diagnostic horizons and features recognized in this pedon are: Ochric epipedon - the zone from the surface to a depth of 16 inches (Ap and E horizons). Argillic horizon - the zone from approximately 16 to 72 inches (Bt1, Bt2, Bt3, Bt4, 2Bt5, and 2Bt6 horizons). Redoximorphic iron depletions - the zone from approximately 28 to 80 inches (Bt3, Bt4, 2Bt5, 2Bt6, and 2BCt horizons).
ADDITIONAL DATA: See data from the St. Clair County Glacial Lake Kaskaskia Study, Part II (S93IL-163-016; NSSL pedon number: 94P-274-1731-1742).