LOCATION CLARKSDALE ILEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Udollic Endoaqualfs
TYPICAL PEDON: Clarksdale silt loam, 0 to 2 percent slopes in a cultivated field at an elevation of 198 meters (650 feet) above mean sea level (Colors are for moist soil unless otherwise stated.)
Ap--0 to 20 cm (0 to 8 inches); very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) dry; moderate medium granular structure; friable; common fine roots throughout; neutral; abrupt smooth boundary. [15 to 25 cm (6 to 10 inches) thick]
E--20 to 30 cm (8 to 12 inches); dark grayish brown (10YR 4/2) silt loam; moderate medium platy structure parting to weak very fine subangular blocky; friable; common very fine and fine roots throughout; many faint very dark grayish brown (10YR 3/2) organic coats on faces of peds and in pores; few fine prominent yellowish brown (10YR 5/6) masses of iron accumulation lining root channels and/or pores, few fine distinct black (2.5Y 2/1) masses of iron and manganese accumulation throughout, and many fine distinct light gray (10YR 7/1) and light gray (10YR 7/2) clay depletions between peds; neutral; clear smooth boundary. [7.5 to 20 cm (3 to 8 inches) thick]
BE--30 to 41 cm (12 to 16 inches); grayish brown (10YR 5/2) silt loam; moderate fine subangular blocky structure; friable; few fine roots throughout; common distinct very dark grayish brown (10YR 3/2) organo-clay films on faces of peds and in pores; few fine prominent black (2.5Y 2/1) masses of iron and manganese accumulation throughout, common fine prominent yellowish brown (10YR 5/6) masses of iron accumulation throughout, and common fine faint light gray (10YR 7/1) clay depletions between peds; moderately acid; clear smooth boundary. [0 to 18 cm (0 to 7 inches) thick]
Bt1--41 to 58 cm (16 to 23 inches); brown (10YR 5/3) silty clay loam; moderate medium prismatic structure parting to moderate medium subangular blocky; firm; few very fine and fine roots throughout; many prominent dark grayish brown (10YR 4/2) clay films on faces of peds and many prominent very dark gray (10YR 3/1) organo-clay films on faces of peds and in pores; common fine prominent black (2.5Y 2/1) masses of iron and manganese accumulation and common fine distinct yellowish brown (10YR 5/6) masses of iron accumulation throughout; moderately acid; clear smooth boundary.
Bt2--58 to 78 cm (23 to 31 inches); brown (10YR 5/3) silty clay loam; moderate medium prismatic structure parting to moderate medium subangular blocky; firm; few fine roots throughout; many faint grayish brown (10YR 5/2) clay films on faces of peds and many prominent very dark gray (10YR 3/1) organo-clay films on faces of peds and in pores; many fine distinct yellowish brown (10YR 5/6) masses of iron accumulation throughout, few fine prominent strong brown (7.5YR 5/6) masses of iron accumulation throughout, common fine prominent black (2.5Y 2/1) masses of iron and manganese accumulation throughout, and common fine faint light brownish gray (10YR 6/2) iron depletions throughout; moderately acid; gradual wavy boundary. [Combined thickness of the Bt horizon is 13 to 46 cm (5 to 18 inches).]
Btg1--78 to 119 cm (31 to 47 inches); light brownish gray (2.5Y 6/2) silty clay loam; moderate coarse prismatic structure parting to moderate coarse subangular blocky; firm; few fine roots throughout; common prominent grayish brown (10YR 5/2) clay films on faces of peds and many prominent very dark gray (10YR 3/1) organo-clay films on faces of peds and in pores; many fine and medium prominent strong brown (7.5YR 5/6) masses of iron accumulation throughout, few fine prominent black (2.5Y 2/1) masses of iron and manganese accumulation throughout, and few fine faint light brownish gray (10YR 6/2) iron depletions lining root channels and/or pores; neutral; gradual wavy boundary.
Btg2--119 to 145 cm (47 to 57 inches); light brownish gray (2.5Y 6/2) silt loam; weak coarse prismatic structure; firm; few fine roots throughout; common prominent dark grayish brown (10YR 4/2) clay films in root channels and/or pores; many medium prominent strong brown (7.5YR 5/6) masses of iron accumulation and few fine prominent black (2.5Y 2/1) masses of iron and manganese accumulation throughout; neutral; clear wavy boundary. [Combined thickness of the Btg horizon is 51 to 102 cm (20 to 40 inches).]
BCg--145 to 170 cm (57 to 67 inches); light brownish gray (2.5Y 6/2) silt loam; weak coarse subangular blocky structure; firm; common prominent dark grayish brown (10YR 4/2) clay films in root channels and/or pores; common medium prominent strong brown (7.5YR 5/6) masses of iron accumulation and common medium prominent yellowish red (5YR 5/6) masses of iron accumulation throughout; neutral; clear wavy boundary. [0 to 38 cm (0 to 15 inches) thick]
Cg--170 to 203 cm (67 to 80 inches); light brownish gray (10YR 6/2) silt loam; massive; friable; few distinct dark grayish brown (10YR 4/2) clay films in root channels and/or pores; many medium prominent yellowish red (5YR 4/6) masses of iron accumulation and common medium prominent strong brown (7.5YR 5/6) masses of iron accumulation throughout; neutral.
TYPE LOCATION: Adams County, Illinois, 800 feet south and 550 feet east of the northwest corner of sec. 16, T. 2 N., R. 7 W.; USGS Lorraine, IL. topographic quadrangle; lat. 40 degrees 9 minutes 55.1 seconds N. and long. 91 degrees 13 minutes 18 seconds W. NAD 27.
RANGE IN CHARACTERISTICS: The depth to the base of the argillic horizon ranges from 102 to 152 cm (40 to 60 inches). The depth to carbonates is greater than 102 cm (40 inches) and commonly greater than 152 cm (60 inches). The particle-size control section averages 35 to 42 percent clay. Individual subhorizons can have as little as 30 percent clay. The series control section averages less than 8 percent sand and less than 1 percent rock fragments.
The Ap horizon has value of 2 or 3, and chroma of 1 or 2. It is silt loam. Reaction ranges from neutral to moderately acid.
The E horizon has value of 4 to 6, and chroma of 1 or 2. It is silt loam. Reaction is strongly acid to neutral. This horizon is not present in some eroded pedons.
The Bt horizon has hue of 10YR, value of 4 to 6, and chroma of 2 to 6. Redoximorphic iron depletions and concentrations have hue of 7.5YR, 10YR, or 2.5Y, value of 2 to 6 and chroma of 1 to 8. Texture is silty clay loam or silty clay. Reaction is strongly acid to neutral.
The Btg horizon has hue of 10YR, 2.5Y, or 5Y, value of 4 to 6, and chroma of 1 to 4. Redoximorphic iron depletions and concentrations have hue of 7.5YR, 10YR, or 2.5Y, value of 2 to 6 and chroma of 1 to 8. Texture is silty clay loam, silty clay or silt loam. Reaction is slightly acid to moderately alkaline.
The Cg horizon has hue of 10YR, 2.5Y, or 5Y, value of 4 to 6, and chroma of 1 to 6. Redoximorphic iron depletions and concentrations have hue of 5YR, 7.5YR, 10YR, or 2.5Y, value of 2 to 6 and chroma of 1 to 8. Average clay content ranges from 18 to 27 percent. Reaction is typically neutral to moderately alkaline, but is slightly acid in the upper part in some pedons.
COMPETING SERIES: These are the Givin and Oconee soils. Given soils average more than 27 percent clay in the Cg horizon. Oconee soils have a mean annual soil temperature at 51 cm (20 inches) of more than 13.3 degrees C (56 degrees F).
GEOGRAPHIC SETTING: Clarksdale soils are on summits and side slopes on loess-mantled ground moraines. Slope gradients commonly are 0 to 2 percent but range to 7 percent. Clarksdale soils formed in loess. They are in areas on uplands between Typic Hapludalfs on crests and side slopes near drainageways and Argiudolls on ground moraines farther from the drainageways. Climate is midcontinental with hot summers and cold winters. Mean annual air temperature ranges from 10 to 12 degrees C. (50 to 54 degrees F.), mean annual precipitation ranges from 864 to 1016 mm (34 to 40 inches), frost free days range from 160 to 190 days, and elevation ranges from 122 to 305 meters (400 feet to 1000 feet) above sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Downs, Ipava, Keomah, Rozetta, Rushville, and Sable soils. The moderately well drained Downs and Rozetta soils are in similar and more sloping areas. Ipava and Keomah soils are on similar nearby landscapes and form a biosequence with Clarksdale soils. The poorly drained Rushville soils do not have a dark surface layer and are on nearly level or slightly depressional areas. The poorly drained Sable soils have mollic epipedons and are typically on broad upland areas farther from the dissecting drainageways than Clarksdale soils.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Somewhat poorly drained. The potential for surface runoff is low to medium. Saturated hydraulic conductivity is 1.41 to 4.23 micrometers per second in the most restrictive layers. Permeability is moderately slow. In undisturbed areas, the seasonal high water table is above a depth of 51 cm (20 inches) for some time in normal years. Where artificially drained it is above a depth of 91 cm (36 inches) for short periods in spring in normal years.
USE AND VEGETATION: Most areas of Clarksdale soils are used to grow corn, soybeans, small grain, and hay. Natural vegetation is grass and deciduous hardwood forest.
DISTRIBUTION AND EXTENT: Central and western Illinois mainly in MLRA 108B and 115C. Clarksdale soils are extensive (more than 103,000 acres correlated).
MLRA OFFICE RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Christian County, Illinois, 1946.
REMARKS: The typical pedon was moved from Christian County, Illinois to Adams County, Illinois with the 10/2001 update. The Christian County pedon was in an area where the glacial till is shallower than is typical for the Clarksdale soils.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to a depth of 41 cm (16 inches) - (Ap E, and BE horizons);
Argillic horizon - the zone from 41 to 145 cm (16 inches to 57 inches) - (Bt1, Bt2, Btg1, and Btg2 horizons);