LOCATION HARRISON ILEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Oxyaquic Argiudolls
TYPICAL PEDON: Harrison silt loam - on a convex slope of 3 percent in a cultivated field at an elevation of 665 feet. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 10 inches; very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) dry; weak fine granular structure; friable; common very fine and few fine roots; slightly acid; abrupt smooth boundary. (7 to 12 inches thick)
BA--10 to 14 inches; brown (10YR 4/3) silt loam; weak very fine and fine subangular blocky structure; friable; few very fine roots; many distinct very dark grayish brown (10YR 3/2) organic coatings on faces of peds; moderately acid; clear smooth boundary. (0 to 6 inches thick)
Bt1--14 to 20 inches; brown (10YR 4/3) silt loam; moderate fine subangular blocky structure; friable; few very fine roots; common distinct very dark grayish brown (10YR 3/2) and few distinct very dark gray (10YR 3/1) organo-clay films on faces of peds; few fine faint dark yellowish brown (10YR 4/4) masses of iron accumulation along micropores; few fine manganese accumulations in the matrix; moderately acid; clear smooth boundary.
Bt2--20 to 27 inches; brown (10YR 4/3) silty clay loam; weak fine prismatic structure parting to moderate medium subangular blocky; firm; few very fine roots; common distinct very dark grayish brown (10YR 3/2) organo-clay films on faces of peds; few fine faint brown (7.5YR 4/4), brown (10YR 5/3) and dark yellowish brown (10YR 4/4) masses of iron accumulation along micropores; few fine manganese accumulations in the matrix; moderately acid; clear smooth boundary.
Bt3--27 to 35 inches; brown (10YR 5/3) silty clay loam; moderate medium subangular blocky structure; firm, few very fine roots; few distinct dark grayish brown (10YR 4/2) clay films on faces of peds; many fine faint dark yellowish brown (10YR 4/4) and few fine faint brown (7.5YR 4/4) masses of iron accumulation along micropores; few fine manganese accumulations in the matrix; moderately acid; clear smooth boundary.
Bt4--35 to 45 inches; yellowish brown (10YR 5/4) silt loam; weak medium and coarse subangular blocky structure; firm; few very fine roots; few distinct dark grayish brown (10YR 4/2) clay films on faces of peds; many fine distinct grayish brown (10YR 5/2) iron depletions along micropores; common fine faint dark yellowish brown (10YR 4/4) and few fine faint brown (7.5YR 4/4) masses of iron accumulation in the matrix; few fine manganese accumulations in the matrix; moderately acid; clear smooth boundary. (Combined thickness of the Bt horizons is 22 to 46 inches.)
2Btg--45 to 65 inches; grayish brown (10YR 5/2) silty clay loam; weak medium and coarse subangular blocky structure; firm; few distinct gray (10YR 5/1) clay films on faces of peds; few fine faint brown (10YR 5/3), common fine and medium distinct dark yellowish brown (10YR 4/4), and few fine distinct brown (7.5YR 4/4) masses of iron accumulation in the matrix; few fine manganese accumulations in the matrix; about 15 percent sand; about 1 percent gravel; slightly acid; abrupt smooth boundary. (7 to 24 inches thick)
3Btgb--65 to 80 inches; grayish brown (2.5Y 5/2) clay loam; moderate coarse subangular blocky structure; firm; common distinct olive gray (5Y 4/2) clay films on faces of peds; common medium distinct yellowish brown (10YR 5/4) masses of iron accumulation in the matrix; few fine manganese accumulations in the matrix; about 5 percent gravel; neutral.
TYPE LOCATION: Christian County, Illinois; about 6 miles south and 2 1/4 miles east of Taylorville; 228 feet north and 1350 feet west of the southeast corner of sec. 24, T. 12 N., R. 2 W.; USGS Clarksdale, IL. Topographic quadrangle; lat. 39 degrees 27 minutes 59 seconds N. and long. 089 degrees 15 minutes 17 seconds W.; NAD 27.
RANGE IN CHARACTERISTICS: The depth to the base of the argillic ranges from 45 to 70 inches in thickness. The loess is 40 to 60 inches in thickness. The particle-size control section averages between 27 and 35 percent clay and less than 5 percent sand. Redox depletions with chroma of 2 or less are not present in the 6 inches immediately below the mollic epipedon. Carbonates are not present at depths less than 60 inches.
The Ap and A horizons have hue of 10YR, value of 2 or 3 (4 or 5 dry), and chroma typically of 1 or 2, but some pedons have chroma of 3. Reaction is neutral or slightly acid. In some pedons, an A horizon beneath the Ap horizon is as much as 8 inches in thickness.
The AB or BA horizons, where present, has hue of 10YR, value of 3 or 4 (4 through 6 dry), and chroma of 2 through 4. It is silt loam or silty clay loam.
The Bt horizons have hue of 10YR, value of 4 through 6, and chroma typically of 3 or 4 but including 2 through 6 in individual subhorizons. Redox features have hue of 10YR, 7.5YR, or 5YR; value of 4 through 6; and chroma of 2 through 8. The Bt horizon is dominantly silty clay loam, but has`subhorizons of silt loam. It is strongly acid to slightly acid.
The 2Bt or 2BC horizons have hue of 10YR or 7.5YR, and less commonly 2.5Y; value of 4 through 6; and chroma of 2 through 6. Redox features have hue of 7.5YR, 10YR, 2.5Y, or 5Y; value of 4 through 6; and chroma of 2 through 8. The 2Bt or 2BC horizon is silty clay loam, silt loam, loam, or clay loam. It contains more sand than the overlying loess, and typically contains some pebbles. Reaction is moderately acid to neutral. Some pedons have a 2C horizon within a depth of 60 inches, but most pedons have a buried soil (paleosol) beneath the 2Bt or 2BC horizon within a depth of 70 inches.
The 3Btgb horizon has hue of 10YR, 2.5Y or 5Y, or is neutral, value of 4 through 6, and chroma of 0 through 3 and is mottled. It typically is clay loam or clay, but is silty clay or silty clay loam in some pedons. Reaction is slightly alkaline to strongly acid.
COMPETING SERIES: These are the Assumption, Aviston, Barrington, Blackberry, Catlin, Clare, Dana, Danabrook, Geryune, Graymont, Keltner, Saybrook, and Totanang series. Assumption and Clare soils have more than 15 percent sand in some horizon above a depth of 40 inches. Aviston soils formed in more than 60 inches of loess and have less than 15 percent sand in the lower part of the series control section. Barrington, Catlin, Dana, Danabrook, Geryune, Graymont, and Saybrook soils have carbonates at depths of less than 60 inches. Blackberry soils average less than 30 percent clay in the lower part of the series control section. Keltner soils have a paralithic contact at depths of 40 to 60 inches. Totanang soils have more than 15 percent rock fragments in the lower part of the series control section.
GEOGRAPHIC SETTING: Harrison soils are on the crests and upper side slopes of convex ridges and broad interstream divides on the Illinoian till plain. Slope gradients range from 0 to 10 percent. These soils formed in 40 to 60 inches of Wisconsinan loess and the underlying coarser textured Roxana silt or loamy materials. These materials contain more sand than the overlying loess. They are underlain at depths generally between 60 and 70 inches by Illinoian till that contains a strongly developed paleosol. Mean annual temperature varies from 52 to 57 degrees F., and mean annual precipitation varies from 35 to 40 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cowden, Darmstadt, Douglas, Herrick, Piasa, Tamalco, Velma, and Virden soils. Cowden, Piasa, and Virden soils are poorly drained, have a fine textured control section, and are on nearly level parts of the loess covered till plains nearby at either higher or lower elevations. In addition, the Piasa soils have a natric horizon. The somewhat poorly drained Darmstadt and the moderately well drained Tamalco soils are on similar parts of the landscape nearby or on side slopes along drainageways and have a natric horizon. The well drained Douglas soils are on slightly higher positions in the landscape. The somewhat poorly drained Herrick soils are nearby on convex ridges or interstream divides with low relief and are either at higher or lower elevations. The well drained Velma soils contain more than 15 percent fine sand or coarser in the control section and are down slope from Harrison soils.
DRAINAGE AND PERMEABILITY: Moderately well drained. The potential for surface water runoff is medium. Permeability is moderate in the solum and slow in the underlying till that contains a strongly developed paleosol. Because of the underlying paleosol, these soils have a perched water table seasonally at depths of 2 to 3.5 feet.
USE AND VEGETATION: Most areas of Harrison soils are cultivated. Corn, soybeans, and small grain are the principal crops. Native vegetation is prairie grasses.
DISTRIBUTION AND EXTENT: Southwestern Illinois. Harrison soils are moderately
extensive.
MLRA OFFICE RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Schuyler County, Illinois, 1930.
REMARKS: The sequence of materials for the Harrison series is Peoria loess over coarser textured Roxana silts over Illinoian till that contains a paleosol. The pedon has been described to a depth of 70 inches to show the materials that affect interpretations.
Diagnostic horizons and features recognized in this pedon are: mollic epipedon - the zone from the surface of the soil to a depth of 10 inches (Ap horizon); argillic horizon - the zone from about 14 to 65 inches (Bt1, Bt2, Bt3, Bt4, and 2Btg horizons).