LOCATION BLAIR ILEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Aquic Hapludalfs
TYPICAL PEDON: Blair silt loam - on a severely eroded northeast-facing slope of 14 percent in a cultivated field at an elevation of about 485 feet above mean sea level. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 5 inches; yellowish brown (10YR 5/4) silt loam, light yellowish brown (10YR 6/4) dry; moderate coarse angular clods parting to weak fine subangular blocky structure; firm; few faint brown (10YR 4/3) organic coatings on faces of peds; few fine grayish brown (10YR 5/2) peds of silty clay loam; common fine distinct yellowish brown (10YR 5/6) masses of iron accumulation in the matrix; 3 percent sand; slightly acid; abrupt smooth boundary. (4 to 10 inches thick)
Bt1--5 to 12 inches; grayish brown (10YR 5/2) silty clay loam; moderate medium subangular blocky structure; friable; few distinct very dark grayish brown (10YR 3/2) organic coatings and common distinct brown (10YR 4/3) clay films on faces of peds; common medium prominent strong brown (7.5YR 5/6) masses of iron accumulation in the matrix; 14 percent sand and one percent fine pebbles; very strongly acid; clear smooth boundary.
Bt2--12 to 20 inches; grayish brown (10YR 5/2) silt loam;weak medium prismatic structure parting to moderate medium subangular blocky; friable; few distinct dark grayish brown (10YR 4/2) clay films on faces of peds; common fine distinct yellowish brown (10YR 5/6) masses of iron accumulation in the matrix; 15 percent sand; very strongly acid; gradual smooth boundary.
Bt3--20 to 30 inches; dark grayish brown (10YR 4/2) and grayish brown (10YR 5/2) silt loam; moderate medium prismatic structure parting to moderate medium subangular blocky; friable; few distinct dark gray (10YR 4/1) clay films on faces of peds; common medium distinct dark yellowish brown (10YR 4/4) masses of iron accumulation in the matrix; 18 percent sand and 2 percent fine and medium pebbles; strongly acid; clear smooth boundary.
Bt4--30 to 36 inches; light brownish gray (10YR 6/2) silt loam; weak medium prismatic structure parting to weak medium subangular blocky; friable; few distinct dark grayish brown (10YR 4/2) clay films on faces of peds; common medium faint grayish brown (10YR 5/2) iron depletions and many medium distinct dark yellowish brown (10YR 4/4) masses of iron accumulation in the matrix; common fine black (10YR 2.5/0) iron-manganese nodules; 20 percent sand and 2 percent fine and medium pebbles; slightly acid; clear smooth boundary.
Btg--36 to 47 inches; light brownish gray (2.5Y 6/2) silt loam; weak medium prismatic structure parting to weak medium subangular blocky; friable; few faint grayish brown (10YR 5/2) clay films on faces of peds;common medium prominent dark brown (7.5YR 4/4) masses of iron accumulation in the matrix; one percent fine and medium pebbles; 15 percent sand; neutral; clear smooth boundary. (Combined thickness of the Bt and Btg horizons is 36 to 58 inches.)
BCg--47 to 55 inches; gray (10YR 6/1) silt loam; weak coarse prismatic structure; friable; many coarse prominent yellowish red (5YR 4/6) and few medium distinct yellowish brown (10YR 5/6) masses of iron accumulation and few faint gray (10YR 5/1) iron depletions in the matrix; one percent fine and medium gravel; 22 percent sand; neutral; gradual smooth boundary. (0 to 20 inches thick)
Cg--55 to 71 inches; gray (5Y 6/1) silt loam; massive; friable; common coarse prominent yellowish brown (10YR 5/6) masses of iron accumulation and few fine faint gray (5Y 5/1) iron depletions in the matrix; 2 percent fine and medium pebbles; 20 percent sand; neutral; clear smooth boundary.
2Btgb--71 to 80 inches; gray (5Y 6/1) clay loam; weak coarse prismatic structure parting to weak coarse subangular blocky; firm; common distinct dark gray (5Y 4/1) clay films on faces of peds; many coarse prominent strong brown (7.5YR 5/6) masses of iron accumulation in the matrix; about 5 percent fine and medium pebbles; slightly alkaline.
TYPE LOCATION: Perry County, Illinois; about 7 miles north and 4.5 miles east of Pinckneyville; 1280 feet north and 700 feet west of the center of sec. 15, T. 4 S., R. 2 W.; USGS Todds Mill, Il. topographic quadrangle; lat. 38 degrees 10 minutes 55 seconds N. and long. 89 degrees 18 minutes 30 seconds W.
RANGE IN CHARACTERISTICS: The depth to the base of the argillic horizon is 40 to 68 inches. The particle-size control section averages 25 to 35 percent clay, 10 to 25 percent sand, and less than 10 percent gravel by volume. Commonly about one-third to one-half of the sand is very fine.
The upper part of the series control section (Ap, A, and E) has hue of 10YR, value of 4 or 5 (6 or 7 dry) and chroma of 2 to 4. Texture is silt loam or loam, except some eroded pedons are silty clay loam or clay loam. Clay content is 20 to 35 percent. Reaction is strongly acid to slightly acid except in pedons that have been limed range to neutral.
In some eroded pedons the E horizon has been mixed into the Ap horizon.
The middle part of the series control section (Bt horizons that formed in silty sediments) has value of 4 to 6 and chroma of 2 to 4 in the upper part. In the middle and lower part it has hue of 10YR, 2.5Y, or less commonly 5Y; value of 4 to 6; and chroma of 1 or 2. Redoximorphic features have hue of 7.5YR, 10YR, or 2.5Y; value of 4 to 6; and chroma of 1 to 8. Clay films have chroma of 2 or 3 in the upper part and 1 or 2 in the lower part. The Bt horizon is silty clay loam, silt loam, clay loam, or loam. Reaction is very strongly acid to moderately acid in the upper part and strongly acid to slightly alkaline in the lower part. Some pedons have a 2Bt horizon in the lower part formed in accretion gley or in till that contains a strongly developed paleosol.
Pedons with a BC horizon have hue of 10YR or 2.5Y, value of 4 to 6, and chroma of 1 or 2. Colors of redoximorphic features are in the range as defined for the Bt horizon and also include 5YR hue. Texture is silt loam, loam, silty clay loam, or clay loam, and reaction is moderately acid to slightly alkaline.
The lower part of the control section (Cg) has hue of 10YR, 2.5Y, or 5Y; value of 4 to 6; and chroma of 1 or 2. It has redoximorphic features. Texture is silt loam or loam, and reaction is moderately acid to slightly alkaline.
Some pedons have a C horizon that is underlain by buried horizons of older soils and other pedons do not have a C horizon; where the modern soil is welded to the paleosol.
COMPETING SERIES: These are the Appleriver, Bunkum, Fishhook, Geff, Glenford, Henshaw, Ingersoll, Keene, Lykens, Muren, Torox, Travilah, and Xenia series.
Appleriver soils have a paralithic contact at 45 to 60 inches. Bunkum, Geff and Muren soils average less than 7 percent sand in the upper part of the series control section and contain less rock fragments in the lower part of the series control section. Fishhook soils averages more than 35 percent clay in the lower part of the series control section. Glenford soils do not have a matrix color with chroma of 2 or less in the lower part of the series control section. Henshaw, Ingersoll, Lykens, Torox, and Xenia soils contain carbonates in the lower part of the series control section. Keene soils have a paralithic contact at depths of 40 to 84 inches. Travilah soils have a lithic contact at 20 to 40 inches.
GEOGRAPHIC SETTING: Blair soils are on gently sloping to moderately steep parts of dissected Illinoian till plains. Slope ranges from 2 to 20 percent. These soils primarily formed in silty, water-worked sediments that lie in a stratigraphic position between the Wisconsinan age Peoria loess and the Illinoian till that contains a strongly developed paleosol. Some pedons have the lower part of the solum formed in till. Some pedons have a mantle of loess on the surface as much as 20 inches in thickness. Mean annual temperature is 54 to 57 degrees F., mean annual precipitation is 36 to 44 inches, frost-free period is 180 to 200 days, and elevation is 350 to 800 feet above mean sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Atlas, Bluford, Darmstadt, Grantfork, Hickory, Hosmer, Hoyleton, Marine, and Ursa soils. Atlas and Ursa soils formed in the strongly developed paleosol in the till and are downslope from the Blair soils. Bluford, Darmstadt, Hosmer, Hoyleton, Marine, and Stoy soils are upslope from the Blair soils where the loess is thicker. Bluford soils contain more clay in the control section and have fragic properties in the lower part of the solum. Darmstadt soils have a natric horizon. Hosmer soils have fragic properties in the lower part of the solum. Hoyleton and Marine soils contain more clay in the control section. Grantfork soils have a concentration of exchangeable sodium in the subsoil and contain more fine sand and coarser sand in the control section. They are on adjacent or nearby parts of the landscape. Hickory soils formed in till and contain more sand in the control section.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained. The potential for surface water runoff is medium or high. Permeability is moderately slow. In drained areas, depth to an intermittent apparent high water table is 0.5 foot to 2.0 feet from December to April in most years.
USE AND VEGETATION: Most areas are cropped. 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: Southern and western Illinois. Extent is large, and mainly in MLRA(s) 113 and 114.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Lawrence County, Illinois, 1932.
REMARKS: Blair soils are not considered to have an aquic moisture regime. Soil colors with chroma of 2 in the upper part of the solum are believed to be relict. Severe erosion has truncated the typical pedon so that the Ap horizon is underlain immediately by a horizon with these grayer colors and mottles.
ADDITIONAL DATA: Data for the typical pedon, 79IL-145-8, are attached. Data for other pedons are on file at the SCS Illinois state office.