LOCATION VARNA IL+IN WIEstablished Series
TAXONOMIC CLASS: Fine, illitic, mesic Oxyaquic Argiudolls
TYPICAL PEDON: Varna silt loam - on a northwest-facing, convex slope of 3 percent in a cultivated field at an elevation of about 220 meters (722 feet) above mean sea level. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 20 cm (0 to 8 inches); very dark gray (10YR 3/1) silt loam, gray (10YR 5/1) dry; moderate fine granular structure; friable, neutral; abrupt smooth boundary.
A--20 to 30 cm (8 to 12 inches); very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) dry; moderate fine granular structure; friable; slightly acid; clear smooth boundary. [Combined thickness of the A horizon is 25 to 41 cm (10 to 16 inches).]
2Bt1--30 to 46 cm (12 to 18 inches); brown (10YR 4/3) silty clay loam; moderate very fine subangular blocky structure; firm; many distinct very dark gray (10YR 3/1) organo-clay films on faces of peds; 5 percent gravel, moderately acid; clear smooth boundary.
2Bt2--46 to 61 cm (18 to 24 inches); dark yellowish brown (10YR 4/4) silty clay; weak fine prismatic structure parting to moderate very fine and fine subangular blocky; firm; many distinct very dark grayish brown (10YR 3/2) organo-clay films on faces of peds; 5 percent gravel; moderately acid; clear smooth boundary.
2Bt3--61 to 76 cm (24 to 30 inches); light olive brown (2.5Y 5/4) silty clay; weak fine prismatic structure parting to moderate fine angular and subangular blocky; firm; common distinct dark grayish brown (10YR 4/2) clay films on faces of peds; many fine distinct yellowish brown (10YR 5/6) masses of oxidized iron in the matrix; 5 percent gravel; neutral; clear wavy boundary.
2Bt4--76 to 107 cm (30 to 42 inches); 60 percent yellowish brown (10YR 5/6) and 40 percent grayish brown (2.5Y 5/2) silty clay loam; moderate medium prismatic structure parting to moderate fine and medium angular and subangular blocky; firm; few distinct dark grayish brown (10YR 4/2) clay films on vertical faces of peds; 5 percent gravel; slightly effervescent; slightly alkaline; gradual smooth boundary. [Combined thickness of the 2Bt horizon is 23 to 89 cm (9 to 35 inches).]
2BCt--107 to 122 cm (42 to 48 inches); 50 percent yellowish brown (10YR 5/6) and 50 percent gray (5Y 5/1) silty clay loam; weak medium prismatic structure parting to weak medium subangular and angular blocky; firm; few distinct dark grayish brown (10YR 4/2) clay films on vertical faces of peds; 2 percent gravel; slightly effervescent; moderately alkaline; gradual wavy boundary. [8 to 38 cm (3 to 15 inches) thick]
2Cd--122 to 152 cm (48 to 60 inches); 90 percent yellowish brown (10YR 5/4 and 10YR 5/6) and 10 percent gray (5Y 5/1) silty clay loam; massive; very firm; 5 percent gravel; strongly effervescent; moderately alkaline.
TYPE LOCATION: Kankakee County, Illinois; 35 feet (11 meters) north and 860 feet (262 meters) east of the southwest corner of sec. 6, T. 29 N., R. 11 E.; USGS Hersher topographic quadrangle; lat. 41 degrees 00 minutes 53 seconds N. and long. 88 degrees 00 minutes 49 seconds W., NAD 27; UTM Zone 16T, 414761 easting and 4540891 northing, NAD 83
RANGE IN CHARACTERISTICS: The depth to the base of soil development commonly is 91 to 122 cm (36 to 48 inches) and ranges from 61 to 152 cm (24 to 60 inches). The thickness of the mollic epipedon commonly ranges from 25 to 41 cm (10 to 16 inches), but can range to 8 inches (20 cm) for the 1/3 solum rule. The depth to carbonates ranges from 61 to 107 cm (24 to 42 inches). The particle-size control section averages between 35 and 50 percent clay. The series control section contains from 5 to 20 percent sand and as much as 10 percent by volume rock fragments throughout.
The Ap, A, or AB horizon has hue of 10YR, value of 2 or 3, and chroma of 1 or 2. Texture is silt loam or loam, but silty clay loam is recognized in eroded or severely eroded pedons. Reaction ranges from moderately acid to slightly alkaline depending upon liming practices.
The Bt or 2Bt horizon has hue of 10YR or 2.5Y, value of 4 through 6, and chroma of 3 or 4 in the upper part and 1 to 4 in the lower part. In some pedons the lower part of the Bt or 2Bt horizon has hue of 5Y. Redoximorphic features have chroma that ranges from 1 to 6. Texture is silty clay loam, silty clay, or less commonly clay. Reaction ranges from moderately acid to slightly alkaline.
The BC, 2BC, Cd, or 2Cd horizon has hue of 10YR, 2.5Y, or 5Y; value of 4 to 6; and chroma of 1 to 6. Texture is silty clay loam or clay loam but contains subhorizons of loam or silty clay in some pedons. It averages between 27 and 40 percent clay. Reaction ranges from neutral to moderately alkaline and commonly contains carbonates. Bulk density of the Cd or 2Cd horizons ranges from 1.7 to 1.9 gm/cc.
COMPETING SERIES: This is the only series in the family.
GEOGRAPHIC SETTING: Varna soils typically are on convex slopes of the relatively undissected till plains of Wisconsinan Age. Slope ranges from 1 to 20 percent. These soils formed in calcareous silty clay loam or clay loam till. In many places they have a surface layer of loess or silty material less than 46 cm (18 inches) thick. Mean annual air temperature ranges from 7 to 12 degrees C (45 to 53 degrees F), mean annual precipitation ranges from 711 to 1016 mm (28 to 40 inches), frost-free period ranges from 140 to 180 days, and elevation ranges from 165 to 311 meters (541 to 1020 feet) above sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ashkum, Elliott, Markham, Morley, and Ozaukee soils. The poorly drained Ashkum soils and somewhat poorly drained Elliott soils form a drainage sequence with Varna soils. Typically, they are on lower parts of the landform and have lower slope gradients. Markham, Morley, and Ozaukee soils are on nearby similar landforms but lack mollic epipedons.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Moderately well drained. The depth to a perched seasonal high water table is 61 to 107 cm (2.0 to 3.5 feet) at some time between February and April in most years. The potential for surface runoff is medium to very high. Saturated hydraulic conductivity is moderately low or moderately high (0.42 to 1.41 micrometers per second). Permeability is slow.
USE AND VEGETATION: Most areas are cultivated. Corn, soybeans, small grain, and meadow are the principal crops. Native vegetation is prairie grass.
DISTRIBUTION AND EXTENT: Eastern and northern Illinois, southeastern Wisconsin, and northern Indiana. The series is of moderate extent in MLRAs 95B, 108A, 108B, 110, 111C, 111D, and 115C.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana.
SERIES ESTABLISHED; Marshall County, Illinois, 1934.
Diagnostic horizons and features recognized in this pedon are: mollic epipedon - the zone from the surface to a depth of 12 inches (30 cm) (Ap and A horizons); argillic horizon - the zone from about 12 to 42 inches (30 to 107 cm) (2Bt1, 2Bt2, 2Bt3, and 2Bt4 horizons); udic moisture regime.