LOCATION UNA MS+AL AR LA NC TNEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, acid, thermic Typic Epiaquepts
TYPICAL PEDON: Una silty clay-cultivated. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 5 inches; very dark grayish brown (10YR 3/2) silty clay; moderate medium granular structure; friable, plastic, sticky; common fine roots; strongly acid; abrupt smooth boundary. (4 to 6 inches thick)
Bgc1--5 to 14 inches; light gray (5Y 7/1) clay; common medium distinct yellowish brown (10YR 5/6) mottles; moderate fine blocky and subangular structure; firm, very plastic, very sticky; few fine roots; common fine brown concretions; cracks and root channels filled with material from the Ap horizon; very strongly acid; gradual wavy boundary.
Bgc2--14 to 30 inches; light gray (5Y 7/1) clay; common medium distinct yellowish brown (10YR 5/6) mottles; moderate fine blocky structure; firm, very plastic, very sticky; few fine roots; common fine brown concretions; few fine black concretions; cracks and root channels filled with material from the Ap horizon; very strongly acid; gradual wavy boundary. (Combined thickness of the upper part of the Bg horizon is 14 to 40 inches.)
Bgc3--30 to 60 inches; gray (5Y 5/1) clay; common medium distinct yellowish brown (10YR 5/6) mottles; moderate medium blocky structure; firm, very plastic, very sticky; few slickensides that do not intersect; common fine and medium brown concretions; cracks and root channels filled with material from the Ap horizon; very strongly acid.
TYPE LOCATION: Lee County, Mississippi; 4.0 miles north of Tupelo on U.S. Highway 45, 1.0 mile east along Mud Creek, 0.2 mile east of railroad and 880 feet south of gravel road. NW1/4sec. 8, T. 9 S., R. 6 E.
RANGE IN CHARACTERISTICS: Thickness of solum exceeds 60 inches. Reaction of the soil is very strongly acid or strongly acid, except for the surface layers in areas that have been limed. Some pedons are medium acid to neutral below a depth of 40 inches.
The A horizon has hue of 10YR, 2.5Y, or 5Y, value of 3 to 7, and chroma of 1 or 2. Where value is 3, thickness is 6 inches or less. It is silty clay loam, silty clay, clay, clay loam, sandy clay loam, or loam.
The B horizon has hue of 10YR, 2.5Y, or 5Y, value of 4 to 7, and chroma of 1 or 2, with mottles in shades of brown or yellow. Texture is silty clay loam, silty clay, or clay. In most pedons, the coefficient of linear extensibility increases with depth in the lower part of the Bt horizon and commonly is .09 or more below a depth of 30 inches. Brown and black concretions are few to common in the B horizon.
COMPETING SERIES: Tamba is the only other series in the same family. Closely related soils include the Alligator, Chastain, Houlka, Kinston, Leeper, Tuscumbia, and Urbo series. Tamba soils are in Southern California. Alligator soils have montomorillonitic mineralogy and are very-fine in the 10- to 40-inch particle-size control section. Chastain soils have kaolinitic mineralogy. Houlka, Leeper, and Urbo soils have colors with a higher chroma between the base of the Ap horizon and a depth of 30 inches. Kinston soils are fine-loamy in the particle-size control section. Tuscumbia soils are medium acid to moderately alkaline throughout and have as much as 20 inches or more of material within a depth of 40 inches that has a coefficient of linear extensibility greater than .09.
GEOGRAPHIC SETTING: Una soils are on flood plains of streams that drain areas of the Southern Coastal Plain and Blackland Prairie Major Land Resource Areas. Slopes mainly are less than one percent and range to 4 percent. This soil formed in acid clayey alluvium. The climate is warm and humid; average annual precipitation is about 52 inches, and the average annual temperature is about 63 degrees Fahrenheit, near the type location.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Houlka, Kinston, Leeper, Rosebloom, Tuscumbia, and Urbo soils. The soils are associated across the nearly linear surface of floodplains. The somewhat poorly drained Houlka, Leeper, and Urbo soils are slightly higher positions on low swells or near incised channels. The poorly drained Kinston soils are mainly along channels. The poorly drained Tuscumbia soils are mainly in back swamps. The poorly drained Rosebloom soils, which have a fine-silty particle-size control section, are in similar positions as the Una soils.
DRAINAGE AND PERMEABILITY: Poorly drained, very slow runoff, and permeability. During the winter and early in spring, these soils are subject to occasional or frequent flooding for brief to long duration and the water table is within one foot of the surface.
USE AND VEGETATION: Most areas are in the forest or pasture. Wooded areas are in bottomland hardwoods. Common trees are sweetgum, eastern cottonwood, green ash, cherrybark oak, Nuttall oak, willow oak, water oak and water tupelo. Cleared and drained areas are used for growing pasture, hay, corn, and soybeans.
DISTRIBUTION AND EXTENT: Alabama, Arkansas, Louisiana, Mississippi and North Carolina. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Auburn, Alabama
SERIES ESTABLISHED: Mississippi Agricultural and Forestry Experiment Station, Oktibbeha County, Mississippi; 1950.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to a depth of about 5 inches (Ap horizon).
Cambic horizon - the zone from approximately 5 to 60 inches (Bgc1, Bgc2, Bgc3 horizons).
Haplaquepts feature - gray and mottled below the surface layer (Bgc1, Bgc2, Bgc3 horizons).