LOCATION TUNICA MS+AR KY LA MO TNEstablished Series
TAXONOMIC CLASS: Clayey over loamy, smectitic over mixed, superactive, nonacid, thermic Vertic Epiaquepts
TYPICAL PEDON: Tunica clay--forest. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 3 inches; dark gray (10YR 4/1) clay; moderate fine and medium subangular blocky structure; firm, moderately sticky, moderately plastic; slightly acid; clear smooth boundary. (3 to 12 inches thick).
Bg1--3 to 15 inches; dark gray (2.5Y 4/1), exterior, and dark grayish brown (2.5Y 4/2), interior, silty clay; moderate fine and medium subangular blocky structure; firm, very sticky, very plastic; common shiny pressure faces; few non-intersecting slickensides; slightly acid; gradual wavy boundary. (10 to 15 inches thick).
Bg2--15 to 26 inches; dark gray (2.5Y 4/1) exterior, and dark grayish brown (2.5Y 4/2), interior silty clay; moderate fine and medium subangular blocky structure; firm, very sticky, very plastic; common shiny pressure faces; few non-intersecting slickensides; slightly acid; clear smooth boundary. (7 to 14 inches thick).
2CBg--26 to 33 inches; dark grayish brown (10YR 4/2) silt loam; weak fine granular structure; friable, nonsticky, nonplastic; fine and medium distinct irregular yellowish brown (10YR 5/4) masses of oxidized iron in matrix; clay films lining pores; fine and medium distinct irregular gray (2.5Y 5/1) masses of reduced iron in matrix; fine prominent irregular yellowish brown (10YR 5/6) masses of oxidized iron in matrix; moderately alkaline; clear smooth boundary.
2Cg1--33 to 55 inches; dark grayish brown (10YR 4/2) statified very fine sandy loam; structureless massive; friable, nonsticky, nonplastic; fine and medium distinct irregular yellowish brown (10YR 5/6) masses of oxidized iron in matrix; fine distinct irregular yellowish brown (10YR 5/4) masses of oxidized iron in matrix; moderately alkaline; gradual wavy boundary.
2Cg2--55 to 63 inches; grayish brown (10YR 5/2) statified very fine sandy loam; structureless massive; loose, nonsticky, nonplastic; fine and medium distinct irregular yellowish brown (10YR 5/4) masses of oxidized iron in matrix; fine and medium distinct irregular yellowish brown (10YR 5/6) masses of oxidized iron in matrix; moderately alkaline; clear wavy boundary.
2Cg3--63 to 80 inches; grayish brown (10YR 5/2) statified very fine sandy loam; loose, nonsticky, nonplastic; fine and medium distinct irregular yellowish brown (10YR 5/4) masses of oxidized iron in matrix; medium prominent irregular yellowish brown (10YR 5/6) masses of oxidized iron in matrix; fine and medium distinct irregular masses of oxidized iron in matrix; moderately alkaline.
TYPE LOCATION: Tunica County, Mississippi; located 6.2 miles north on Hgy. 61 from the intersection with Hgy. 4 in Tunica, Ms., then 3.5 miles west on county road to levee, then 1.5 miles northwest on a woods trail to a small clearing, then 1,000 feet east-northeast into woods; 2,450 feet east and 2,150 feet south of the NW corner Sec. 36, T. 3 S., R. 12 W.; 34 degrees, 46 minutes, 51.73 seconds N. Latitude, 90 degrees, 25 minutes, 22.34 seconds W. Longitude, Council, Arkansas USGS 7.5 Minute Quadrangle.
RANGE IN CHARACTERISTICS:
Solum thickness: 20 to 36 inches
Clay content in the Control Section: 35 to 75 percent above the discontinuity; and 10 to 32 percent below the discontinuity.
Redoximorphic features: Depleted matrix and iron concentrations in shades of brown throughout the solum.
Other distinctive soil features: Depth to the contrasting loamy discontinuity ranges from 20 to 36 inches.
Concentrated minerals: None
A horizon:
Color--Hue of 10YR or 2.5Y, value of 4 or 5, and chroma of 1 or 2, or it is neutral with value of 4, and chroma of 0. Some pedons have a A horizon that is less than 6 inches thick with hue of 10YR or 2.5Y, value of 3, and chroma of 2.
Redoximorphic features--None
Texture--silty clay or clay. Some pedons have an overwash of silt loam or silty clay loam.
Other features--None
Reaction--Moderately acid to slightly alkaline, except where limed
Bg horizon:
Color--The upper part has hue of 10YR, 2.5Y, or 5Y, value of 4 or 5, and chroma of 1, or value of 6, and chroma of 1 or 2, or it is neutral with value of 4 to 6, and chroma of 0. The lower part has hue of 10YR, 2.5Y, or 5Y, value of 4 to 6, and chroma of 1 or 2. In some pedons, it is neutral, with value 4 to 6 and chroma of 0.
Redoximorphic features--Iron concentrations in shades of brown are few to common throughout the B horizon.
Texture--Silty clay or clay
Other features--Pressure faces and slickensides
Reaction--Moderately acid to slightly alkaline
2CB or 2BC horizon: (where present)
Color--Hue of 10YR, 2.5Y, or 5Y, value of 4 to 6, and chroma of 1 or 2. In some pedons, it is neutral, with value 4 to 6 and chroma of 0.
Redoximorphic features--Iron concentrations in shades of brown are few to common throughout.
Texture--Silt loam, loam, silty clay loam, sandy loam, fine sandy loam or very fine sandy loam
Other features--Weak, subangular blocky structure and faint clay films on pores and ped faces in some pedons.
Reaction--Moderately acid to moderately alkaline
2C horizon:
Color--Hue of 10YR, 2.5Y, or 5Y, value of 4 to 6, and chroma of 1 or 2. In some pedons, it is neutral, with value 4 to 6 and chroma of 0; also, below a depth of 30 inches, some pedons are variegated in shades of brown, yellow, and gray.
Redoximorphic features--Iron concentrations in shades of brown are few to common throughout.
Texture--Silt loam, loam, silty clay loam, sandy loam, fine sandy loam or very fine sandy loam, and the lower part in some pedons is loamy fine sand.
Other features--None
Reaction--Moderately acid to moderately alkaline
COMPETING SERIES: The Keyespoint series is the only other series in the same family. The Alligator, Bowdre, Earle, Forestdale, Newellton, Perry, Sharkey, and Tensas soils are in closely related families. Keyespoint soils have value of 4 or 5 and chroma of 2 in the upper part of the Bg horizon and are somewhat poorly drained. Alligator, Perry, and Sharkey soils have a very-fine particle-size class and do not have a contrasting texture within a depth of 40 inches. Bowdre and Newellton soils have a clayey upper solum that is less than 20 inches thick over loamy material; also, Bowdre soils have a mollic epipedon. Earle soils have an acid reaction class. Forestdale and Tensas soils have an argillic horizon.
GEOGRAPHIC SETTING: Tunica soils are on flood plains of the lower Mississippi River and its tributaries in the Southern Mississippi Valley Alluvium Major Land Resource Area (MLRA 131A). Slope gradients are mainly less than 3 percent, but the range is from 0 to 5 percent. Areas not protected by levees are flooded for brief periods. The soil formed in clayey alluvium 20 to 36 inches thick, and the underlying loamy alluvium. The climate is warm and humid. Mean annual temperature is about 67 degrees Fahrenheit, and mean annual precipitation is about 55 inches near the type location.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the closely related Bowdre, Earle, Forestdale, Newellton, and Sharkey series and the Bruin, Commerce, Convent, and Mhoon series. Bruin soils have a cambic horizon with a brown matrix and are coarse-silty in the 40-inch particle-size control section. Commerce and Mhoon soils are fine-silty in the 10- to 40-inch particle-size control section. Convent soils are coarse-silty in the 10- to 40-inch particle-size control section. All these soils are associated across the nearly linear surface of the broad floodplain of the Mississippi River.
DRAINAGE AND PERMEABILITY: Poorly drained; rate of runoff is high on slopes less than 1 percent, and very high on slopes of 1 percent or more; very slow permeability in the clay horizons and moderate in the loamy horizon. These soils are flooded unless protected by levees, especially during the spring and fall months. They are saturated in the surface layer and along cracks and slickenside faces in the subsoil during December through April in normal years. Water runs off the surface at a high to very high rate.
USE AND VEGETATION: Most of the Tunica soils are used for growing cotton, soybeans, small grains, corn, hay, and pasture. A small amount is in bottomland hardwoods. Important commercial trees are cherrybark oak, eastern cottonwood, green ash, Nuttall oak, sweetgum, and American sycamore. Other trees include elm, water oak, hackberry, pecan, and water hickory.
DISTRIBUTION AND EXTENT: Arkansas, Kentucky, Louisiana, Mississippi, Missouri, and Tennessee. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Little Rock, Arkansas
SERIES ESTABLISHED: Tunica County, Mississippi; 1949.
REMARKS: The series type location pedon was moved from Adams County, Mississippi, to Tunica County, Mississippi in 2004. Lab data for samples from the type location pedon were run at Mississippi State University (S01-MS143-003). Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to a depth of about 3 inches (Ap horizon).
Cambic horizon - the zone from approximately 3 to 26 inches (Bg1, Bg2 horizons).
Slickensides that do not intersect - (Bg2 horizon).