LOCATION SIWELL MSEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, active, thermic Typic Hapludalfs
TYPICAL PEDON: Siwell silt loam--pasture.
(Colors are for moist soils unless otherwise stated.)
Ap--0 to 4 inches; dark brown (10YR 4/3) silt loam; weak fine granular structure; friable; many fine roots; strongly acid; abrupt smooth boundary. (2 to 8 inches thick)
Bt1--4 to 8 inches; dark brown (7.5YR 4/4) silty clay loam; moderate medium subangular blocky structure; friable; many fine roots; common patchy clay films on faces of peds; strongly acid; gradual smooth boundary.
Bt2--8 to 13 inches; strong brown (7.5YR 5/6) silty clay loam; weak medium subangular blocky structure; friable; common fine roots; common patchy clay films on faces of peds; strongly acid; clear smooth boundary.
Bt3--13 to 21 inches; yellowish brown (10YR 5/6) silty clay loam; few fine distinct pale brown (10YR 6/3) mottles; weak medium subangular blocky structure; friable; few fine roots; few patchy clay films on faces of peds; common fine black and brown concretions; very strongly acid; clear smooth boundary.
Bt4--21 to 30 inches; yellowish brown (10YR 5/6) silty clay loam; many fine and medium distinct grayish brown (10YR 5/2) mottles; weak medium subangular blocky structure; firm; few fine roots; few patchy clay films on faces of peds; few black and brown concretions; very strongly acid; clear wavy boundary. (Combined thickness of the Bt subhorizons is 18 to 32 inches)
2Bt5--30 to 39 inches; mottled yellowish brown (10YR 5/6), pale brown (10YR 6/3), and grayish brown (10YR 5/2) silty clay loam; moderate medium subangular blocky structure; firm; plastic; few fine roots; stress surfaces or clay films, or both, on faces of peds; few fine black concretions; very strongly acid; gradual wavy boundary. (4 to 15 inches thick)
2C--39 to 72 inches; mottled light olive brown (2.5Y 5/4), yellowish brown (10YR 5/4), and grayish brown (10YR 5/2) clay; intersecting slickensides parting to moderate medium angular blocky fragments; very firm; very plastic; shiny faces on peds; common light gray soft accumulations of calcium carbonate; few fine black and brown concretions; neutral.
TYPE LOCATION: Hinds County, Mississippi; 1100 feet south of U. S. Highway 80 and Robinson Road intersection. NW1/4SW1/4 sec. 1, T. 5 N., R. 1 E.
RANGE IN CHARACTERISTICS: The solum ranges from 24 to 55 inches in thickness. Thickness of the silty upper part is 20 to 40 inches. The A, E, and Bt horizons range from very strongly acid to medium acid. The 2Bt horizon ranges from very strongly acid to moderately alkaline. The 2C horizon ranges from neutral to moderately alkaline.
The A horizon has hue of 7.5YR or 10 YR, value of 4 or 5, and chroma of 3 or 4. It is silt loam or silty clay loam.
The E horizon, if present, has hue of 10YR, value of 5 or 6, and chorma of 3 or 4. It is silt loam.
The Bt subhorizons have hue of 7.5YR, value of 4 or 5, and chroma of 4 to 8, or they have hue of 10YR, value of 5, and chroma of 6; and some part of the upper 10 inches of the Bt horizon has a matrix with value of 5 or 6. In some pedons the lower part of the Bt horizon has few to common mottles in shades of brown, gray, or red. The Bt horizon is silt loam or silty clay loam, and the upper 20 inches has from 20 to 35 percent clay.
The 2Bt horizon commonly is mottled in shades of brown, red, or gray. Less commonly it has a matrix in hue of 10YR, 2.5Y or 5Y, value of 3 to 6, and chroma of 4 to 6 mottles are few to many in shades of gray and brown. The 2Bt horizon is silty clay loam or silty clay.
The 2C horizon has the same range in color as the 2B horizon. Soft accumulations or nodules of calcium carbonate, if present, are few to many.
COMPETING SERIES: These are the Dubbs, Gallion, Memphis, and Rilla soils in the same family and the closely related Falkner, Freestone, Loring, Muskogee, Providence, Tippah, and Vian series. Dubbs, Gallion, Memphis, Rilla, and Vian soils do not have clayey horizons. Falkner and Tippah soils have a acid clayey 2Bt horizon. Freestone soils have a fine-loamy particle size class. Loring and Providence soils have a fragipan. Muskogee soils have mottles with chroma of 2 or less in the upper 10 inches of the argillic horizon.
GEOGRAPHIC SETTING: Siwell soils are on uplands of the Southern Mississippi Valley Silty Uplands Major Land Resource Area. These are nearly level to moderately steep soils. Slopes range from 0 to 15 percent. The soil formed in a silty mantle, 20 to 40 inches thick, and the underlying calcareous clays. The climate is warm and humid. The mean annual temperature is about 65 degrees Fahrenheit and the mean annual precipitation is about 51 inches near the type location.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Loring and Providence series and the Byram and Kipling series, all of which are in similar landscape positions as the Siwell soils. Byram soils have a fragipan. Kipling soils are fine in the particle size control section.
DRAINAGE AND PERMEABILITY: Moderately well drained; medium to rapid runoff; moderate permeability in the upper part, and very slow in the lower part. In wet seasons late in winter and early in spring water is perched at a depth of 2.5 to 3 feet above the clayey layer.
USE AND VEGETATION: A large part of the acreage of the Siwell soils is in urban areas. A small acreage is used for growing pasture, hay, cherrybark oak, white oak, post oak, southern red oak, hickory, sweetgum, shortleaf pine, and loblolly pine.
DISTRIBUTION AND EXTENT: Mississippi; the series is of minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Auburn, Alabama
SERIES ESTABLISHED: Hinds County, Mississippi; 1976.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to a depth of about 4 inches (Ap horizon).
Argillic horizon - the zone from approximately 4 to 39 inches (Bt1, Bt2, Bt3, Bt4, 2Bt5 horizons).
Underlying calcareous clay - the zone from approximately 30 to 72 inches (2C horizon).
ADDITIONAL DATA: Chemical and Physical Analyses and Engineering Test Data for two pedons are published respectively in Soil Survey Hinds County, Mississippi (issued March 1979) pp. 110-111 and Soil Survey Madison County, Mississippi (issued February 1984) pp. 141-145.