LOCATION SESSUM MS+AR
Established Series
Rev. FVB:WMK:RBH
10/2018
SESSUM SERIES
The Sessum series consists of deep, poorly drained, very slowly permeable soils formed in acid clayey materials and the underlying calcareous clay or chalk. They are on uplands in the Blackland Prairie Major Land Resource Area. Slopes range from 0 to 5 percent.
TAXONOMIC CLASS: Fine, smectitic, thermic Chromic Dystraquerts
TYPICAL PEDON: Sessum silty clay--cultivated. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 6 inches; dark grayish brown (10YR 4/2) silty clay; weak fine granular and subangular blocky structure; firm; common fine roots; common fine brown and black concretions; very strongly acid; abrupt smooth boundary. (4 to 8 inches thick)
Btg1--6 to 24 inches; light brownish gray (2.5Y 6/2) clay; many fine and medium distinct yellowish brown (10YR 5/6) mottles; moderate fine and medium subangular and angular blocky structure; firm, very sticky, very plastic; few fine roots; pressure faces or clay films on faces of peds; few fine brown and black concretions; very strongly acid; gradual wavy boundary.
Btg2--24 to 30 inches; light olive gray (5Y 6/2) clay; common fine and medium distinct yellowish brown (10YR 5/6) mottles; moderate fine subangular and angular blocky structure; firm, very sticky, very plastic; few fine roots; pressure faces or clay films on faces of peds; few black and brown concretions; few fine and medium slickensides that do not intersect; very strongly acid; gradual wavy boundary.
Btg3--30 to 43 inches; light olive gray (5Y 6/2) clay; common fine distinct light olive brown (2.5Y 5/4) and yellowish brown (10YR 5/6) mottles; moderate fine and medium subangular and angular blocky structure; firm, very sticky, very plastic; few fine roots; pressure faces or clay films on faces of peds; few fine black and brown concretions; common medium to coarse slickensides that do not intersect; strongly acid; gradual wavy boundary. (Combined thickness of the Btg horizon is 24 to 50 inches.)
BC--43 to 58 inches; light olive gray (5Y 6/2) clay; few fine faint gray mottles; weak fine to medium subangular and angular blocky structure; firm, very sticky, very plastic; common to many medium to coarse slickensides that intersect; few fine black and brown concretions; very strongly acid; gradual wavy boundary. (0 to 20 inches thick)
C1--58 to 68 inches; light olive brown (2.5Y 5/4) clay; common fine distinct light olive gray (5Y 6/2) mottles; massive; firm, very sticky, very plastic; few fine black and brown concretions; medium acid; gradual wavy boundary.
C2--68 to 85 inches; mottled yellowish brown (10YR 5/6) light olive gray (5Y 6/2), and olive yellow (2.5Y 6/6) clay; massive; firm, very sticky, very plastic; common fine black and brown concretions; few fine calcium carbonate nodules; moderately alkaline.
TYPE LOCATION: Oktibbeha County, Mississippi; 3.0 miles south of the intersection of State Highway 12 on State Highway 25, 130 yards west on field road and 45 feet north into field. SW1/4SW1/4 sec. 16, T. 18 N., R. 14 E.
RANGE IN CHARACTERISTICS: The solum ranges from 38 to 78 inches thick. Calcium-magnesium ratio is more than 1.0. The COLE value in the upper 20 inches of the B horizon is 0.09 or more. The soil ranges from very strongly acid to medium acid in the solum and from medium acid to moderately alkaline in the C horizon. Depth to the neutral or alkaline part of the C horizon ranges from 38 to 96 inches.
The A horizon has hue of 10YR or 2.5Y, value of 3 to 5, and chroma of 2 or 3. It is silty clay loam or silty clay.
The Bt horizon to a depth of 30 inches or more has 60 percent or more of the matrix in hue of 10YR, 2.5Y, or 5Y, value of 4 to 6, and chroma of 1 or 2, or it is neutral with value of 4 to 6 and chroma of 0; mottles in shades of brown and yellow are few to many. The lower part of the Bt horizon has the same color range as the upper part and, in addition, includes a matrix with hue of 2.5Y, value of 4 or 5, and chroma of 4, or it is mottled in shades of gray, yellow, or brown. The Bt horizon is silty clay loam, silty clay, or clay. It has from 38 to 60 percent clay.
The C horizon has the same color range as the Bt horizon. It is clay or marly clay in the upper part and marly clay or weathered chalk in the lower part. Some pedons are underlain by chalk or marl.
COMPETING SERIES: These include
Baldwin,
Mayhew,
Panola,
Tensas, and
Wilson series in the same family and the closely related
Eutaw,
Kipling, Mayhew,
Midland, and
Oktibbeha series. Baldwin soils are slightly acid to mildly alkaline in the Bt horizon and have dark coatings on surfaces of peds in the upper part of the Bt horizon. Mayhew soils have a calcium-magnesium ratio of less than 1 and are underlain by shale. Panola and Tensas soils are not as gray in the upper part of the Bt horizon. Wilson soils are in areas with less than 45 inches of rainfall and are dry in the moisture control section for longer periods. Eutaw soils are very-fine in the particle-size control section and have intersecting slickensides. Kipling and Oktibbeha soils have a Bt horizon with a chroma of 3 or more; also, Oktibbeha soils are very-fine in the particle size control section. Midland soils are slightly acid to mildly alkaline in the Bt horizon and have a COLE value of less than 0.09 in the upper 20 inches of the Bt horizon.
GEOGRAPHIC SETTING: Sessum soils are on nearly level to gently sloping uplands in the Blackland Prairie Major Land Resource Area. Slope gradients range from 0 to 5 percent. These soils formed in acid clayey sediments and the underlying calcareous clay or chalk. The climate is warm and humid. Mean annual temperature is 68 degrees Fahrenheit, and mean annual precipitation is 51.0 inches near the type location.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Eutaw,
Kipling, and
Oktibbeha soils of the competing series and the
Longview series. Eutaw, Kipling, and Oktibbeha soils are in similar landscape positions as the Sessum soils. Longview soils, which also are in similar landscape positions, have a fine-silty particle-size control section and siliceous mineralogy.
DRAINAGE AND PERMEABILITY: Poorly drained; slow runoff; very slow permeability. In wet seasons in late winter and early in spring, water is perched above the clayey layers at a depth of 6 to 18 inches.
USE AND VEGETATION: Most areas of the Sessum soils are used for growing pasture, hay, soybeans, and grain sorghum. The woodland vegetation is southern red oak, white oak, sweetgum, loblolly pine, and eastern redcedar.
DISTRIBUTION AND EXTENT: Mississippi. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Auburn, Alabama
SERIES ESTABLISHED: Oktibbeha County, Mississippi; 1971.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to a depth of about 6 inches (Ap horizon).
Argillic horizon - the zone from approximately 6 to 43 inches (Btg1, Btg2, Btg3 horizons).
Vertic features - slickensides (Btg2, Btg3, BC horizon).
ADDITIONAL DATA: Physical and chemical analyses for one pedon in Soil Survey of Noxubee County, Mississippi.
National Cooperative Soil Survey
U.S.A.