LOCATION URBO MS+AL AR LA TN TXEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, acid, thermic Vertic Epiaquepts
TYPICAL PEDON: Urbo silty clay loam--cultivated.
(Colors are for moist soil unless otherwise stated.)
Ap--0 to 5 inches; dark grayish brown (10YR 4/2) silty clay loam; common fine faint grayish brown mottles; weak fine granular structure; friable, slightly plastic; few fine roots; few fine black concretions; strongly acid; abrupt smooth boundary. (4 to 8 inches thick)
A--5 to 9 inches; grayish brown (2.5Y 5/2) silty clay loam; common fine faint dark grayish brown mottles; weak fine and medium subangular blocky structure; friable; slightly sticky; plastic, few fine roots; few fine black and brown concretions; very strongly acid; clear smooth boundary. (0 to 8 inches thick)
Bg1--9 to 18 inches; grayish brown (2.5Y 5/2) silty clay; common fine faint dark grayish brown mottles; weak medium prismatic structure parting to moderate fine and medium angular and subangular blocky; firm, very sticky; plastic, few fine roots; few stress surfaces on peds; common fine black and brown concretions; very strongly acid; clear smooth boundary. (6 to 12 inches thick)
Bg2--18 to 29 inches; grayish brown (2.5Y 5/2) silty clay; common fine faint dark grayish brown and few fine distinct dark yellowish brown mottles; weak medium prismatic structure parting to moderate fine and medium angular and subangular blocky; firm, sticky, very plastic; few fine roots; few stress surfaces on peds; few fine and medium black and brown concretions; very strongly acid; clear wavy boundary.
Bg3--29 to 44 inches; grayish brown (2.5Y 5/2) silty clay; common fine prominent strong brown (7.5YR 5/8) and yellowish red (5YR 5/6) mottles; moderate medium prismatic structure parting to moderate fine and medium angular blocky; firm, sticky, very plastic; few fine roots; few stress surfaces on peds; common fine red and few fine black concretions; very strongly acid; gradual wavy boundary.
Bg4--44 to 71 inches; grayish brown (2.5Y 5/2) silty clay; common fine distinct strong brown (7.5YR 5/8) mottles; moderate medium prismatic structure parting to moderate fine and medium angular blocky; firm, sticky, very plastic; few fine roots; few stress surfaces on peds; few fine slickensides that do not intersect; common fine and medium black and red concretions; very strongly acid; gradual wavy boundary. The lower part of the Bg horizon is 50 to more than 60 inches thick.
TYPE LOCATION: Pontotoc County, Mississippi; 6.0 miles west of Pontotoc, on State Highway 6, 0.15 mile west of Mud Creek Bridge and 0.1 mile north into cultivated field, NW1/4NW1/4 sec. 28, T. 9 W., R. 2 E.
RANGE IN CHARACTERISTICS: The solum exceeds 60 inches in thickness. The soil is very strongly acid or strongly acid throughout, except where the surface layer has been limed.
The Ap and A horizons have hue of 10YR, value of 4 or 5, and chroma of 2 or 3; or hue of 2.5Y, value of 4 or 5, and chroma of 2. Some pedons have a very thin A horizon which has hue of 10YR, value of 3, and chroma of 1 or 2. Texture is silty clay loam, silt loam, clay loam, or silty clay. Some pedons have an overwash of material of coarser texture that is less than 10 inches thick.
The Bg1 horizon has hue of 10YR, value of 4 or 5, and chroma of 2 to 4, or it has hue of 2.5Y, value of 4 or 5, and chroma of 2 to 4. Mottles, if present, are few to many in shades of gray, brown, and yellow. The lower part of the Bg horizon has hue of 10YR, or 2.5Y, value of 4 to 7, and chroma of 1 or 2; it has few to many mottles in shades of red, brown, yellow or gray. The Bg horizon is silty clay loam, clay loam, silty clay, or clay. The particle size control section, the 10- to 40-inch section, has from 35 to 55 percent clay. A few patches of oriented clay are in pores and cracks. Black and brown concretions are from few to common throughout.
COMPETING SERIES: There are no competing series in the same family. Closely related soils are the Alligator, Arkabutla, Belden, Houlka, Jackport, Leeper, Marietta, Mathiston, Trinity, Tuscumbia, and Una series. Alligator, Houlka, Leeper, and Tuscumbia shrink and swell appreciably when their moisture content changes and are Vertic Haplaquepts. Also, Alligator and Tuscumbia soils have value of 6 or 7 and chroma of 1 or 2 in more than 60 percent of the matrix in all subhorizons between a depth 10 and 30 inches; Alligator soils are very-fine in the particle size control section; Alligator and Leeper soils have montmorillonitic mineralogy; and Leeper soils are medium acid to moderately alkaline. Arkabutla, Belden, and Mathiston have an organic carbon content that decreases irregularly with depth and are Aeric Fluvaquents; also, they are fine silty in the particle size control section. Jackport soils, which have an argillic horizon and are Vertic Ochraqualfs, are very-fine in the particle size control section and have montmorillonitic mineralogy. Marietta soils are Fluvaquentic Eutrochrepts, and, in addition, they are fine-loamy in the particle size control section, have siliceous mineralogy, and are medium acid to mildly alkaline. Trinity soils are Typic Pelluderts and, in addition, they have a mollic epipedon that is more than 24 inches thick, and they are calcareous.
GEOGRAPHIC SETTING: Urbo soils are on flood plains of streams that drain areas of the Southern Coastal Plain and the Blackland Prairie Major Land Resource Areas. The soils formed in clayey alluvium. These are nearly level to gently sloping soils. Slopes range from 0 to 3 percent. Near the type location the mean annual precipitation is 48 inches and the mean annual temperature is about 62 degrees Fahrenheit.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Arkabutla, Houlka, Mathiston, and Una soils. All of these soils are in similar landscape positions as the Urbo soils, across the nearly linear surfaces of flood plains.
DRAINAGE AND PREMEABILITY: Somewhat poorly drained; slow runoff and very slow permeability. In wet seasons late in winter and early in spring, the water table is at a depth of 1 to 2 feet and most areas of Urbo soils are subject to either occasional or frequent flooding of brief to long duration.
USE AND VEGETATION: Some areas of the Urbo soils are cleared and used for growing cotton, corn, soybeans, and small grains. Wooded areas are in Southern floodplain hardwoods.
DISTRIBUTION AND EXTENT: Alabama, Louisiana, Mississippi, and Texas. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Auburn, Alabama
SERIES ESTABLISHED: Newton 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 9 inches (Ap, A horizons).
Cambic horizon - the zone from approximately 9 to 71 inches (Bg1, Bg2, Bg3, Bg4 horizons).
Aeric Haplaquepts feature - a horizon within the upper 30 inches that has chroma too high for Typic Haplaquepts (Bg1, Bg2, Bg3 horizons).
ADDITIONAL DATA: Highway Test Data for one pedon published in Soil Survey Pontotoc County, Mississippi, issued December 1973, p. 46.