LOCATION SEVERN OK+AR LA TXEstablished Series
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, calcareous, thermic Typic Udifluvents
TYPICAL PEDON: Severn very fine sandy loam, in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 10 inches; reddish brown (5YR 4/3) very fine sandy loam; weak medium and fine granular structure; very friable; few fine roots; calcareous, moderately alkaline; gradual smooth boundary. (0 to 16 inches thick)
C1--10 to 27 inches; reddish brown (5YR 4/4) very fine sandy loam; massive; very friable; few fine roots; few fine pores; common thin strata of loam and silt loam; calcareous, moderately alkaline; clear smooth boundary. (10 to 35 inches thick)
C2--27 to 40 inches; reddish brown (5YR 5/4) very fine sandy loam; massive; very friable; few fine pores; common thin strata of silt loam and loam; calcareous, moderately alkaline; clear smooth boundary. (0 to 20 inches thick)
C3--40 to 65 inches; reddish brown (5YR 4/4) very fine sandy loam; massive; very friable; few fine and medium pores; thin patchy white coats; few thin strata of loam and loamy fine sand; calcareous, moderately alkaline.
TYPE LOCATION: McCurtain County, Oklahoma; about 6 miles south of Idabel, Oklahoma; 500 feet east and 200 feet north of the southwest corner of sec. 34, T. 8 S., R. 23 E.
RANGE IN CHARACTERISTICS: These soils are calcareous in all horizons below 10 inches and are calcareous to noncalcareous to the surface.
The A horizon has hue of 5YR or 7.5YR, value of 3 to 5, and chroma of 2 to 4. It is very fine sandy loam, fine sandy loam, loam, silt loam, or silty clay loam and is slightly or moderately alkaline.
The C horizon has hue of 7.5 YR, value of 4, 5, or 6, and chroma of 4 to 8 or hue of 5YR, value of 3 to 6, and chroma of 3 to 8, or hue of 2.5YR, value of 3 to 5, and chroma of 4. It is stratified very fine sandy loam, silt loam, or loamy very fine sand. Within the control section, the cumulative thickness of layers containing more than 18 percent clay is less than 8 inches.
Buried horizons are common below a depth of 24 inches. Colors and textures are similar to the A and C horizons.
COMPETING SERIES: These are no other series in this family.
GEOGRAPHIC SETTING: Severn soils occur on level to gently undulating flood plains that carry sediments mainly from Permian Red Beds. They formed in loamy and silty calcareous alluvium. Slopes are 0 to 6 percent. Average annual precipitation ranges from 38 to 52 inches. Mean annual temperature ranges from 59 degrees to 65 degrees F. The Thornthwaite annual P-E indices are 64 to 80. They are rarely flooded in protected areas or commonly flooded for very brief or brief periods during January though October. Average frost free days range from 210 to 240. Elevation ranges from 100 to 800 feet.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Choska, Kiomatia, Oklared, Coushatta, Idabel, Redlake, and Roebuck series. The Choska, Coushatta, Idabel and Oklared soils are at similar elevations. Kiomatia soils are in lower areas. Redlake soils are further from the streams. Roebuck soils are in back slough positions. All of these soils have a cambic horizon except the Oklared series. Coushatta soils contain more than 18 percent clay in the control section. Idabel soils contain more than 15 percent sand coarser than very fine sand in the control section. Redlake and Roebuck soils contain more than 35 percent clay in the control section. In addition, Roebuck soils have a mollic epipedon.
DRAINAGE AND PERMEABILITY: Well drained; negligible to low runoff; moderately rapid permeability.
USE AND VEGETATION: Most areas have been cleared and are used for growing tame pasture, cotton, grain sorghums, soybeans, and alfalfa. Native vegetation is cottonwood, sycamore, hackberry, and pecan with an understory of grasses.
DISTRIBUTION AND EXTENT: Southeastern Oklahoma, Arkansas, Louisiana, and Texas. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: McCurtain County, Oklahoma; 1970.
REMARKS: Soil Interpretative Record No. OK0088
Diagnostic horizons and features in the soil are:
Ochric epipedon is 0 to 10 inches. Stratified layers are within a depth of 40 inches from the soil surface.
The Udic moisture regime control section is dry in some part less than 90 cumulative days. This pedon is calcareous in all parts below a depth of 10 inches.