LOCATION NUKRUM             TX

NUKRUM SERIES

The Nukrum series consists of very deep, well drained, slowly permeable soils formed in alkaline clayey alluvium. These soils are on plains and have slopes ranging from 0 to 5 percent.

TAXONOMIC CLASS: Fine, smectitic, thermic Vertic Haplustolls

TYPICAL PEDON: Nukrum silty clay - cropland. (Colors are for dry soil unless otherwise stated.)

Ap--0 to 6 inches; dark grayish brown (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure; hard, firm, slightly sticky; common fine and medium roots; slightly effervescent; moderately alkaline; abrupt smooth boundary. (5 to 9 inches thick)

A--6 to 24 inches; dark grayish brown (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure; hard, firm, sticky; common fine and medium roots; few fine pores; cracks extend to depths greater than 20 inches; strongly effervescent; moderately alkaline; gradual wavy boundary. (10 to 58 inches thick)

Bw--24 to 56 inches; grayish brown (10YR 5/2) silty clay, dark grayish brown (10YR 4/2) moist; moderate medium subangular blocky structure; hard, firm, sticky; few fine roots; few fine pores; few films and threads and masses of calcium carbonate; strongly effervescent; moderately alkaline; gradual wavy boundary. (0 to 32 inches thick)

BCk--56 to 80 inches; brown (10YR 5/3) silty clay loam; brown (10YR 4/3) moist; massive; hard, firm, slightly sticky; 5 percent concretions and masses of calcium carbonate; violently effervescent; moderately alkaline.

TYPE LOCATION: Brown County, Texas; from the Brown County Courthouse, 2.5 miles south on U.S. Highway 377, then 0.7 mile southwest on Chapel Hill Road and 600 feet south of the road in a cultivated field. Latitude: 99 degrees, 00 minutes, and 18 seconds N; longitude: 31 degrees, 40 minutes and 56 seconds W.

RANGE IN CHARACTERISTICS: Solum thickness is greater than 80 inches. The soils, when dry, have cracks 1 to 3 cm wide that extend from the surface to depths more than 20 inches and are open for more than 135 days in most years. The 10- to 40-inch particle-size control section is silty clay, clay, or clay loam containing about 38 to 60 percent clay. Structure of the A and B horizons is subangular blocky or angular blocky. Pressure faces are visible when the soil is moist. The solum contains from 0 to 5 per cent limestone and calcium carbonate fragments. Reaction is slightly to moderately alkaline throughout.

Thickness of the horizons having moist value and chroma of less than 3.5 is 20 to 58 inches. The A horizons have hue of 5YR, 7.5YR or 10YR, value of 3 to 5, and chroma of 2 or 3. The A horizons are silty clay, clay, or clay loam.

The B horizon, where present, has hue of 5YR, 7.5YR or 10YR, value of 4 to 6, chroma of 2 to 4, or is brownish yellow (10YR 6/6). Concretions and powdery masses range from less than 1 percent to about 5 percent by volume. Depth to carbonates ranges from 10 to 26 inches.

The BCk horizon has hue of 5YR, 7.5YR or 10YR, value of 4 to 7, chroma of 2 to 6, or is pale red (2.5YR 6/2) or light brownish gray (2.5Y 6/2). Texture is silty clay loam, clay loam, silty clay, or clay. Calcium carbonate equivalent ranges from 15 to 30 percent. Visible calcium carbonate in the form of concretions, pebbles or powdery masses range from 5 to 20 percent.

COMPETING SERIES: There are no competing series in the same family. Similar soils are the Garvin, Knippa, Krum, Lewisville, Matoy, and Rowena series. Garvin soils are moist in the soil moisture control section for longer periods, contain exchangeable sodium within the control section, and have an irregular decrease in organic matter with depth. Knippa and Rowena soils have calcic horizons at depths of less than 40 inches and have mixed mineralogy. Krum soils are moist in the soil moisture control section for longer periods. Lewisville soils, when dry, have cracks that are less than 1 cm. wide, have mollic epipedons less than 20 inches thick and have mixed mineralogy. Matoy soils have a lithic contact with limestone between 20 and 40 inches.

GEOGRAPHIC SETTING: Nukrum soils are in nearly level to gently sloping plains in filled valleys. Slope gradients range from 0 to 5 percent. The soil formed in thick beds of unconsolidated calcareous, clayey sediments from shaly clay of Pennsylvanian or Permian age. Mean annual precipitation ranges from 25 to 29 inches, and mean annual temperature ranges from 63 to 67 degrees F. Frost free days range from 220 to 240 days, and elevation ranges from 1,150 to 1,950 feet. Thornthwaite P-E indices are 34 to 44.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Rowena series, and the Frio, Leeray, Nuvalde, and Throck series. Frio, Nuvalde, and Throck soils, when dry, do not have cracks as wide as 1 cm at 20 inches depth. Leeray soils have intersecting slickensides and gilgai microrelief.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is slow. Runoff is low on slopes less than 1 percent and medium on 1 to 5 percent slopes.

USE AND VEGETATION: Used for cropland, pastureland, and range. Small grains, forage sorghums, and grain sorghums are the main crops. Coastal bermudagrass and Kleingrass are the main pasture grasses. Native vegetation is mostly sideoats grama, Texas wintergrass, buffalograss, pricklypear, mesquite, and liveoak.

DISTRIBUTION AND EXTENT: Rolling Limestone Prairies and North Central Prairie of Texas. The series is moderately extensive.

MLRA OFFICE RESPONSIBLE: Temple, Texas

SERIES ESTABLISHED: Brown County, Texas; 1975.

REMARKS: Classification change from mixed mineralogy to smectitic mineralogy based on Texas A&M University laboratory samples from the series type location in Brown County and from type locations in Callahan and Mason Counties, Texas.

The Nukrum series was formerly included in the Krum, or Rowena series.

Diagnostic horizons and features recognized in this pedon are:

Mollic epipedon - 0 to 24 inches. (Ap and A1 horizons)

Cambic horizon - 24 to 56 inches. (Bw horizon). It is absent in some pedons.

Vertic feature - the occurrence of dry weather cracks from 1 to 3 cm wide that extend from the surface to more than 20 inches depth. The particle-size control section has 38 to 60 percent clay.

Calcic horizon - 56 to 72 inches. (BCk horizon)