Established Series


The Mangum series consists of very deep, well drained, very slowly permeable soils that formed in calcareous clayey alluvium. These soils are on nearly level flood plains of major streams of the Central Rolling Red Plains (MLRA-78) and North Central Prairies (MLRA-80B). Slopes range from 0 to 1 percent.

TAXONOMIC CLASS: Fine, mixed, active, thermic Vertic Haplustepts

TYPICAL PEDON: Mangum clay--pasture. (Colors are for dry soil unless otherwise stated.)

A--0 to 7 inches; reddish brown (5YR 5/4) clay, reddish brown (5YR 4/4) moist; moderate fine and medium blocky structure; very hard, firm, sticky; few grass roots; few very fine pores; calcareous; moderately alkaline; clear smooth boundary. (5 to 16 inches thick)

Bw-7 to 24 inches; reddish brown (5YR 5/4) clay, reddish brown (5YR 4/4) moist; moderate fine and medium angular blocky structure; extremely hard, very firm, sticky; few fine roots; few very fine pores; cracks 1 to 1-1/2 cm wide extend from top to bottom of this horizon; calcareous; moderately alkaline; abrupt smooth boundary. (8 to 36 inches thick)

C1--24 to 48 inches; red (2.5YR 4/6) clay, dark red (2.5YR 3/6) moist; massive; extremely hard, very firm, sticky; few fine pores; evident bedding planes; few dark vertical streaks along cracks; few fine calcium carbonate concretions in lower part; calcareous, moderately alkaline; gradual smooth boundary. (0 to 30 inches thick)

C2--48 to 80 inches; red (2.5YR 5/6) silty clay, red (2.5YR 4/6) moist; massive; very hard, very firm, sticky; few fine calcium carbonate concretions and films and threads of secondary calcium carbonates; bedding planes in lower part; calcareous; moderately alkaline.

TYPE LOCATION: Scurry County, Texas; 15-1/2 airline miles southwest of Snyder; in the flood plain of the Colorado River; in a pasture 25 feet west of a county road from a point 0.33 mile north of the Colorado River Bridge below the dam of the Lake J. B. Thomas.

RANGE IN CHARACTERISTICS: These soils are calcareous throughout. The texture in the 10- to 40-inch control section is silty clay loam, clay loam, silty clay or clay with clay content ranging from 35 to 60 percent. Partially decomposed leaves are along some vertical cracks, and thin strata and lenses of silty clay loam and silt loam are in some pedons. Some pedons contain buried dark A horizons at depths of 20 to 40 inches that have blocky and subangular blocky structure.

The A horizon is reddish brown (5YR 4/3, 4/4, 5/3, 5/4; 2.5YR 5/4, 4/4), light reddish brown (5YR 6/4), red (2.5YR 4/6, 5/6), yellowish red (5YR 4/6, 5/6), or brown (7.5YR 4/2, 4/4, 5/2, 5/4). It is clay, silty clay, silty clay loam, or silt loam. If the A horizon is 10 or more inches thick, moist color value or chroma are 3.5 or more.

The B and C horizons are light reddish brown (2.5YR 6/4; 5YR 6/4), reddish brown (2.5YR 4/4, 5/4; 5YR 4/3, 4/4, 5/4), light red (2.5YR 6/6), red (2.5YR 4/6, 5/6), reddish yellow (5YR 6/6), or yellowish red (5YR 4/6, 5/6). The C horizon contains few to common films, threads, and concretions of calcium carbonate. Electrical conductivity increases with depth ranging from less than 2 mmhos in the surface to 8 mmhos at depths greater than 60 inches.

COMPETING SERIES: This is the Throck series. Closely related series include the Chargo, Denhawken, Ellis, Miller, Montoya, Navajo, Padgett, Stamford, and Treadway series. Throck soils have shale at depths of less than 60 inches. Chargo and Denhawken soils have average annual soil temperature of more than 72 degrees F. Ellis soils are moist for longer periods and lack stratification. Miller soils have mollic epipedons. Montoya soils are usually dry. Navajo soils have average annual soil temperature of less than 59 degrees F. Stamford soils have intersecting slickensides, and parallelepipeds which are tilted 10 degrees to 60 degrees from the horizontal. Treadway soils have a conductivity greater than 2 mmhos at depths less than 40 inches. Padgett soils have intersecting slickensides.

GEOGRAPHIC SETTING: Mangum soils are on nearly level flood plains than overflow about once or twice a year to once every 20 years. The soils formed in clayey sediments several feet thick washed largely from clayey soils formed in Permian or Triassic red beds. Average annual precipitation from 19 to 32 inches, and mean annual temperature from 57 degrees to 68 degrees F. Frost free period is 185 to 240 days and elevation ranges from 1000 to 2500 feet. Thornthwaite annual P-E indices range from 28 to 44.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Beckman, Clairemont, Colorado, Gageby, Spur, Treadway and Weswood series. Beckman soils lack cambic horizons and have fluventic properties. The Clairmont, Colorado, Gageby, Spur, and Weswood soils have formed in less clayey alluvial sediments than Mangum soils and have less than 35 percent clay in the control section. Treadway soils have conductivity greater than 2 mmhos at depths less than 40 inches and occur on higher landscape positions.

DRAINAGE AND PERMEABILITY: Mangum soils are well drained; Runoff is high, permeability is very slow. Water enters the soil rapidly when the soil is dry and cracks, but after the cracks are closed water movement into the soil is very slow.

USE AND VEGETATION: Dominantly used for range but a few areas are cultivated to wheat and grain sorghum. Buffalograss and tobosa grass are the dominant grasses, and mesquite brush is the prevalent invader.

DISTRIBUTION AND EXTENT: Central Rolling Red Plains (MLRA 78) of Texas, Oklahoma and Kansas. The series is of moderate extent.


SERIES ESTABLISHED: Greer County, Oklahoma; 1965.

REMARKS: The soils now placed in the Mangum series were included in the Miller series.

Diagnostic horizons and features in this pedon are:

Ochric epipedon - 0 to 7 inches (A horizon)

Cambic horizon - 7 to 24 inches (Bw horizon)

High shrink-swell properties - cracks in the A, Bw and C1 horizons.

National Cooperative Soil Survey