LOCATION LAWTON OKEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Typic Argiustolls
TYPICAL PEDON: Lawton loam--rangeland. (Colors are for dry soil unless otherwise stated.)
A1--0 to 11 inches; brown (7.5YR 4/2) loam, dark brown (7.5YR 3/2) moist; moderate medium granular structure; hard, friable; few fine pebbles; slightly acid; clear smooth boundary. (6 to 12 inches thick)
BA--11 to 18 inches; reddish brown (5YR 4/3) clay loam, dark reddish brown (5YR 3/3) moist; weak medium granular structure; hard, friable; few fine pebbles; neutral; gradual smooth boundary. (4 to 8 inches thick)
Bt1--18 to 32 inches; reddish brown (5YR 4/4) clay loam, dark reddish brown (5YR 3/4) moist; moderate medium blocky structure; very hard, firm; nearly continuous clay films on faces of peds; many coarse sand grains and few pebbles; neutral; gradual smooth boundary. (14 to 35 inches thick)
Bt2--32 to 47 inches; reddish brown (5YR 5/4) clay loam, reddish brown (5YR 4/4) moist; weak medium blocky structure; very hard, firm; patchy clay films on faces of peds; many medium sand grains and few fine pebbles; neutral; gradual smooth boundary. (10 to 30 inches thick)
BC--47 to 72 inches; yellowish red (5YR 5/6) sandy clay loam, yellowish red (5YR 4/6) moist; weak medium blocky structure; hard, friable; many medium sand grains and few fine pebbles; slightly alkaline.
TYPE LOCATION: Comanche County, Oklahoma; about 1/2 mile southwest of Faxon; 1,600 feet north and 100 feet east of southwest corner of sec. 20, T. 1 S., R. 13 W.
RANGE IN CHARACTERISTICS:
Particle-size control section (weighted average)
Clay content: 35 to 40 percent
Coarse Fragments: 1 to 15 percent
CEC/clay ratio: more than 0.6
Depth to secondary calcium carbonate: Some pedons contain a few secondary carbonates below 30 inches
Thickness of the mollic epipedon, 10 to 20 inches
A Horizon
Hue: 5YR to 10YR
Value: 3 to 5 (2 or 3 moist)
Chroma: 2 or 3
Texture: Loam or silt loam
Clay content: 18 to 27 percent
Coarse fragments, by volume: 2mm to 3 inches in diameter range from 1 to 10 percent; more than 3 inches in diameter range from 0 to 5 percent
Effervescence: Noneffervescent
Reaction: Slightly acid or neutral
BA Horizon (where present)
Hue: 5YR to 10YR
Value: 3 to 5 (2 or 3 moist)
Chroma: 2 or 3
Texture: Loam or clay loam
Clay content: 20 to 35 percent
Coarse fragments, by volume: 2mm to 3 inches in diameter range from 1 to 10 percent
Effervescence: Noneffervescent
Reaction: Slightly acid or neutral
Upper Bt Horizon
Hue: 2.5YR to 7.5YR
Value: 4 to 6 (3 to 5 moist)
Chroma: 4 or 6
Texture: Clay loam
Clay content: 35 to 40 percent
Coarse fragments, by volume: 2mm to 3 inches in diameter range from 1 to 10 percent
Calcium carbonate equivalent: 0 to 0 percent
EC (dS/m): 0 to 0
Gypsum: 0 to 0 percent
SAR: 0 to 2
Effervescence: Noneffervescent
Reaction: Slightly acid to moderately alkaline
Lower Bt Horizon
Hue: 2.5YR to 7.5YR
Value: 4 to 6 (3 to 5 moist)
Chroma: 4 or 6
Texture: Clay loam, loam, or clay and their gravelly counterparts
Clay content: 25 to 50 percent
Coarse fragments, by volume: 2mm to 3 inches in diameter average from 1 to 35 percent, but some thin layers may contain up to 50 percent
Identifiable secondary carbonate: some pedons may have a few concretions, films, threads, or masses
Calcium carbonate equivalent: 0 to 5 percent
EC (dS/m): 0 to 2
Gypsum: 0 to 1 percent
SAR: 0 to 6
Effervescence: Noneffervescent to slightly effervescent
Reaction: Neutral to moderately alkaline
BC Horizon
Hue: 2.5YR to 7.5YR
Value: 4 to 6 (3 to 5 moist)
Chroma: 4 or 6
Texture: Clay loam, loam, or sandy clay loam and their gravelly counterparts
Clay content: 18 to 40 percent
Coarse fragments, by volume: 2mm to 3 inches in diameter average from 1 to 35 percent, but some thin layers may contain up to 50 percent
Identifiable secondary carbonate: some pedons may have a few concretions, films, threads, or masses
Calcium carbonate equivalent: 0 to 10 percent
EC (dS/m): 0 to 2
Gypsum: 0 to 2 percent
SAR: 0 to 6
Effervescence: Noneffervescent to strongly effervescent
Reaction: Neutral to moderately alkaline
COMPETING SERIES: These are the
Bexar,
Frankirk,
La Casa,
Luckenbach,
Rowden,
Sagerton, and
Swenson series. None of these soils contain granitic gravels.
Bexar, Rowden, and Swenson: These soils are 20 to 40 inches deep over limestone bedrock.
Frankirk: These soils have secondary carbonate between 29 and 48 inches and do not allow gravelly textures.
La Casa, Luckenbach, and Sagerton: These soils have secondary carbonates within 30 inches of the surface. In addition, La Casa and Sagerton soils contain a calcic horizon.
GEOGRAPHIC SETTING:
Parent material: Loamy alluvium that contains variable amounts of gravel derived from granite and associated mixed rocks.
Landform: Treads and risers of stream terraces that drain away from the Wichita Mountains and alluvial fans of the Wichita Mountains.
Slope: 0 to 8 percent
Mean annual air temperature range: 60 to 64 degrees F.
Mean annual precipitation range: 25 to 32 inches
Frost-free period: 205 to 230 days
Elevation: 1000 to 1800 feet
Thornthwaite annual P-E indices: 38 to 50
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Brico,
Foard,
Hollister,
Tillman, and
Vernon series.
Brico: These soils occur on higher areas adjacent to the
Wichita Mountains and are clayey-skeletal in the particle-size control section.
Foard and Hollister: These soils occur on slightly lower areas, have smectitic mineralogy and vertic properties. In addition, Foard soils contain a natric horizon.
Tillman: These soils occur on lower areas, do not decrease in clay content within 60 inches, and do not contain gravelly textures.
Vernon: These soils occur on higher and lower side slopes and are 20 to 40 inches deep over Permian age shale or claystone bedrock.
DRAINAGE AND PERMEABILITY: Well drained. moderately slow permeability. Runoff is low on less than 1 percent slopes, medium on 1 to 5 percent slopes, and high on 5 to 8 percent slopes.
USE AND VEGETATION: Most areas are used for wheat or other small grains. Some areas are in cotton, sorghums and alfalfa. Native vegetation consists of tall and mid grasses.
DISTRIBUTION AND EXTENT: Southwestern Oklahoma; MLRA 82B Wichita Mountains; Moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Comanche County, Oklahoma; 1941.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from the soil surface to a depth of 18 inches. (the A and BA horizons)
Argillic horizon - the zone from 18 to 47 inches. (the Bt horizon)