LOCATION WILLOW OKTentative Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, thermic Typic Argiustolls
TYPICAL PEDON: Willow loam--on a 1 percent slope in cropland. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 7 inches; brown (7.5YR 4/2) loam, dark brown (7.5YR 3/2), moist; moderate fine and medium granular structure; very friable, hard; common fine and very fine roots; 1 percent quartz gravels; noneffervescent; slightly acid, pH 6.5; abrupt smooth boundary. (6 to 16 inches thick.)
Bt1--7 to 17 inches; reddish brown (5YR 4/3) clay loam, dark reddish brown (5YR 3/3), moist; weak medium prismatic structure parting to moderate fine and medium subangular blocky; friable, very hard; few fine and very fine roots; common fine and very fine pores; many distinct clay films on all faces of peds; 1 percent quartz gravels; noneffervescent; slightly acid, pH 6.5; gradual smooth boundary.
Bt2--17 to 25 inches); reddish brown (5YR 5/4) clay loam, reddish brown (5YR 4/4), moist; weak medium prismatic structure parting to moderate fine and medium subangular blocky; friable, very hard; few fine and very fine roots; common fine and very fine pores; common distinct clay films on all faces of peds; 1 percent quartz gravels; noneffervescent; neutral, pH 7.0; gradual smooth boundary.
Btk--25 to 31 inches; yellowish red (5YR 5/6) clay loam, yellowish red (5YR 4/6), moist; weak medium prismatic structure parting to moderate fine and medium subangular blocky; friable, hard; few fine and very fine roots; common fine and very fine pores; few faint clay films on vertical faces of peds; 3 percent fine and medium masses and threads of calcium carbonate; 1 percent quartz gravels and 1 percent paragravel of sandstone; strongly effervescent; moderately alkaline, pH 8.0; clear wavy boundary. (Combined thickness of the Bt horizons is 18 to 38 inches.)
2Bk--31 to 39 inches; reddish yellow (5YR 6/6) loam, yellowish red (5YR 5/6), moist; weak coarse prismatic structure parting to weak fine and medium subangular blocky; friable, very hard; few fine and very fine roots; many fine and very fine and few medium pores; 5 percent fine and medium masses of calcium carbonate; 4 percent paragravels of sandstone; strongly effervescent; moderately alkaline, pH 8.0; gradual wavy boundary. (0 to 15 inches thick)
2BCk--39 to 54 inches; yellowish red (5YR 5/6) loam, yellowish red (5YR 4/6), moist; weak coarse prismatic structure parting to weak medium subangular blocky; friable, very hard; few fine and very fine roots; many fine and very fine and few medium pores; 1 percent fine masses of iron-manganese; 2 percent masses of calcium carbonate; 5 percent noncemented sandstone fragments and 5 percent paragravel of sandstone; strongly effervescent; moderately alkaline, pH 8.0; gradual wavy boundary. (8 to 15 inches thick)
2Cd--54 to 80 inches; pale yellow (2.5Y 7/3) noncemented sandstone bedrock that slakes to loam, light yellowish brown (2.5Y 6/3), moist; slightly effervescent; moderately alkaline.
TYPE LOCATION: Greer County, Oklahoma; from the intersection of U.S. Highway 283 and OK State Highway 34 in Mangum; about 7 miles north on U.S. Highway 283and 7.55 miles west on county road; 225 feet south in cultivated field. (located about 225 feet south and 2400 feet east of the northwest corner of section 28, T. 6 N., R. 23 W.); Latitude: 34 degrees, 58 minutes, 21.20 seconds N; Longitude: 99 degrees, 38 minutes, 7.07 seconds W.; Reed, OK topographic quadrangle; NAD 1927.
RANGE IN CHARACTERISTICS:
Thickness of the mollic epipedon, 7 to 18 inches (10 to 18 inches thick in pedons that have secondary calcium carbonate at a depth of more than 30 inches)
Depth to secondary calcium carbonate: 15 to 36 inches
Depth to calcic horizon (where present): 28 to 52 inches
Depth to lithologic discontinuity: 25 to 52 inches
Depth to densic bedrock: 40 to 60 inches
Particle-size control section (weighted average)
Clay content: 18 to 35 percent
Total sand content: 15 to 50 percent
Fine sand or coarser content: less than 15 percent
CEC/clay ratio: more than 0.6
A Horizon
Hue: 5YR or 7.5YR
Value: 4 (3 moist)
Chroma: 2 or 3
Texture: Loam, silt loam, or clay loam
Clay content: 18 to 30 percent
Coarse fragments: 0 to 2 percent rounded siliceous gravel
Effervescence: Noneffervescent to very slightly effervescent
Reaction: Slightly acid to slightly alkaline (pH 6.1 - 7.8)
Bt and Btk (where present) Horizons
Hue: 5YR or 7.5YR
Value: 4 or 5 (3 or 4 moist)
Chroma: 3 to 6
Texture: Clay loam, silty clay loam, loam, or silt loam
Clay content: 25 to 38 percent
Coarse fragments: 0 to 2 percent rounded siliceous gravels
Calcium carbonate equivalent: 0 to 10 percent
Identifiable secondary carbonate: 0 to 5 percent, fine and medium, concretions and/or masses
Effervescence: Noneffervescent to strongly effervescent
Reaction: Neutral to moderately alkaline (pH 6.6 - 8.4)
Bk Horizon (where present)
Hue: 5YR or 7.5YR
Value: 5 or 6 (4 or 5 moist)
Chroma: 4 or 6
Texture: Loam, silt loam, or clay loam
Clay content: 18 to 30 percent
Pararock fragments: 0 to 5 percent paragravel of sandstone
Calcium carbonate equivalent: 10 to 40 percent
Identifiable secondary carbonate: 3 to 30 percent, fine to coarse, concretions, films, and/or masses
EC (dS/m): 0 to 4
Gypsum: 0 to 2 percent
SAR: 0 to 4
Effervescence: Strongly effervescent to violently effervescent
Reaction: Moderately alkaline or strongly alkaline (pH 7.9 to 9.0)
BCk Horizon
Hue: 5YR to 10YR
Value: 5 to 7 (4 to 6 moist)
Chroma: 4 to 8
Texture: Loam, silt loam, or very fine sandy loam
Clay content: 10 to 20 percent
Pararock fragments: 0 to 15 percent paragravel of sandstone
Calcium carbonate equivalent: 10 to 25 percent
Identifiable secondary carbonate: 2 to 20 percent, fine and medium, concretions, films, and/or masses
EC (dS/m): 0 to 8
Gypsum: 0 to 5 percent
SAR: 0 to 8
Effervescence: Slightly effervescent to violently effervescent
Reaction: Moderately alkaline or strongly alkaline (pH 7.9 to 9.0)
Cd Horizon
Hue: 2.5YR to 5Y
Value: 5 to 8 (4 to 7 moist)
Chroma: 1 to 6
Texture: interbedded layers of red to white sandstone bedrock with a few layers of red siltstone
Cementation: Mostly noncemented with few thin layers of extremely to weakly cemented which increase with depth
Excavation difficulty: Moderate to high
Effervescence: Noneffervescent to slightly effervescent
Reaction: Moderately alkaline or strongly alkaline (pH 7.9 to 9.0)
COMPETING SERIES: These are the
Carey and
Selman series.
Carey and Selman: These soils are more than 60 inches deep to bedrock and do not have a calcic horizon.
GEOGRAPHIC SETTING:
Parent material: Loamy alluvium and pedisediments over Permian age sandstones mainly of the Duncan/San Angelo, Brinkman, Hennessey, and Clear Fork Formations
Landform: Plain terraces and footslopes and toeslopes of pediments
Slope: 0 to 3 percent
Mean annual air temperature range: 60 to 64 degrees F.
Mean annual precipitation range: 24 to 28 inches
Frost-free period: 210 to 230 days
Elevation: 1100 to 1700 feet
Thornthwaite annual P-E indices: 32 to 44
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Burford,
Gotebo,
Roark, and
Westill series.
Burford: These soils do not have a mollic epipedon or an argillic horizon.
Gotebo: These soils do not have a mollic epipedon and are less than 40 inches deep to bedrock.
Roark: These soils have a mollic epipedon more than 20 inches thick and do not have bedrock within 60 inches of the surface.
Westill: These soils have a fine textured particle-size control section.
DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderately slow. Runoff is low on 0 to 1 percent slopes and medium on 1 to 3 percent slopes.
USE AND VEGETATION: The major use of these soils is crop production with a lesser amount used for livestock grazing. The major crops are wheat and cotton. Native vegetation is a mixture of tall, mid, and short grasses, mainly little bluestem, sideoats grama, blue grama, sand bluestem, yellow Indiangrass, switchgrass, buffalograss, and other perennial grasses and forbs.
DISTRIBUTION AND EXTENT: Central Rolling Red Plains of western Oklahoma and Texas; LRR H; MLRA 78C; Moderate extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES PROPOSED: Greer County, Oklahoma; 2001. The name comes from a small town in the county.
REMARKS: These soils were formerly mapped as St. Paul silt loam, 1 to 3 percent slopes in the soil survey of Greer County, OK, issued 1967.
Diagnostic horizons and features recognized in this pedon are:
Particle size control section: 7 to 27 inches. (Bt1,2, and Btk horizons)
Mollic epipedon: 0 to 17 inches. (A and Bt1 horizons)
Argillic horizon: 7 to 31 inches. (Bt and Btk horizons)
Calcic horizon: 31 to 39 inches. (2Bk horizon)
Densic bedrock: The contact with sandstone at 54 inches. (2Cd horizon)
Lithologic discontinuity: At the upper boundary of the 2Bk horizon. (31 inches)
Additional Comments: The assignment of the cation-exchange activity class is supported by laboratory data number (S00OK-055-001) from Greer County, Oklahoma.
Range Site: Limy Prairie (078CY057OK)
ADDITIONAL DATA: NSSL data from type location in Greer County, Oklahoma (S00OK-055-001) and similar soils sampled as Tillman variant: (S82TX-207-002), (S82TX-207-003), and (S82TX-207-004) from Haskell County, Texas.
TAXONOMIC VERSION: Keys to Soil Taxonomy, Ninth Edition, 2003.