LOCATION COTTONWOOD         TX+OK

COTTONWOOD SERIES

TAXONOMIC CLASS: Loamy, mixed, superactive, calcareous, thermic Lithic Ustorthents

TYPICAL PEDON: Cottonwood silt loam, on a northeast facing, 3 percent slope in rangeland at an elevation of 503 m (1,650 ft). (Colors are for dry soil unless otherwise stated.)

A1--0 to 13 cm (0 to 5 in); light brown (7.5YR 6/3) loam, brown (7.5YR 4/3) moist; moderate medium granular structure; soft; very friable; common fine and medium roots; common fine pores; strongly effervescent; moderately alkaline; clear smooth boundary.

A2--13 to 31 cm (5 to 12 in); light brown (7.5YR 6/4) loam, brown (7.5YR 4/4) moist; moderate fine subangular blocky structure; soft, very friable; common fine and medium roots; common fine pores; strongly effervescent; moderately alkaline; clear wavy boundary. (Combined thickness is 7 to 36 cm [3 to 14 in].)

Cr--31 to 48 cm (12 to 19 in); very pale brown (10YR 8/2) slightly weathered, weakly cemented gypsum bedrock; massive; few fine roots in fractures; slightly effervescent, moderately alkaline; gradual wavy boundary. (Thickness is 0 to 13 cm thick [0 to 5 in].)

R--48 to 56 cm (19 to 22 in); very pale brown (10YR 8/2) strongly cemented gypsum bedrock; massive; no roots; neutral.

TYPE LOCATION: King County, Texas; From the courthouse in Guthrie, 13.5 miles north on U.S. Highway 83, 3.2 miles east on Farm Road 1168, 3.0 miles east on Farm Road 3416, 9.7 miles southeast and east on ranch road, 1.1 miles north on ranch road, and 200 feet east in rangeland. Latitude: 33 degrees, 48 minutes, 5 seconds N; Longitude: 100 degrees, 5 minutes, 24 seconds W; Lowrance Mountain USGS topographic quadrangle; NAD 1983.

RANGE IN CHARACTERISTICS:

Soil moisture: An ustic soil moisture regime. The soil moisture control section is dry in some or all parts for more than 90 but less than 150 cumulative days in normal years. June through August and December through February are the driest months. These soils are intermittently moist in September through November and March through May.

Mean annual soil temperature: 15 to 17.8 degrees C (59 to 64 degrees F)
Depth to lithic contact: 7 to 48 cm (3 to 19 in)
Depth to paralithic contact: 7 to 38 cm (3 to 15 in)

Particle-size control section (weighted average)
Clay content: 18 to 35 percent
Coarse Fragments: 0 to 3 percent
CEC/clay ratio: 0.6 or more

A horizon
Hue: 5YR to 10YR
Value: 5 to 7
Chroma: 2 to 6
Texture: loam, silt loam, clay loam, or silty clay loam
Clay content: 18 to 35 percent
Calcium carbonate equivalent: 3 to 30 percent
EC (dS/m): 0 to 2
Gypsum: 5 to 40 percent
SAR: 0 to 4
Effervescence: slightly effervescent to violently effervescent
Reaction: moderately alkaline

Cy horizon (where present)
Hue: 7.5YR to 5Y
Value: 5 to 8
Chroma: 1 to 6
Texture: gypsiferous silt loam, gypsiferous loam, gypsiferous silty clay loam, or gypsiferous clay loam
Calcium carbonate equivalent: 3 to 30 percent
EC (dS/m): 0 to 4
Gypsum: 40 to 90 percent
SAR: 0 to 4
Effervescence: slightly effervescent to violently effervescent
Reaction: moderately alkaline

Cr horizon
Hue: 7.5YR to 5Y
Value: 6 to 8
Chroma: 1 to 6
Texture: extremely weakly to moderately cemented gypsum bedrock

R horizon
This horizon consists of massive crystalline gypsum or alabaster bedrock 1.5 m to 5 m (5 to 15 ft) thick that is strongly to very strongly cemented. The gypsum is interbedded with reddish-brown mudstone and thin layers of dolomite and greenish-gray mudstone. The upper boundary of the R horizon is a lithic contact and is root restrictive. This material has very high to extremely high excavation difficulty.

COMPETING SERIES: There are no series in the same family. Similar soils are the Burson, Cornick, Harmon, Knoco, and Spikebox series.
Burson soils: are very shallow to soft sandstone.
Cornick soils: have a mollic epipedon.
Harmon soils: are loamy-skeletal in the particle-size control section and have carbonatic mineralogy.
Knoco soils: are clayey in the particle-size control section and are formed from reddish-brown mudstone.
Spikebox soils: are formed from soft sandstone.

GEOGRAPHIC SETTING:
Parent material: loamy residuum overlying massive gypsum bedrock, which is mostly alabaster, of the Blaine Formation of Permian age.
Landform: summits and side slopes of hills and ridges
Slope: ranges from 1 to 45 percent, but is mainly less than 20 percent
Mean annual air temperature range: 13.8 to 17.8 degrees C (57 to 64 degrees F)
Mean annual precipitation range: 53 to 26 cm (21 to 26 in)
Frost-free period: 180 to 230 days
Elevation: 426 to 732 m (1,400 to 2,400 ft)
Thornthwaite annual P-E indices: 32 to 40

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Aspermont, Harmon, Knoco, La Casa, Nipsum, Quanah, Talpa, and Vinson series.
Aspermont soils: are deep to Permian redbed sediments and are on slightly lower side slopes.
Harmon and Talpa soils: are formed from dolomite limestone on similar positions.
Knoco soils: are formed from reddish mudstone on similar positions.
La Casa, Nipsum, and Quanah soils: have a mollic epipedon, are very deep to bedrock, and are on lower foot slopes.
Vinson soils: have a mollic epipedon, are moderately deep to gypsum beds, and are on slightly lower side slopes.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate in the solum and very slow in the gypsum bedrock. Runoff is high on less than 1 percent slopes, and very high on slopes more than 1 percent.

USE AND VEGETATION: Used primarily for livestock grazing. Cover is sparse short grasses where grazing is continuous, but some tall grasses grow in protected areas. Where the soil is intermingled with deeper and more productive soils, small areas are cultivated. Ecological site is Gyp (078BY076TX and 078CY038OK).

DISTRIBUTION AND EXTENT: Rolling Red Plains, Western Part (LRR H; MLRA 78B) of northwest Texas and southwest Oklahoma; The series is of large extent.

MLRA OFFICE RESPONSIBLE: Temple, Texas.

SERIES ESTABLISHED: Childress County, Texas; 1910 in the Reconnaissance Survey of the Panhandle Region, Texas.

REMARKS: The original series concept included soils that are shallow to a paralithic contact with massive gypsum bedrock and soils that have a gypsic horizon mapped in a complex with the Acme series. In 1999, the series concept was revised and restricted to shallow or very shallow to massive gypsum bedrock on upland positions. This revision retains the Cottonwood series with the largest acreage of these soils. The soils mapped in lacustrine sediments that have a gypsic horizon, on nearly level to very gently sloping positions, in a complex with Acme soils will be included with the Childress series.
Diagnostic horizons and features recognized in this pedon are:

Particle size control section: 0 to 31 cm (0 to 12 in) (A horizons).
Ochric epipedon: 0 to 31 cm (0 to 12 in) (A horizons).
Paralithic contact: The contact with weakly cemented gypsum bedrock is at 31 cm (12 in). (Cr horizon)
Lithic contact: The contact with strongly cemented gypsum bedrock is at 48 cm (19 in). (R horizon).

ADDITIONAL DATA: none

TAXONOMIC VERSION: Soil Taxonomy, Tenth Edition, 2006.