Established Series


The Colorado series consists of very deep, well drained, moderately permeable soils that formed in calcareous loamy alluvium. These nearly level soils occur on flood plains. Slope ranges from 0 to 1 percent. Mean annual precipitation is about 584 mm (23 in) and the mean annual air temperature is about 17.8 degrees C (64 degrees F).

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, calcareous, thermic Typic Ustifluvents

TYPICAL PEDON: Colorado silt loam, in native pastureland.
(Colors are for dry soil unless otherwise stated.)

A--0 to 13 cm (0 to 5 in); light reddish brown (5YR 6/3) silt loam, reddish brown (5YR 4/3) moist; weak fine granular structure; soft, very friable; many fine roots; calcareous; moderately alkaline; abrupt smooth boundary. Thickness is 10 to 41 cm (4 to 16 in].)

C1--13 to 41 cm (5 to 16 in); light reddish brown (5YR 6/3) loam, (stratified with more clayey and more sandy strata) reddish brown (5YR 4/3) moist; massive; slightly hard; friable; few to common earthworm casts; calcareous; moderately alkaline; diffuse smooth boundary. Thickness is 25 to 76 cm (10 to 30 in)

C2--41 to 152 cm (16 to 60 in); light reddish brown (5YR 6/3) stratified loam, reddish brown (5YR 4/3) moist; massive; slightly hard; friable; very thin strata of slightly darker clay loam and fine sandy loam; calcareous; moderately alkaline.

TYPE LOCATION: Runnels County, Texas; from the intersection of U. S. Highways 67 and 83 in Ballinger, 3,400 feet southeast on U. S. Highway 83 and then 500 feet east of Highway 83.
USGS topographic quadrangle: Ballinger, Texas;
Latitude 31 degrees, 43 minutes 50 seconds N;
Longitude 99 degrees, 56 minutes, 24 seconds W.
Datum WGS84.

Soil moisture: Typic-ustic soil moisture regime
Stratification occurs throughout the soil.

Particle-size control section (weighted average):
Texture: silt loam, loam, sandy clay loam, clay loam
Clay content: 18 to 35 percent
Sand fraction: greater than 15 percent coarser than very fine sand
Rock fragments: 0 to 15 percent gravel

A horizon
Hue: 5YR to 10YR
Value: 4 to 6
Chroma: 3 or 4
Epipedon features: horizons with moist values and chroma of less than 3.5 are less than 25 cm (10 in) thick
Reaction (pH): moderately alkaline (7.9 - 8.4)

C horizon(s)
Hue: 2.5YR to 10YR
Value: 4 to 7
Chroma: 3 to 8
Texture: stratified and dominantly silt loam, loam, sandy clay loam, clay loam, but may contain then strata of loamy sand to clay
Structure: stratified platy to massive; in some pedons, part of the C1 horizon shows evidence of weak structural development, but it is not continuous enough to destroy all bedding planes.
Reaction (pH): moderately alkaline (7.9 - 8.4)

COMPETING SERIES: This is the Energy series in the same family. Similar soils include the Bunyan, Clairemont, Mangum, Pulaski, Reinach, Spur, Westola and Yahola series.
Bunyan and Energy soils: have a mean annual precipitation greater than 711 mm (28 in)
Clairemont soils: have less than 15 percent sand fraction that is coarser than very fine sand
Mangum soils: have greater than 35 percent clay in particle-size control section
Pulaski, Westola, and Yahola soils: have less than 18 percent clay in particle-size control section
Reinach and Spur soils: have a mollic epipedon

Parent material: Calcareous loamy alluvium derived from Permian age redbed sediments
Landscape: Dissected plains
Landform: Flood plain
Slope: 0 to 1 percent
Mean annual precipitation: 483 to 711 mm (19 to 28 in)
Thornthwaite annual P-E indices: 24 to 44
Mean annual air temperature: 15.6 to 18.9 degrees C (60 to 66 degrees F)
Frost Free Days: 200 to 230
Elevation: 356.8 to 884.0 meters (1,200 to 2,900 feet)

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Mangum, Clairemont, and Spur series.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate. Runoff is low. Flooding is frequent or occasional, unless protected, and duration is brief or very brief.

USE AND VEGETATION: Mostly rangeland. Predominantly midgrasses with scattered pecan and elm trees along stream channels.

DISTRIBUTION AND EXTENT: Western Texas and Western Oklahoma; Land Resource Region - H; MLRA - 78B and 78C (Central Rolling Red Plains, Western and Eastern Parts). The series is extensive.


SERIES ESTABLISHED: Cottle County, Texas; 1970.

REMARKS: These soils were formerly included in Alluvial land.

Edited 10/2015 (RFG-ROG): Changed to tabular format. Added metric measurements. Updated competing series, geographic setting, and associated soils sections.

Diagnostic horizons and features recognized in this pedon are:
Particle-size control sections: 25 to 100 cm (10 to 40 in). (Parts of the C1 and C2 horizons)
Ochric epipedon: 0 to 13 cm (0 to 5 in). (A horizon)


Taxonomic Version: Keys to Soil Taxonomy, Twelfth Edition, 2014

National Cooperative Soil Survey