LOCATION COLBY                   KS+CO MT NE SD WY

Established Series
Rev. SAG


The Colby series consists of very deep, well drained and somewhat excessively drained, moderately permeable soils that formed in loess. Colby soils are on plains and hillslopes on tableland in the Central High Tableland (MLRA 72). Slopes range from 0 to 60 percent. Mean annual precipitation is about 450 millimeters (18 inches) and the mean annual temperature is about 11 degrees C (52 degrees F).

TAXONOMIC CLASS: Fine-silty, mixed, superactive, calcareous, mesic Aridic Ustorthents

TYPICAL PEDON: Colby silt loam, on an east-facing, convex, 1 percent slope in grassland, at an elevation of 1,031 meters (3,382 feet). (Colors are for dry soil unless otherwise stated.)

A--0 to 10 cm (0 to 4 inches); grayish brown (10YR 5/2) silt loam, dark grayish brown (10YR 4/2) moist; weak fine platy structure to a depth of 5 cm (2 inches), weak fine granular structure below 5 cm (2 inches); slightly hard, friable; strong effervescence; moderately alkaline; gradual smooth boundary. (8 to 15 cm (3 to 6 inches) thick)

AC--10 to 20 cm (4 to 8 inches); light brownish gray (10YR 6/2) silt loam, grayish brown (10YR 5/2) moist; weak fine granular structure; slightly hard, friable; strong effervescence; moderately alkaline; gradual smooth boundary. (0 to 23 cm (0 to 9 inches) thick)

C1--20 to 51 cm (8 to 20 inches); pale brown (10YR 6/3) silt loam, brown (10YR 5/3) moist; massive; slightly hard, friable; few fine roots and root channels; porous; few soft lime accumulations; violent effervescence; moderately alkaline; gradual wavy boundary. (25 to 76 cm (10 to 30 inches) thick)

C2--51 to 200 cm (20 to 79 inches); very pale brown (10YR 7/3) silt loam, light yellowish brown (10YR 6/4) moist; massive; slightly hard, friable; porous; violent effervescence; moderately alkaline.

TYPE LOCATION: Hamilton County, Kansas; about 4 kilometers (2.5 miles) north of Syracuse; 0.5 kilometers (0.3 miles) north of the southwest corner of section 30, T. 23 S., R. 40 W; Plum Creek South USGS quadrangle.

The thickness of the solum ranges from 8 to 30 centimeters (3 to 12 inches).
Particle-size control section: 19 to 34 percent clay by weighted average
Typically these soils have free carbonates at the surface, but some pedons are carbonate free in the upper 15 centimeters (6 inches). Calcium carbonate equivalent is less than 5 percent in the upper part of the profile.

The A horizon or Ap (where present):
Hue: 10YR
Value: 5 to 7 and 3 to 5 moist
Chroma: 2 or 3
Horizons having value of 5 or less dry or 3 or less moist and a chroma of 3 or less are less than 10 centimeters (4 inches) thick.
Texture: silt loam, loam, silty clay loam, sandy loam or very fine sandy loam
Reaction: mildly alkaline or moderately alkaline

The AC and C horizons:
Hue: 2.5Y to 7.5YR
Value: 5 to 8 and 4 to 6 moist
Chroma: 2 to 4
Texture: silt loam or loam
Reaction: slightly alkaline to strongly alkaline
Visible accumulation of carbonates in the C1 horizon occur as films on ped faces or soft masses. It is not a calcic horizon, and the horizon is not regarded as definitive for the series.

COMPETING SERIES: The Bainville series.
Bainville soils have a paralithic contact within 102 centimeters (40 inches).

Parent material: loess
Landform: nearly level to steep hillslopes and plains
Landscape: tableland
Slopes: commonly 3 to 15 percent but range from 0 to 60 percent
Mean annual air temperature: 7 to 13 degrees C (45 to 55 degrees F)
Mean annual precipitation: 33 to 51 centimeters (13 to 20 inches)

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Keith, Richfield, and Ulysses soils.
Keith and Richfield soils have mollic epipedons and are commonly on the nearly level areas above the Colby.
Ulysses soils are on gently sloping to strongly sloping areas adjacent to the Colby soils.

Drainage: Well drained to somewhat excessively drained
Runoff: negligible to high
Saturated hydraulic conductivity: moderately high

USE AND VEGETATION: Mostly in native range. The less sloping areas are cultivated to irrigated wheat and sorghum. Native vegetation is mostly short grasses.

DISTRIBUTION AND EXTENT: Western Kansas, eastern Colorado, western Nebraska, southwestern South Dakota, and eastern Montana in MLRA 64, 67, and 72. The series is extensive.


SERIES ESTABLISHED: Reconnaissance Soil Survey of Western Kansas, 1910.

REMARKS: Colby soils were formerly classified as Ustic Torriorthents.
Diagnostic horizon recognized is the ochric epipedon (A horizon) 0 to 10 cm (0 to 4 inches).
Modified format to meet MO5 standards. TDC 04/2012
Added Mean Annual Precipitation and Mean Annual Air Temperature to the introduction. TDC 04/2012
Removed Manvel, Minnequa, and Rocky Ford series from Competing Series, based on current classification. TDC 04/2012
Added Particle size control section to the Range in Characteristics. TDC 04/2012
Removed the calcareous modifier from the parent material description. TDC 04/2012

National Cooperative Soil Survey