LOCATION COLBY KS+CO MT NE SD WYEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, calcareous, mesic Aridic Ustorthents
TYPICAL PEDON: Colby silt loam, grassland. (Colors are for dry soil unless otherwise stated.)
A--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 2 inches, weak fine granular structure below 2 inches; slightly hard, friable; strong effervescence; moderately alkaline; gradual smooth boundary. (3 to 6 inches thick)
AC--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 9 inches thick)
C1--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. (10 to 30 inches thick)
C2--20 to 80 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 2.5 miles north of Syracuse; 0.3 mile north of the southwest corner of sec. 30, T. 23 S., R. 40 W.
RANGE IN CHARACTERISTICS: The thickness of the solum ranges from 3 to 12 inches. Typically these soils have free carbonates at the surface, but some pedons lack carbonates in the upper 6 inches. Calcium carbonate equivalent is less than 5 percent in the upper part of the profile.
The A horizon has color value of 5 to 7 and 3 to 5 moist, and chroma of 2 or 3. Horizons having value of less than 5.5 dry or 3.5 moist are less than 4 inches thick. The A horizon is silt loam, loam, silty clay loam, sandy loam or very fine sandy loam, and is mildly alkaline or moderately alkaline.
The AC and C horizons have hue of 2.5Y to 7.5YR, value of 5 to 8 and 4 to 6 moist, and chroma of 2 to 4. they are silt loam or loam and are slightly to strongly alkaline. Visible accumulation of carbonates in the C1 horizon occurs 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: These are the Bainville, Manvel, Minnequa, and Rocky Ford series. Bainville and Minnequa soils have paralithic contact within 40 inches. Manvel soils have more than 5 percent calcium carbonate equivalent in the surface. Rocky Ford soils have a thick man-made Ap horizon.
GEOGRAPHIC SETTING: Colby soils are on nearly level to steep hills and plains. Slope gradients are commonly 3 to 15 percent but range from 0 to 60 percent. The soils formed in calcareous silty loess. Mean annual precipitation ranges from 13 to 20 inches, and mean annual temperature ranges from 45 to 55 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Keith, Richfield, and Ulysses soils, all of which have mollic epipedons. Keith and Richfield soils commonly are on the nearly level areas above the Colby. Ulysses soils are on gently sloping to strongly sloping areas above Colby soils.
DRAINAGE AND PERMEABILITY: Well drained to somewhat excessively drained. Runoff is low to very high. Permeability is moderate.
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.
MLRA OFFICE RESPONSIBLE: Salina, Kansas
SERIES ESTABLISHED: Reconnaissance Soil Survey of Western Kansas, 1910.
REMARKS: Colby soils were formerly classfied as Ustic Torriorthents. Diagnostic horizon recognized is ochric epipedon (A horizon)