LOCATION HAWKSELL                CO

Established Series
Rev. TWH
01/2012

HAWKSELL SERIES

The Hawksell series consists of very deep, well drained soils that formed in slope alluvium. Hawksell soils are on footslopes of escarpments and on pediments. Slopes range from 5 to 9 percent. Mean annual precipitation is about 300 mm (12 inches) and the mean annual temperature is about 6.7 degrees C (46 degrees F).

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, frigid Aridic Haplustepts

TYPICAL PEDON: Hawksell sandy loam, on a southeast facing slope in an irrigated grain field at an elevation of 2220 meters (7280 feet). (Colors are for dry soil unless otherwise noted.)

A--0 to 18 cm (0 to 7 inches); grayish brown (10YR 5/2) crushed, sandy loam, dark grayish brown (10YR 4/2) crushed, moist; weak fine granular structure; slightly hard, friable, nonsticky; common fine roots throughout and common medium roots throughout; 5 percent gravel; noneffervescent (2 percent calcium carbonate equivalent); moderately alkaline (pH 7.9); clear smooth boundary. (10 to 24 cm thick)

Bw--18 to 51 cm (7 to 20 inches); 80 percent grayish brown (10YR 5/2) and 20 percent brown (10YR 5/3) sandy loam, 80 percent dark grayish brown (10YR 4/2) and 20 percent brown (10YR 4/3) moist; massive; slightly hard, friable, slightly sticky; few fine roots throughout; 10 percent gravel; slightly effervescent (1 percent calcium carbonate equivalent); moderately alkaline (pH 7.9); clear smooth boundary. (20 to 46 cm thick)

Bk--51 to 66 cm (20 to 26 inches); 50 percent gray (10YR 6/1) and 50 percent grayish brown (10YR 5/2) sandy loam, 50 percent gray (10YR 5/1) and 50 percent dark grayish brown (10YR 4/2) moist; massive; slightly hard, friable, nonsticky; few fine roots throughout; 5 percent gravel; strongly effervescent (3 percent calcium carbonate equivalent); moderately alkaline (pH 8.2); clear wavy boundary. (10 to 30 cm thick)

C--66 to 152 cm (26 to 60 inches); 80 percent grayish brown (10YR 5/2) and 20 percent brown (10YR 5/3) loamy sand, 80 percent dark grayish brown (10YR 4/2) and 20 percent brown (10YR 4/3) moist; massive; loose, nonsticky; 5 percent gravel; slightly effervescent (1 percent calcium carbonate equivalent); moderately alkaline (pH 8.1).

TYPE LOCATION: Chaffee County, Colorado; about 3 kilometers (2 miles) west of Salida; about one-fourth mile east of the southwest corner of sec. 36, T. 50 N., R. 8 E.; Salida West USGS quad; lat. 38 degrees 32 minutes 08 seconds N. and long. 106 degrees 02 minutes 07 seconds W., NAD WGS84.

RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section usually dry in late spring and early summer, moist in some part in late July and August, and intermittently dry in fall; ustic moisture regime bordering on aridic.
Mean annual soil temperature: 6 to 7 degrees C (44 to 46 degrees F)
Mean summer soil temperature: 17 to 19 degrees C (62 to 66 degrees F).
Depth to free carbonates: below 18 cm (below 7 inches)
Depth to secondary calcium carbonate: 45 to 64 cm (18 to 25 inches)

Particle-size control section (weighted averages):
Noncarbonate clay content: 10 to 14 percent
Fine sand and coarser sand content: 50 to 75 percent
Rock fragment content: 5 to 10 percent

A horizon (Ap horizon in some pedons):
Value: 5 dry, 4 moist
Chroma: 2 or 3, dry or moist
Clay content: 8 to 17 percent
Rock fragment content: 1 to 10 percent

Bw horizon:
Value: 5 dry, 4 moist
Chroma: 2 or 3, dry or moist
Clay content: 8 to 17 percent
Rock fragment content: 1 to 10 percent
Calcium carbonate equivalent: 0 to 3 percent

Bk horizon:
Value: 5 or 6 dry, 4 moist
Chroma: 1 or 2, dry or moist
Clay content: 8 to 17 percent
Rock fragment content: 3 to 10 percent
Calcium carbonate equivalent: 1 to 5 percent
Reaction: moderately alkaline or strongly alkaline
This horizon may contain thin lenses (less than 10 cm thick) of gravel.

C horizon (Bk or BCk horizon in some pedons):
Value: 5 dry, 4 moist
Chroma: 2 or 3, dry or moist
Texture: loamy sand, sandy loam
Clay content: 4 to 16 percent
Rock fragment content: 3 to 10 percent
Calcium carbonate equivalent: 1 to 5 percent
Reaction: moderately alkaline or strongly alkaline
This horizon may contain thin lenses (less than 10 cm thick) of gravel.

COMPETING SERIES: These are the Spang and Toby series. Spang soils have hue redder than 10YR. Toby soils do not have horizons of secondary carbonate accumulations, and are presumed to be more moist in the moisture control section in early summer.

GEOGRAPHIC SETTING:
Parent material: calcareous, moderately coarse textured slope alluvium
Landform: pediments, footslopes of escarpments
Slopes: 5 to 9 percent
Elevation: 2130 to 2600 meters (7,000 to 8,500 feet)
Mean annual temperature: 6.0 to 8.0 degrees C (43 to 46 degrees F)
Mean annual precipitation: 280 to 380 mm (11 to 15 inches)
Precipitation pattern: evenly distributed except for dry in late spring and early summer, and a peak in late summer.
Frost-free period: 60 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Blanyon and St. Elmo series. The Blanyon soils are clayey and are on less sloping areas of pediments or stream terraces. The St. Elmo soils are sandy-skeletal, have stronger carbonate accumulations and are on higher stream terraces.

DRAINAGE AND PERMEABILITY: Well drained, slow runoff, moderate permeability.

USE AND VEGETATION: Used mainly for irrigated crops and hay. Historical native potential vegetation is mainly Indian ricegrass, needleandthread, sand dropseed, blue grama, bottlebrush squirreltail, fourwing saltbush, and winterfat.

DISTRIBUTION AND EXTENT: Central Colorado; MLRA 49; small extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Chaffee County, Colorado; Chaffee-Lake Area soil survey area, 1968. The name is was originally "Hawk" then coined as Hawksell.

REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Series control section: The zone from 0 to 150 cm.
Particle-size control section: The zone from 25 to 100 cm (part of Bk, part of C horizons).
Ochric epipedon: from 0 to 18 cm (A horizon).
Cambic horizon: from 18 to 66 cm (Bw and Bk horizons).
Secondary carbonates: from 51 to 66 cm (Bk horizons).

Taxonomic Version: Classified according to Keys to Soil Taxonomy, Eleventh Edition, 2010.

Although established in 1968, an official series description for this series could not be found. In January 2012 an OSD was drafted based on the series description in the published soil survey and supplemented with information from the lab-sampled pedon. The series classification when established was Coarse-loamy, mixed (calcareous), frigid Ustic Torriorthents.

Landforms in the soil survey report were identified as "colluvial-alluvial slopes and fans". Examination of contour maps indicates landforms are more likely pediments below higher terraces and below bedrock-controlled uplands.

ADDITIONAL DATA: A very similar pedon at the same location as the series type location was sampled in 1957 for the Soil Survey Laboratory in Ft. Collins, CO; lab sample number S-57-Colo-8-4.

---

National Cooperative Soil Survey
U.S.A.