LOCATION IRAK                    CO

Established Series
Rev. ABP-JWH-KLS
05/2023

IRAK SERIES

The Irak series consists of very deep, moderately well or somewhat poorly drained soils that formed in alluvium derived from reworked eolian material. Irak soils are in drainageways and draws on low terraces. Slopes range from 0 to 3 percent. Mean annual precipitation is about 355 mm and the mean annual air temperature is about 9 degrees C.

TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Cumulic Haplustolls

TYPICAL PEDON: Irak loam - pasture. (Colors are for dry soil unless otherwise noted.)

A1--0 to 20 cm; reddish brown (5YR 5/3) loam, dark reddish brown (5YR 3/3) moist; weak medium subangular blocky structure parting to weak fine granular; slightly hard, friable, slightly sticky and slightly plastic; slightly effervescent; slightly alkaline (pH 7.5); abrupt smooth boundary. (18 to 30 cm thick)

C1--20 to 33 cm; reddish brown (5YR 4/3) loam, dark reddish brown (5YR 3/3) moist; strong thick platy structure; hard, friable, slightly sticky and slightly plastic; slightly effervescent; slightly alkaline (pH 7.6); abrupt smooth boundary.

C2--33 to 109 cm; reddish brown (5YR 4/3) loam, dark reddish brown (5YR 3/3) moist; weak coarse prismatic structure parting to weak coarse subangular blocky; hard, friable, slightly sticky and slightly plastic; slightly effervescent; slightly alkaline (pH 7.5); clear smooth boundary. (Combined thickness of C1 and C2 horizons - 40 to 125 cm)

C3--109 to 152 cm; reddish brown (5YR 4/3) loam, dark reddish brown (5YR 3/3) moist; weak medium subangular blocky structure; very hard, friable, slightly sticky and slightly plastic; slightly effervescent; slightly alkaline (pH 7.6).

TYPE LOCATION: Montezuma County, Colorado; about 3 km west of the community of Yellow Jacket, located about 52 meters east and 229 meters south of the northwest corner of sec. 29, T. 38 N., R. 17 W.; Dolores East USGS quad; lat. 37 degrees, 36 minutes, 56 seconds N. and long. 108 degrees, 45 minutes, 16 seconds W., NAD27

RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 8 to 11 degrees C
Thickness of the mollic epipedon - more than 50 cm
Depth to water table - 30 to 100 centimeters below ground surface from April to September

Particle-size control section:
Clay content - 18 to 35 percent
Sand content - less than 15 percent fine sand and coarser and up to 35 percent very fine sand
Rock fragment content - 0 to 15 percent

A horizon
Hue: 5YR or 7.5YR
Value: 3 to 5 dry, 2 or 3 moist
Chroma: 2 or 3 dry or moist
Calcium carbonate equivalent: 0 to 5 percent
Reaction: pH 6.6 to 8.4

C horizon
Hue: 5YR or 7.5YR
Value: 3 to 5 dry, 2 to 4 moist
Chroma: 2 to 4 dry or moist
Texture: loam or clay loam
Calcium carbonate equivalent: 1 to 5 percent
Reaction: pH 6.6 to 8.4

COMPETING SERIES:
Ackmen (UT) - do not have a water table April through September
Alcester (SD) - have hues of 10YR or yellower throughout
Coleridge (NE) - have hues of 10YR or yellower throughout
Gabalon (NM) - do not have a water table April through September
Hord (NE) - have hues of 10YR or yellower throughout
Muir (KS) - do not have a water table April through September
Roxbury (KS) - do not have a water table April through September
Shell (NE) - have hues of 10YR or yellower throughout
Tobin (KS) - have hues of 10YR or yellower throughout
Trementina (CO) - do not have a water table April through September
Vega (UT) - do not have a water table April through September
Waka (OK) - do not have a water table April through September

GEOGRAPHIC SETTING:
Landform - drainageways, low terraces and draws
Elevation - 1,600 to 2,250 meters
Slopes - 0 to 3 percent
Parent material - alluvium derived from reworked eolian material
Mean annual air temperature - 7 to 10 degrees C
Mean annual precipitation - 330 to 410 mm
Precipitation pattern - Monthly precipitation is evenly distributed throughout the year with July and August being slightly wetter and June being slightly dryer.
Frost-free period: 100 to 140 days

GEOGRAPHICALLY ASSOCIATED SOILS: None listed.

DRAINAGE AND PERMEABILITY: moderately well or somewhat poorly drained, negligible to medium runoff, moderate or moderately slow permeability

USE AND VEGETATION: Irak soils are used for livestock grazing, pasture, crops, and wildlife habitat. Native vegetation is alkali sacaton, western wheatgrass, inland saltgrass, and sedges.

DISTRIBUTION AND EXTENT: Irak soils are of small extent in southwest Colorado and along the eastern front of the Rocky Mountains in northern Colorado; MLRA 36 and 49.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Cortez Area, Colorado, Parts of Dolores and Montezuma Counties 1997.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 152 cm (A, C1, C2, and C3 horizons)
Water table - 30 to 100 centimeters below ground surface from April to September
Redoximorphic features - high chroma redox concentrations occur in the lower part of some pedons below 100 cm
Particle size control section - 25 to 100 cm (parts of the C1, C2 horizons)

Irak soils have a mesic soil temperature regime and an ustic soil moisture regime bordering on aridic.

Converted to metric, formatting updated to current standards, and competing series section updated. 12/2020

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National Cooperative Soil Survey
U.S.A.