LOCATION IRIM                    CO

Established Series
Rev. RHM/GB/KLS
11/2022

IRIM SERIES

The Irim series consists of very deep, poorly drained soils on nearly level to slightly concave or depressed areas of flood plains and low terraces. These soils formed in alluvial sediments derived from a variety of sources. Slopes are 0 to 6 percent. Mean annual precipitation is about 380 mm and the mean annual air temperature is about 4 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Typic Endoaquolls

TYPICAL PEDON: Irim loam, grassland. (Colors are for dry soil unless otherwise noted.)

Oi--0 to 3 cm; undecomposed organic material, mostly grass and roots.

Ag--3 to 31 cm; dark gray (10YR 4/1) loam, black (10YR 2/1) moist; common medium distinct yellowish brown (10YR 5/6) redox concentrations; weak medium subangular blocky structure; very friable, slightly sticky and slightly plastic; 10 percent pebbles; neutral (pH 7.0); gradual wavy boundary. (15 to 58 cm thick)

BCg--31 to 155 cm; grayish brown (10YR 5/2) very gravelly loam, dark grayish brown (10YR 4/2) moist; common medium prominent light olive brown (2.5Y 5/6) and dark gray (2.5Y 4/1) redox concentrations; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; 50 percent pebbles; slightly alkaline (pH 7.4).

TYPE LOCATION: Gunnison County, Colorado; about 1600 meters south of Doyleville, along Tomichi Creek; in SW 1/4, Sec. 34 T. 49 N., R. 3 E.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature--6 degrees C
Mean summer soil temperature--16 degrees C
Irim soils are typically noncalcareous to depths of 150 cm or more; however, depth to uniformly calcareous material can range from 100 to more than 150 cm
Thin organic horizons typically occur on the surface of these soils but are absent in some pedons.

Particle-size control section:
Texture--loam, clay loam, or sandy clay loam
Clay content--18 to 34 percent
Silt content--15 to 50 percent
Sand content--20 to 60 percent
Rock fragment content--35 to 80 percent and are mainly less than 75 mm in diameter but can range from 5 to 250 mm in diameter
Reaction--pH 6.6 to 7.8

Ag horizon
Hue--5YR through 7.5YR
Value--4 or 5 dry, 2 or 3 moist
Chroma--neutral through 2
Distinct or prominent redoximorphic features occur in at least some part of the A horizon.

BCg horizon
Hue--5Y through 7.5YR
Value--5 through 7 dry, 4 through 6 moist
Chroma--neutral through 2
Distinct or prominent redox features, at least part of which has low chroma, occur in this horizon.

COMPETING SERIES: This is the (T) Poronto (MT) series. This series needs further study.

GEOGRAPHIC SETTING:
Landform--flood plains and low terraces
Elevation--2375 to 2600 meters
Slope--0 to 6 percent
Parent material--alluvial sediments derived from a variety of sources
Mean annual precipitation--380 mm with peak periods occurring during the spring and summer
Mean annual air temperature--4 degrees C
Mean summer temperature--17 degrees C
Frost-free period--60 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: None listed

DRAINAGE AND PERMEABILITY: Poorly drained; slow runoff or ponded; moderate permeability

USE AND VEGETATION: These soils are used as native pastureland and for native hay crops. Native vegetation is mainly timothy, redtop, fescues, alsike clover, sedges, and rushes.

DISTRIBUTION AND EXTENT: The Irim series is moderately extensive in the mountain areas of central and western Colorado; MLRAs 48A and 48B

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

SERIES ESTABLISHED: Gunnison County, Colorado, 1974

REMARKS: Diagnostic horizons and features recognized in this pedon include:
Mollic epipedon--3 to 31 cm (Ag horizon)
Aquic conditions--3 to 155 cm (Ag and BCg horizons)

Converted to metric, updated formatting, and O horizons were updated to start at zero. Competing series section was not updated. 11/2022

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National Cooperative Soil Survey
U.S.A.