LOCATION KOKORUDA                MT

Established Series
Rev. PEM-JAL-KLS
05/2023

KOKORUDA SERIES

The Kokoruda series consists of very deep, well drained soils that formed in alluvium from mixed rock sources. These soils are on alluvial fans, swales, drainageways and sideslopes of hills. Slopes are 8 to 35 percent. Mean annual precipitation is about 480 mm, and mean annual air temperature is about 4 degrees C.

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Typic Argiustolls

TYPICAL PEDON: Kokoruda loam, in forest (colors are for dry soil unless otherwise noted).

Oi--0 to 3 cm; leaves, twigs, roots, and partially decomposed leaves and twigs.

A1--3 to 16 cm; dark gray (10YR 4/1) loam, very dark gray (10YR 3/1) moist; weak medium and fine subangular blocky structure; soft, very friable, moderately sticky and slightly plastic; many very fine and few fine, medium and coarse roots; many very fine and few fine pores; 10 percent gravel; slightly acid (pH 6.2); clear wavy boundary.

A2--16 to 31 cm; dark gray (10YR 4/1) cobbly loam, very dark gray (10YR 3/1) moist; weak medium and fine subangular blocky structure; soft, very friable, moderately sticky and slightly plastic; many very fine and few fine, medium, and coarse pores; 15 percent cobbles, 15 percent gravel; slightly acid (pH 6.1); clear smooth boundary. (Combined thickness of A horizons - 18 to 38 cm)

Bt1--31 to 41 cm; pale brown (10YR 6/3) cobbly clay loam, brown (10YR 5/3) moist; weak medium prismatic structure parting to moderate medium and fine subangular blocky; slightly hard, friable, moderately sticky and slightly plastic; many very fine and few fine, medium, and coarse roots; many very fine and few fine tubular and interstitial pores; many faint clay films on faces of peds and bridging sand grains; 15 percent cobbles, 10 percent gravel; neutral (pH 6.6); clear wavy boundary.

Bt2--41 to 87 cm; light yellowish brown (10YR 6/4) cobbly clay loam, brown (10YR 5/3) moist; moderate medium prismatic structure parting to moderate medium and fine subangular blocky; slightly hard, friable, moderately sticky and slightly plastic; many very fine and few fine and medium roots; many very fine and few fine tubular and interstitial pores; many faint clay films on faces of peds and bridging sand grains; 15 percent cobbles, 15 percent gravel; slightly acid (pH 6.1); clear wavy boundary. (Combined thickness of Bt horizons - 38 to 89 cm)

BC--87 to 156 cm; pale brown (10YR 6/3) very cobbly clay loam, light olive brown (2.5Y 5/4) moist; moderate medium and fine subangular blocky structure; slightly hard, friable, moderately sticky and slightly plastic; few very fine and fine roots; common very fine and few fine tubular and interstitial pores; 20 percent cobbles, 25 percent gravel; slightly acid (pH 6.1).

TYPE LOCATION: Jefferson County, Montana; about 790 meters south and 45 meters east of the NW corner of sec. 30, T. 9 N., R. 2 W.

RANGE IN CHARACTERISTICS:
Soil temperature--3 to 7 degrees C
Moisture control section--10 to 30 cm
Thickness of mollic epipedon--18 to 38 cm

A horizons
Hue--10YR or 2.5Y
Value--3 or 4 dry; 2 or 3 moist
Clay content--10 to 27 percent
Rock fragment content--10 to 35 percent; 0 to 15 percent cobbles, 10 to 20 percent gravel
Reaction--pH 6.1 to 7.3

Bt horizons
Hue--10YR or 2.5Y
Value--5 or 6 dry; 3, 4, or 5 moist
Chroma--2, 3, or 4
Texture--sandy clay loam, loam, or clay loam
Clay content--18 to 35 percent
Rock fragment content--10 to 35 percent; 0 to 15 percent cobbles, 10 to 20 percent gravel
Reaction--pH 6.1 to 7.3

BC horizon
Hue--10YR or 2.5Y
Value--5 or 6 dry; 4 or 5 moist
Chroma--3, 4, or 6
Texture--sandy loam, sandy clay loam, loam, or clay loam
Clay content--15 to 30 percent
Rock fragment content--20 to 50 percent; 0 to 20 percent cobbles, 20 to 30 percent gravel
Reaction--pH 5.6 to 7.3

COMPETING SERIES:
Bottineau (ND) - has horizon of secondary carbonate accumulation, formed in till.
Doughty (MT) - has calcic horizon; has discontinuity with more than 50 percent coarse fragments.
Farside (MT) - does not have an O horizon.
Forman (ND) - has horizons of secondary carbonate accumulation; formed in till.
Sipple (MT) - has calcic horizon; has discontinuity with more than 50 percent coarse fragments. Watne (MT) - has calcic horizon.

GEOGRAPHIC SETTING:
Landform--alluvial fans, drainageways, swales and sideslopes of hills
Elevation--1350 to 1825 meters
Slope--8 to 35 percent
Parent material--alluvium derived from mixed rock sources
Climate--long, cold winters; moist springs; warm summers
Mean annual precipitation--380 to 610 mm
Mean annual air temperature--2 to 6 degrees C
Frost-free period--70 to 105 days

GEOGRAPHICALLY ASSOCIATED SOILS: None listed.

DRAINAGE AND PERMEABILITY: Well drained, moderately slow permeability.

USE AND VEGETATION: Kokoruda soils are primarily used for woodland and wildlife habitat. The potential native vegetation is mainly quaking aspen, common snowberry, white spiraea, western yarrow, woodland strawberry, northern bedstraw, heartleaf arnica, woods rose, Kentucky bluegrass, pinegrass, mahonia, timothy, clover, moderately sticky geranium, danthonia, and mountain brome.

DISTRIBUTION AND EXTENT: Kokoruda soils are of small extent in southwestern Montana; MLRA 43B.

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

SERIES ESTABLISHED: Jefferson County, Montana, 1998.

REMARKS: Soil interpretation record: MT1503.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon--3 to 31 cm (A1 and A2 horizons)
Argillic horizon--31 to 87 cm (Bt1 and Bt2 horizons)
Particle-size control section--31 to 81 cm (Bt1 and Bt2 horizons)

Kokoruda soils have a frigid temperature regime and an ustic soil moisture regime.

Converted to metric and O horizons were updated to start at zero. Competing series section was not updated. 05/2023

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National Cooperative Soil Survey
U.S.A.