LOCATION OWENFORT MT
Established Series
Rev. JMS/EMR/RJS
07/2013
OWENFORT SERIES
The Owenfort series consists of very deep, well drained soils formed in alluvium or outwash. These soils are on alluvial fans, stream terraces, inset fans and outwash fans. Slopes are 0 to 8 percent. Mean annual precipitation is about 330 mm, and mean annual air temperature is about 6.0 degrees C.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Aridic Haplustolls
TYPICAL PEDON: Owenfort cobbly loam, rangeland on a 2 percent slope at 1,039 meters elevation (colors are for dry soil unless otherwise noted).
A1--0 to 13 cm; grayish brown (10YR 5/2) cobbly loam, very dark grayish brown (10YR 3/2) moist; moderate medium granular structure; soft, very friable, nonsticky and nonplastic; many fine roots; many fine irregular and tubular pores; 15 percent gravel and 15 percent cobbles; neutral (pH 6.8); gradual smooth boundary.
A2--13 to 25 cm; grayish brown (10YR 5/2) very cobbly loam, very dark grayish brown (10YR 3/2) moist; moderate medium granular structure; soft, very friable, nonsticky and nonplastic; many fine roots; many fine irregular and tubular pores; 20 percent gravel and 15 percent cobbles; neutral (pH 6.8); gradual smooth boundary. (combined thickness of the A horizons - 25 to 40 cm)
BC--25 to 61 cm; pale brown (10YR 6/3) very gravelly sandy loam, brown (10YR 4/3) moist; weak medium granular structure; soft, very friable, nonsticky and nonplastic; many fine roots; many fine irregular pores; 45 percent gravel and 10 percent cobbles; neutral (pH 7.0); gradual wavy boundary. (30 to 85 cm thick)
C1--61 to 107 cm; pale brown (10YR 6/3) very gravelly sandy loam, brown (10YR 4/3) moist; massive; soft, very friable, nonsticky and nonplastic; many very fine roots; many fine irregular pores; 45 percent gravel and 10 percent cobbles; neutral (pH 7.0); gradual wavy boundary. (13 to 51 cm thick)
C2--107 to 152 cm; pale brown (10YR 6/3) extremely gravelly sandy loam, brown (10YR 4/3) moist; single grain; loose, nonsticky and nonplastic; few very fine roots; many fine irregular pores; 55 percent gravel and 10 percent cobbles; neutral (pH 6.8).
TYPE LOCATION: Bing topographic quadrangle, Ravalli County, Montana; 230 meters west and 1,193 meters north of the SE corner of sec. 35, T.9N, R.20W; UTM zone 11, 724861E, 5152926N, NAD 83.
RANGE IN CHARACTERISTICS:
Soil temperature - 5.0 to 8.0 degrees C.
Moisture control section - between 20 and 60 cm
Mollic epipedon thickness - 25 to 40 cm
Note: Some pedons may have a thin Bw horizon below the A horizon.
A horizons
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3; dry or moist
Texture: loam or sandy loam
Clay content: 14 to 22 percent
Rock fragments: 15 to 50 percent--10 to 25 percent gravel, 0 to 25 percent cobbles, 0 to 5 percent stones
Reaction: pH 6.4 to 7.8
BC horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 3 or 4 moist
Chroma: 3 or 4; dry or moist
Texture: loam or sandy loam
Clay content: 10 to 20 percent
Rock fragments: 35 to 60 percent--15 to 45 percent gravel, 10 to 25 percent cobbles, 0 to 5 percent stones
Reaction: pH 6.4 to 7.8
C1 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 to 4; dry or moist
Clay content: 5 to 16 percent
Rock fragments: 50 to 85 percent--20 to 50 percent gravel, 10 to 25 percent cobbles, 0 to 5 percent stones
Reaction: pH 6.6 to 7.8
C2 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 6 or 7 dry; 4 or 5 moist
Chroma: 2 to 4; dry or moist
Texture: sandy loam, loamy sand or sand
Clay content: 0 to 12 percent
Rock fragments: 50 to 85 percent--30 to 55 percent gravel, 10 to 25 percent cobbles, 0 to 10 percent stones
Reaction: pH 6.6 to 7.8
COMPETING SERIES:
Bulltop (ND) - have secondary calcium carbonate accumulation
Dolus (MT) - are moderately deep to a paralithic contact
Frenchcreek (MT) - have a cambic horizon
Sixbeacon (MT) - have secondary calcium carbonate accumulation
GEOGRAPHIC SETTING:
Landform - alluvial fans, stream terraces, inset fans and outwash fans
Elevation - 915 to 1,800 meters
Slope - 0 to 8 percent
Parent material - alluvium or outwash
Climate - long, cold winters; moist springs; warm summers
Mean annual air temperature - 5.0 to 8.0 degrees C.
Mean annual precipitation - 300 to 360 mm
Frost-free period - 90 to 115 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; moderate to moderately rapid permeability.
USE AND VEGETATION: Owenfort soils are used mainly for rangeland, irrigated pasture and hayland. Potential native vegetation is bluebunch wheatgrass, needleandthread, prairie junegrass, and blue grama.
DISTRIBUTION AND EXTENT: Owenfort soils are of small extent in intermountain valleys of western Montana. MLRA - 44A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Bitterroot Valley Area, Montana, 2013; proposed in Ravalli County, Montana, 2006.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 25 cm (A1, A2 horizons)
Particle-size control section - 25 to 100 cm (BC, part of the C1 horizons)
Owenfort soils have a frigid temperature regime and an ustic moisture regime and an aridic moisture subclass.
National Cooperative Soil Survey
U.S.A.