LOCATION DUBAY MT
Established Series
Rev. PHO-DJP-BDM
08/2026
DUBAY SERIES
The Dubay series consists of very deep, well drained soils that formed in alluvium, glaciofluvial and lacustrine deposits. These soils are on stream terraces, lake terraces and alluvial fans. Slopes are 0 to 30 percent. Mean annual precipitation is about 486 centimeters, and mean annual temperature is about 6 degrees C.
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, frigid Lamellic Haploxerepts
TYPICAL PEDON: Dubay silt loam, in coniferous forest (colors are for dry soil unless otherwise noted).
Oi--0 to 3 centimeters; undecomposed and slightly decomposed forest litter; very strongly acid (pH 5.0).
A--3 to 15 centimeters; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; slightly hard, very friable, nonsticky and nonplastic; many fine and medium roots; many fine and medium pores; neutral (pH 6.8); clear irregular boundary. (8 to 20 centimeters thick)
E1--15 to 33 centimeters; pale brown (10YR 6/3) silt loam, brown (10YR 4/3) moist; weak coarse subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; many fine roots; many fine and medium pores; neutral (pH 7.0); gradual irregular boundary.
E2--33 to 79 centimeters; very pale brown (10YR 7/3) silt loam, brown (10YR5/3) moist; weak coarse subangular blocky structure; hard, very friable, nonsticky and nonplastic; many fine roots; many fine pores; neutral (pH 7.0); gradual irregular boundary. (Combined thickness of the E horizons is 13 to 89 centimeters)
E and Bw--79 to 152 centimeters; E part (70 percent) very pale brown (10YR 7/3) silt loam, pale brown (10YR 6/3) moist; Bw part (30 percent) yellowish brown (10YR 5/4) very fine sandy loam, dark yellowish brown (10YR 4/4) moist, lamellae 0.6 to 1.3 centimeters thick and total less than 8 centimeters thick; massive; slightly hard, very friable, nonsticky and nonplastic; common fine roots; common fine pores; neutral (pH 7.0).
TYPE LOCATION: Lake County, Montana; 305 meters south and 61 meters west of the NE corner of sec. 18, T. 22 N., R. 19 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 5 to 8 degrees C.
Moisture control section - between 10 and 30 centimeters; moist during December through March and dry for more than 45 consecutive days during July, August, and early September.
Control section - 5 to 15 percent clay and less than 15 percent fine sand or coarser, and 0 to 10 percent pebbles.
The dark colored surface of this soil does not meet the thickness requirements for a mollic epipedon. Some pedons have free lime below a depth of 30 centimeters.
A horizon
Hue: 7.5YR or 10YR
Value: 4 or 6 dry; 2 or 4 moist
Chroma: 1 or 3
Texture: silt loam or very fine sandy loam
Clay content: 5 to 18 percent
Rock fragments: 0 to 10 percent pebbles
Reaction: pH 5.6 to 7.3
E1 and E2 horizons
Hue: 7.5YR or 10YR
Value: 5, 6, or 7 dry; 4 or 5 moist
Chroma: 2 or 3
Texture: silt loam or very fine sandy loam
Clay content: 5 to 15 percent
Rock fragments: 0 to 10 percent pebbles
Reaction: pH 5.6 to 7.3
E and Bw horizon
Hue: 7.5YR or 10YR
Value: E part 5, 6 or 7, B part 4, 5 or 6 dry; E part 4, 5, or 6, B part 4 or 5 moist
Chroma: E part 2 or 3; B part 2, 3, or 4
Texture: silt loam or very fine sandy loam
Clay content: 5 to 15 percent
Rock fragments: 0 to 10 percent pebbles
Reaction: pH 6.0 to 8.0
BC and C (when present)
Hue: 7.5YR or 10YR
Value: 5, 6, or 7 dry; 4, 5, or 6 moist
Chroma: 3 or 4
Texture: silt loam or very fine sandy loam
Clay content: 5 to 15 percent
Reaction: pH 7.4 to 8.0
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - alluvial fans, stream terraces and lake terraces.
Elevation - 701 to 1,372 meters.
Slope- 0 to 30 percent.
Parent material - alluvium, lacustrine and glaciofluvial deposits.
Climate - long, cold winters; moist falls and springs; warm, dry summers.
Mean annual precipitation - 410 to 563 centimeters.
Mean annual temperature - 4 to 7 degrees C.
Frost-free period - 90 to 125 days.
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderate permeability through the E2 horizon and moderately slow permeability in the E and Bw horizon.
USE AND VEGETATION: Dubay soils are used mainly for irrigated and non-irrigated crops, pasture, and for timber production. Potential native vegetation is mainly ponderosa pine and Douglas-fir with an understory of common snowberry, pinegrass, and Oregon grape.
DISTRIBUTION AND EXTENT: Dubay soils are of small extent in northwestern Montana valleys. MLRA 44A.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Lake County, Montana, 1991; proposed in Lake County, Montana, 1982.
REMARKS: Soil interpretation record: MT0746. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from the mineral soil surface to 15 centimeters (A horizon); an albic horizon from 15 to 79 centimeters (E1 and E2 horizons); and a particle-size control section from 25 to 100 centimeters below the mineral soil surface (E1, E2, E and Bw horizons). Dubay soils have a frigid temperature regime and a xeric moisture regime.
The 4/2026 description reflects a broadening of the Range In Characteristics and update from English to metric units of measurement.
National Cooperative Soil Survey
U.S.A.