LOCATION RAVALLI MT
Established Series
Rev. AA/RJE/RJS
02/2013
RAVALLI SERIES
The Ravalli series consists of very deep, well drained soils that formed in alluvium, outwash or slope alluvium. These soils are on fan remnants, eroded fan remnants and outwash fans. Slopes are 0 to 45 percent. Mean annual precipitation is about 350 mm, and mean annual air temperature is about 6.0 degrees C.
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Typic Natrustalfs
TYPICAL PEDON: Ravalli silt loam, native grass. (colors are for dry soil unless otherwise noted.)
E--0 to 10 cm; light brownish gray (10YR 6/2) silt loam, grayish brown (10YR 5/2) moist; weak thin platy structure; soft, friable, nonsticky and nonplastic; many fine roots; many fine pores; neutral (pH 7.2); abrupt smooth boundary. (0 to 10 cm thick)
Btn--10 to 38 cm; grayish brown (10YR 5/2) clay loam, dark grayish brown (10YR 4/2) moist; strong coarse columnar prismatic structure parting to strong medium blocky; very hard, very firm, very sticky and very plastic; gray (10YR 6/1) silt coating on tops of columns; many distinct clay films on faces of peds; common fine roots; common fine pores; moderately alkaline (pH 8.0); gradual wavy boundary (18 to 30 cm thick)
Bkn--38 to 64 cm; light yellowish brown (10YR 6/4) clay loam, yellowish brown (10YR 5/4) moist; moderate medium blocky structure; hard; firm, moderately sticky and moderately plastic; common fine roots; common fine pores; 5 percent gravel and 2 percent cobbles; common soft masses of calcium carbonate; violently effervescent; strongly alkaline (pH 9.0); gradual boundary. (10 to 25 cm thick)
BCkn--64 to 89 cm; brown (10YR 5/3) gravelly clay loam, brown (10YR 4/3) moist; massive; slightly hard, friable, moderately sticky and moderately plastic; common fine roots; common fine pores; 15 percent gravel and 5 percent cobbles; many soft masses of calcium carbonate; violently effervescent; strongly alkaline (pH 8.6); gradual boundary. (15 to 38 cm thick)
C--89 to 152 cm; pale brown (10YR 6/3) gravelly clay loam, brown (10YR 5/3) moist; massive; slightly hard, friable, moderately sticky and moderately plastic; few fine roots; few fine pores; 25 percent gravel and 2 percent cobbles; finely disseminated calcium carbonate; strongly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Ravalli County, Montana; 260 meters south of the NE corner of sec. 22, T6N, R20W.
RANGE IN CHARACTERISTICS:
Soil temperature - 5.0 to 8.0 degrees C.
Control section - 27 to 35 percent clay
Depth to secondary calcium carbonate accumulation - 22 to 40 cm
Exchangeable sodium percentage - less than 15 percent in more than one half of the lower part of the natric horizon
Note: Some pedons have an A horizon.
A horizon (when present):
Hue: 10YR, 7.5YR or 5YR; dry or moist
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3; dry or moist
Texture: loam or silt loam
Clay content: 15 to 25 percent
Rock fragments: 0 to 35 percent--0 to 10 percent gravel, 0 to 15 percent cobbles, 0 to 10 percent stones
Reaction: pH 6.6 to 7.8
E horizon:
Hue: 10YR, 7.5YR or 5YR; dry or moist
Value: 6 or 7 dry; 5 or 6 moist
Chroma: 2 or 3; dry or moist
Texture: loam or silt loam
Clay content: 15 to 25 percent
Rock fragments: 0 to 35 percent--0 to 10 percent gravel, 0 to 15 percent cobbles, 0 to 10 percent stones
Reaction: pH 6.6 to 7.8
Btn horizon:
Hue: 10YR, 7.5YR or 5YR; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3; dry or moist
Texture: clay loam
Clay content: 27 to 35 percent
Rock fragments: 0 to 15 percent gravel
Electrical conductivity: 0 to 8 mmhos/cm
Sodium adsorption ratio: 13 to 18
Reaction: pH 8.5 to 9.0
Bkn horizon:
Hue: 10YR, 7.5YR or 5YR; dry or moist
Value: 6 or 7 dry; 5 or 6 moist
Chroma: 3 or 4; dry or moist
Texture: clay loam or loam
Clay content: 18 to 30 percent
Rock fragments: 0 to 15 percent gravel
Calcium carbonate equivalent: 10 to 15 percent
Electrical conductivity: 0 to 8 mmhos/cm
Sodium adsorption ratio: 8 to 18
Reaction: pH 8.4 to 9.0
BCkn horizon:
Hue: 10YR, 7.5YR or 5YR; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 3 or 4; dry or moist
Texture: clay loam or loam
Clay content: 18 to 30 percent
Rock fragments: 0 to 15 percent--0 to 10 percent gravel, 0 to 5 percent cobbles
Calcium carbonate equivalent: 5 to 15 percent
Electrical conductivity: 0 to 8 mmhos/cm
Sodium adsorption ratio: 8 to 12
Reaction: pH 8.4 to 9.0
C horizon:
Hue: 10YR, 7.5YR or 5YR; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 3 or 4; dry or moist
Texture: loam or fine sandy loam
Clay content: 14 to 27 percent
Rock fragments: 0 to 35 percent--0 to 25 percent gravel, 0 to 10 percent cobbles
Calcium carbonate equivalent: 0 to 10 percent
Electrical conductivity: 0 to 8 mmhos/cm
Sodium adsorption ratio: 0 to 10
Reaction: pH 7.8 to 9.0
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - fan remnants, eroded fan remnants and outwash fans
Elevation - 900 to 1,500 meters
Slope - 0 to 45 percent
Parent material - alluvium, outwash or slope alluvium
Climate - cool with long cold winters, moist springs, moist falls, and warm dry summers
Mean annual precipitation - 330 to 430 mm
Mean annual air temperature - 3.5 to 7.5 degrees C.
Frost-free period - 90 to 125 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: Used as rangeland and irrigated cropland. Crops are wheat, barley, oats and alfalfa hay.
DISTRIBUTION AND EXTENT: Mountain valleys of western Montana. MLRA - 44A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Bitterroot Valley Area, Montana, 1914.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - 0 to 10 cm (E horizon);
Argillic horizon - 10 to 38 cm (Btn horizon);
Natric horizon - 10 to 64 cm (Btn, Bkn horizons); and
Particle-size control section - 10 to 38 cm (Btn horizon).
Ravalli soils have a frigid temperature regime and an ustic moisture regime.
Additional Information: 2/2013 - Based on climate data, the classification changed from Haplargidic Natrustalfs to Typic Natrustalfs.
National Cooperative Soil Survey
U.S.A.