LOCATION ORO FINO                MT

Established Series
Rev. DES-JJU-RJS
05/2011

ORO FINO SERIES

The Oro Fino series consists of very deep, well drained soils that formed in colluvium or slope alluvium derived from gneiss and schist. These soils are on hills, ridges, pediments, cuestas and mountains. Slopes are 2 to 45 percent. Mean annual precipitation is about 16 inches and mean annual air temperature is about 38 degrees F.

TAXONOMIC CLASS: Fine-loamy, mixed, superactive Calcic Argicryolls

TYPICAL PEDON: Oro Fino gravelly loam, native grassland (colors are for dry soil unless otherwise noted).

A1--0 to 4 inches; dark grayish brown (10YR 4/2) gravelly loam, very dark brown (10YR 2/2) moist; weak medium platy structure parting to weak fine granular; soft, very friable, nonsticky and slightly plastic; many fine roots; many fine vesicular and tubular pores; 20 percent gravel; neutral (pH 6.8); clear smooth boundary.

A2--4 to 10 inches; dark grayish brown (10YR 4/2) gravelly loam, very dark brown (10YR 2/2) moist; moderate very coarse prismatic structure parting to weak medium subangular blocky; hard, friable, slightly sticky and slightly plastic; common fine roots; common fine irregular pores, and few fine vesicular and tubular pores; 15 percent gravel; neutral (pH 6.8); clear smooth boundary. (combined thickness of A1, A2 horizons - 7 to 15 inches)

Bt--10 to 22 inches; brown (10YR 5/3) gravelly sandy clay loam, brown (10YR 4/3) moist; strong very coarse prismatic structure parting to moderate fine subangular blocky; hard, firm, slightly sticky and moderately plastic; common fine roots; common fine irregular pores, and few fine vesicular and tubular pores; common faint clay skins as bridges between sand grains; 15 percent gravel; neutral (pH 7.2); clear smooth boundary. (10 to 14 inches thick)

Bk1--22 to 34 inches; light gray (10YR 7/2) gravelly loam, light brownish gray (10YR 6/2) moist; massive; slightly hard, friable, nonsticky and nonplastic; common fine roots; 30 percent gravel; many soft masses of calcium carbonate; violently effervescent; moderately alkaline (pH 7.9); abrupt wavy boundary. (12 to 15 inches thick)

Bk2--34 to 42 inches; brown (10YR 5/3) very gravelly sandy loam, brown (10YR 5/3) moist; massive; soft, very friable, nonsticky and nonplastic; few fine roots; common fine irregular pores; 40 percent gravel; common soft masses of calcium carbonate; strongly effervescent; slightly alkaline (pH 7.6); clear wavy boundary. (7 to 10 inches thick)

Bk3--42 to 60 inches; brown (10YR 5/3) extremely gravelly loamy sand, brown (10YR 4/3) moist; single grain; loose, nonsticky and nonplastic; few fine roots in cracks; few fine irregular pores; 60 percent gravel; common soft masses of calcium carbonate; strongly effervescent; slightly alkaline (pH 7.6).

TYPE LOCATION: Madison County, Montana; Sweetwater Divide; approximately 2,400 feet north and 1,000 feet west of the SE corner of sec. 13, T. 8S, R. 7W.

RANGE IN CHARACTERISTICS:
Soil temperature - 38 to 42 degrees F.
Mollic epipedon thickness - 7 to 15 inches
Depth to calcic horizon - 15 to 30 inches
Depth to sandy or sandy-skeletal material - 35 to 60 inches
Note: Some pedons may have a BC horizon below 40 inches.

A1, A2 horizons
Hue: 7.5YR or 10YR; dry or moist
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 2 or 3; dry or moist
Texture: loam, sandy loam or coarse sandy loam
Clay content: 10 to 25 percent
Rock fragments: 10 to 30 percent gravel
Reaction: pH 6.6 to 7.8

Bt horizon
Hue: 7.5YR or 10YR; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 3 or 4; dry or moist
Texture: sandy clay loam, clay loam or loam
Clay content: 20 to 35 percent
Sand content: more than 35 percent fine sand or coarser
Rock fragments: 15 to 35 percent gravel
Reaction: pH 6.6 to 7.8

Bk1 horizon
Hue: 7.5YR or 10YR; dry or moist
Value: 6 to 8 dry; 5 to 7 moist
Chroma: 2 to 6; dry or moist
Texture: loam, sandy loam or coarse sandy loam
Clay content: 10 to 20 percent
Rock fragments: 15 to 35 percent gravel
Calcium carbonate equivalent: 10 to 20 percent
Reaction: pH 7.4 to 8.4

Bk2 horizon
Hue: 7.5YR or 10YR; dry or moist
Value: 5 to 7 dry; 5 or 6 moist
Chroma: 2 to 6; dry or moist
Texture: loam, sandy loam or coarse sandy loam
Clay content: 10 to 20 percent
Rock fragments: 15 to 45 percent gravel
Calcium carbonate equivalent: 5 to 20 percent
Reaction: pH 7.4 to 8.4

Bk3 horizon
Hue: 7.5YR or 10YR; dry or moist
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 to 6; dry or moist
Texture: sand or loamy sand
Clay content: 5 to 10 percent
Rock fragments: 35 to 60 percent gravel
Calcium carbonate equivalent: 5 to 10 percent
Reaction: pH 7.4 to 8.4

BC horizon (where present)
Hue: 7.5YR or 10YR; dry or moist
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 to 6; dry or moist
Texture: sand or loamy sand
Clay content: 5 to 10 percent
Rock fragments: 30 to 60 percent gravel
Calcium carbonate equivalent: 5 to 10 percent
Reaction: pH 7.4 to 8.4

COMPETING SERIES:
Accola (MT) - does not have sandy or sandy-skeletal material at depths of less than 60 inches
Elispring (MT) - are moderately deep to a lithic contact
Gebson (CO) - does not have sandy or sandy-skeletal material at depths of less than 60 inches
Glentivar (CO) - does not have sandy or sandy-skeletal material at depths of less than 60 inches
Madigan (MT) - are moderately deep to a lithic contact
Michelson (MT) - does not have sandy or sandy-skeletal material at depths of less than 60 inches
Monida (ID) - have a xeric soil moisture regime
Morset (CO) - does not have sandy or sandy-skeletal material at depths of less than 60 inches
Northorn (UT) - have an udic soil moisture regime
Philipsburg (MT) - does not have sandy or sandy-skeletal material at depths of less than 60 inches

GEOGRAPHIC SETTING:
Landform - hills, ridges, cuestas, pediments and mountains
Elevation - 5,200 to 7,800 feet
Slope - 2 to 45 percent
Parent material - colluvium or slope alluvium derived from gneiss and schist
Climate - long, cold winters; moist springs; short summers.
Mean annual precipitation - 15 to 19
Mean annual air temperature - 34 to 40 degrees F.
Frost-free period - 30 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Adel, Nieman, and Poin series. Adel soils have a mollic epipedon more than 40 mm thick and lack an argillic horizon. Nieman and Poin soils have bedrock at depths of less than 20 inches.

DRAINAGE AND PERMEABILITY: Well drained; moderate permeability to about 42 inches and moderately rapid below.

USE AND VEGETATION: Oro Fino soils are used mainly for rangeland; some areas are used for irrigated and nonirrigated small grains and hay. Potential native vegetation is mainly Idaho fescue, bluebunch wheatgrass, lupine, and big sagebrush.

DISTRIBUTION AND EXTENT: Oro Fino soils are moderately extensive in the foothills of south western Montana. MLRA - 43B, 44B, 46.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.

SERIES ESTABLISHED: Madison County, Montana, 1983.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 10 inches (A1, A2 horizons)
Argillic horizon - from 10 to 22 inches (Bt horizon)
Calcic horizon - from 22 to 60 inches (Bk1, Bk2, Bk3 horizons)
Sandy-skeletal material - from 42 to 60 inches (Bk3 horizon)
Particle-size control section - from 10 to 22 inches (Bt horizon)

Oro Fino soils have a cryic temperature regime and an ustic moisture regime.

ADDITIONAL DATA: Soil interpretations records - MT0405 and MT8066.

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National Cooperative Soil Survey
U.S.A.