LOCATION MILLHI IDEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Vertic Natrargids
TYPICAL PEDON: Millhi gravelly silt loam--on a 14 percent smooth northeast-facing slope in rangeland at 5,700 feet elevation. (Colors are for dry soils unless otherwise stated. When described on September 22, 1982 the soil was dry to a depth of 9 inches and moist below.)
A--0 to 2 inches; brown (10YR 5/3) gravelly silt loam, very dark grayish brown (10YR 3/2) moist; weak very fine and fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and few fine roots; many very fine interstitial pores; 30 percent pebbles on surface; 25 percent pebbles in horizon; moderately alkaline (pH 8.0); clear wavy boundary. (0 to 5 inches thick)
E--2 to 4 inches; pale brown (10YR 6/3) gravelly silt loam, dark brown (10YR 3/3) moist; weak very fine and fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and few fine and medium roots; many very fine interstitial pores; 15 percent pebbles; moderately alkaline (pH 8.0); abrupt wavy boundary. (0 to 4 inches thick)
Btn--4 to 9 inches; pinkish gray (7.5YR 6/2),((brown (7.5YR 4/4) crushed)) clay, dark yellowish brown (10YR 3/4) moist; moderate very fine and fine prismatic structure parting to strong fine and medium subangular blocky; very hard, very firm, moderately sticky and moderately plastic; common very fine and few fine, medium and coarse roots; few very fine interstitial pores; many distinct clay films in pores and on faces of peds; 2 percent pebbles; skeletans on tops and sides of peds at upper boundary; moderately alkaline (pH 8.0); clear wavy boundary. (3 to 10 inches thick)
Btkn1--9 to 13 inches; pale brown (10YR 6/3) clay loam, dark brown (10YR 4/3) moist; moderate very fine and fine subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine and few fine and medium roots; common very fine interstitial pores; distinct clay films in pores and on faces of peds; 2 percent pebbles; slightly effervescent; strongly alkaline (pH 8.8); clear wavy boundary. (3 to 10 inches thick)
Btkn2--13 to 17 inches; pale brown (10YR 6/3) clay loam, dark brown (10YR 4/3) moist; moderate very fine and fine prismatic structure parting to strong very fine, fine and medium subangular blocky; hard, friable, moderately sticky and moderately plastic; common very fine and few fine roots; few very fine interstitial pores; many distinct clay films in pores and on faces of peds; slightly effervescent; strongly alkaline (pH 8.8); clear wavy boundary. (3 to 10 inches thick)
2Bkny--17 to 27 inches; brownish yellow (10YR 6/6) and pale brown (10YR 6/3) clay, very dark grayish brown (10YR 3/2) and olive brown (2.5Y 4/4) moist; strong very fine angular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; few very fine roots; few very fine interstitial pores; 5 percent cobbles; common masses of gypsum; slightly effervescent; moderately alkaline (pH 8.2); clear wavy boundary. (8 to 14 inches thick)
2Bny1--27 to 48 inches; light yellowish brown (2.5Y 6/4) gravelly clay, light olive brown (2.5Y 5/4) moist; strong very fine angular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine interstitial pores; 15 percent pebbles; 10 percent cobbles; common masses of gypsum; moderately alkaline (pH 8.2); clear wavy boundary. (18 to 23 inches thick)
2Bny2--48 to 60 inches; pale yellow (2.5Y 7/4) clay, light olive brown (2.5Y 5/4) moist; strong very fine angular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine interstitial pores; moderately alkaline (pH 8.2).
TYPE LOCATION: Lemhi County, Idaho; about 1.5 miles west of Tendoy, Idaho; about 2,300 feet north and 400 feet east of the southwest corner of sec. 30, T. 19 N., R. 24 E. Latitude - 44 degrees, 56 minutes, 48 seconds North; Longitude - 113 degrees, 40 minutes, 00 seconds West.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 43 to 46 degrees F
Control section; percent clay - 35 to 60 percent
Rock fragments - 5 to 30 percent
Perched water table - 0 to 12 during February to April
Depth to natric - 0 to 9 inches
Depth to gypsic material - 16 to 38 inches
Depth to secondary lime - 4 to 16 inches
A horizon
value - 5 or 6 dry, 2 through 4 moist
E horizon
Value - 5 through 7 dry, 3 through 5 moist
Chroma - 2 through 4 dry and moist
Texture - L, GR-L, GR-SIL, SIL
Rock fragments - 5 to 30 percent
Btn horizon
Hue - 7.5YR or 10YR
Value - 4 through 7 dry, 3 though 6 moist
Chroma - 2 through 4 dry and moist
Texture - C, CL, GR-CL
Reaction - Moderately through strongly alkaline
Btkn horizon
Hue - 7.5 or 10YR
Value - 5 through 8 dry, 3 through 6 moist
Chroma - 2 through 6 dry and moist
Texture - GR-C, CL, GR-CL, C
2Bny horizon
Hue - 5Y, 2.5Y, 7.5YR, or 10YR
Value - 6 through 8 dry, 3 through 6 moist
Chroma - 2 through 8 dry and moist
Texture - C, GR-C, CL
Rock fragments - 0 to 30 percent
Reaction - Moderately through strongly alkaline
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Millhi soils are on lacustrine terraces and foothills and have slopes of 2 to 35 percent. The soils formed in lacustrine sediments. Elevations are 3,900 to 5,000 feet. The climate is cold and moist in winter and spring, and dry in summer. Average annual precipitation is 7 to 10 inches. Average annual temperature is 42 to 45 degrees F. Frost free period is 75 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cronks, Lacrol, Perreau, Venum, and Zer soils. Cronks and Venum soils are on foothills and mountains, and have clayey-skeletal control sections. Cronks soils have mollic epipedons. Perreau and Zer soils are on terraces and foothills. Perreau soils have fine-loamy control sections. Zer soils have loamy-skeletal control sections. Lacrol soils are on north and east aspects in concave positions on foothills and have mollic epipedons.
DRAINAGE AND PERMEABILITY: Moderately well drained, medium to very rapid runoff, very slow permeability.
USE AND VEGETATION: Rangeland. Vegetation is mainly Wyoming big sagebrush and bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: East-central Idaho. These soils are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Lemhi County, Idaho, 1999.
REMARKS: Diagnostic features recognized in this pedon are:
Ochric epipedon
Natric horizon - The zone from 4 to 17 inches (Bt and Btk horizons).
Linear extensibility is estimated to be 6 to 8 cm in the upper meter.
The gypsic material does meet the gypsum requirement to qualify as a gypsic horizon.
The particle-size control section is the natric horizon which is the zone from 4 to 17 inches (Btn and Btkn horizons).
Some pedons have EB or E/B horizons.