LOCATION GRASSVALLEY MTEstablished Series
TAXONOMIC CLASS: Fine, illitic, frigid Typic Haploxeralfs
TYPICAL PEDON: Grassvalley silty clay loam, cultivated. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 9 inches; pinkish gray (7.5YR 6/2) silty clay loam, brown (7.5YR 4/2) moist; moderate fine and medium subangular blocky structure; hard, firm, sticky, and plastic; many very fine roots; many very fine pores; neutral (pH 6.8); abrupt smooth boundary. (6 to 10 inches thick)
Bt1--9 to 13 inches; light reddish brown (5YR 6/3) clay, reddish brown (5YR 4/3) moist; strong medium angular blocky structure; very hard, very firm, very sticky, and very plastic; common fine roots; many very fine pores; common thin clay films on faces of peds and in pores; neutral (pH 7.2); gradual wavy boundary. (3 to 6 inches thick)
Bt2--13 to 21 inches; light reddish brown (5YR 6/4) clay, reddish brown (5YR 4/4) moist; strong moderate and coarse angular blocky structure; very hard, very firm, very sticky, and very plastic; common very fine roots; common very fine pores; common thin clay films on faces of peds and in pores; mildly alkaline (pH 7.4); gradual wavy boundary. (6 to 10 inches thick)
Btk--21 to 28 inches; pink (5YR 7/3) clay, reddish brown (5YR 5/4) moist; strong fine angular blocky structure; very hard, very firm, very sticky, and very plastic; common very fine roots; common very fine pores; few thin clay films on faces of peds and in pores; common fine soft masses of lime; violently effervescent; moderately alkaline (pH 8.2); gradual wavy boundary. (4 to 10 inches thick)
BC--28 to 37 inches; pink (5YR 7/3) clay, reddish brown (5YR
5/4) moist; weak coarse angular blocky structure parting to 1/8- to 1/2-inch-thick varves; hard, firm, sticky, and plastic; few very fine roots; few very fine pores; strongly effervescent; moderately alkaline (pH 8.4); gradual wavy boundary. (6 to 12 inches thick)
C--37 to 60 inches; light reddish brown (5YR 6/4) clay, reddish brown (5YR 5/3) moist; massive; distinct 1/2- to 1-inch-thick varves; hard, firm, sticky, and plastic; strongly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Missoula County, Montana; 800 feet east and 100 feet south of the NW corner of sec. 14, T. 13 N., R. 20 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 45 to 47 degrees F.
Moisture control section - approximately between the depths of 4 and 12 inches.
Control section - 40 to 60 percent clay
Depth of Btk horizon - 15 to 26 inches
Ap horizon - Hue: 7.5YR or 10YR
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3
Clay content: 30 to 40 percent
Reaction: pH 6.6 to 7.8
Bt horizon - Hue: 5YR or 7.5YR
Value: 5, 6, or 7 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: clay or silty clay
Clay content: 40 to 60 percent
Reaction: pH 6.6 to 8.4
Btk horizon - Hue: 5YR or 7.5YR
Value: 6 or 7 dry; 5 or 6 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: clay or silty clay
Clay content: 40 to 60 percent
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 8.4
BC or C horizons - Hue: 5YR or 7.5YR
Value: 6, 7, or 8 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: clay, silty clay, or silty clay loam
Clay content: 35 to 60 percent
Reaction: pH 7.4 to 8.4
NOTE: The varves range from 1/8-inch to about 2 inches thick and limit penetration of roots and water
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Grassvalley soils are on lake terraces. Elevations are 3,200 to 3,800 feet. Slopes are 0 to 30 percent. These soils formed in glaciolacustrine deposits. The climate is characterized by long, cold winters; moist springs; and warm, dry summers. Mean annual precipitation is 11 to 14 inches, much of which fall as snow and as spring rain. Mean annual temperature is 43 to 45 degrees F. The frost-free period is 105 to 120 days.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; very slow permeability.
USE AND VEGETATION: Grassvalley soils are used for irrigated and dryland crops and as pastureland and rangeland. The potential native vegetation is bluebunch wheatgrass, rough fescue, needleandthread, and prairie junegrass.
DISTRIBUTION AND EXTENT: Grassvalley soils are of small extent in valleys of western Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Missoula County, Montana, 1985.
REMARKS: Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from the soil surface to 9 inches (Ap horizon); an argillic horizon from 9 to 28 inches (Bt1, Bt2, Btk horizons); a particle-size control section that is the argillic horizon from 9 to 28 inches (Bt1, Bt2, Btk horizons). Grassvalley soils have a frigid temperature regime and a xeric moisture regime.
ADDITIONAL DATA: Laboratory reference sample 79T7363-7365.