LOCATION PETTY MTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Andic Haplocryepts
TYPICAL PEDON: Petty gravelly ashy loam, forested. (Colors are for dry soil unless otherwise noted.)
0i--0 to 3 inches; undecomposed and slightly decomposed forest litter.
Bw--3 to 15 inches; light yellowish brown (10YR 6/4) gravelly ashy loam, dark yellowish brown (10YR 4/4) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine, fine, and medium roots; many very fine and fine pores; 20 percent gravel; moderately acid (pH 6.0); clear smooth boundary. (7 to 14 inches thick)
2E--15 to 27 inches; very pale brown (10YR 7/4) very gravelly coarse sandy loam, yellowish brown (10YR 5/4) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; common very fine, fine, and medium roots; many very fine and fine pores; 35 percent gravel and 5 percent cobbles; moderately acid (pH 6.0); gradual wavy boundary. (10 to 16 inches thick)
2E and Bt--27 to 39 inches; E part (70 percent) is very pale brown (10YR 7/4) very gravelly coarse sandy loam, yellowish brown (10YR 5/4) moist; B part (30 percent) is strong brown (7.5YR 5/6) fine sandy loam lamellae 1/8 to 1/2 inch thick, brown (7.5YR 4/4) moist; weak medium subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; few very fine, fine, and medium roots; common very fine and fine pores; 45 percent gravel and 10 percent cobbles; slightly acid (pH 6.2); gradual wavy boundary. (10 to 18 inches thick)
2C--39 to 60 inches; very pale brown (10YR 7/4) extremely gravelly coarse sandy loam, yellowish brown (10YR 5/4) moist; massive; slightly hard, very friable, nonsticky and nonplastic; few very fine and fine roots; few very fine and fine pores; 50 percent gravel and 15 percent cobbles; slightly acid (pH 6.4).
TYPE LOCATION: Missoula County, Montana; 400 feet west and 300 feet south of the NE corner of sec. 4, T. 10 N., R. 23 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 39 to 44 degrees F.
Moisture control section - between 8 and 24 inches
NOTE: Some pedons have a thin, discontinuous E. horizon at the surface.
Bw horizon - Hue: 10YR or 7.5YR
Value: 5 or 6 dry; 3 or 4 moist
Chroma: 4 or 6
Clay content: 7 to 15 percent
Rock fragments: 15 to 35 percent--0 to 10 percent cobbles and stones; 15 to 25 percent gravel
Reaction: pH 5.6 to 6.5
Moist bulk density: less than 1.0 g/cc
Acid oxalate extractable Al + 1/2 Fe: more than 1.0
2E horizon - Hue: 10YR or 7.5YR
Value: 6 or 7 dry; 5 or 6 moist
Chroma: 3, 4, or 6
Texture: coarse sandy loam with more than half the sand fraction coarse or very coarse sand
Clay content: 5 to 15 percent
Rock fragments: 35 to 55 percent--5 to 10 percent cobbles and stones; 30 to 45 percent gravel
Reaction: pH 5.6 to 6.5
2E and Bt horizon - Hue: E part 10YR or 7.5YR
Value: E part 6 or 7, B part 5 or 6 dry; E part 4 or 5, B part 4 or 5 moist
Chroma: 3, 4, or 6
Clay content: 5 to 15 percent, fine sandy loam lamellae has less than 3 percent clay increase
Rock fragments: 35 to 60 percent--5 to 15 percent cobbles and stones; 30 to 45 percent gravel
Reaction: pH 5.6 to 6.5
2C horizon - Hue: 10YR or 7.5YR
Value: 6 or 7 dry; 5 or 6 moist
Chroma: 3, 4, or 6
Texture: coarse sandy loam or loamy coarse sand
Clay content: 5 to 15 percent
Rock fragments: 45 to 70 percent--5 to 40 percent cobbles and stones; 30 to 55 percent gravel
Reaction: pH 5.6 to 6.5
COMPETING SERIES:
Ashworth (MT) - has horizons of secondary carbonate accumulation.
Buhrig (WA) - has a lithic contact at 20 to 40 inches; has a xeric moisture regime.
Buttoncreek (WA) - has a xeric moisture regime; does not have a 2E horizon.
Devore (WA) - has a lithic contact at 20 to 40 inches; has a xeric moisture regime.
Finney (WA) - has a lithic contact at 40 to 60 inches.
Gatewall (WA) - has a xeric moisture regime; has compact glacial till at 18 to 30 inches; does not have a 2E horizon.
Holloway (MT) - has an albic horizon; has less than 50 percent coarse or very coarse sand.
Hun (ID) - does not have horizon containing lamellae.
Moses (WA) - has a paralithic contact of quartz monzonite at 20 to 40 inches.
Myerscreek (WA) - has a lithologic discontinuity of compact glacial till mainly below 30 inches.
Otwin (WA) - has a lithic contact at 20 to 40 inches; has a xeric moisture regime.
Phillcher (MT) - does not have horizon containing lamellae; has a mean annual soil temperature of 35 to 38 degrees F.
Prouty (WA) - has a paralithic contact at 20 to 40 inches.
Remmel (WA) - has a xeric moisture regime; does not have a 2E horizon.
Rubycreek (ID) - does not have horizon containing lamellae; does not have a 2E horizon.
Rumsey (MT) - has horizons of secondary carbonate accumulation.
Surgh (WA) - has a lithic contact of gneiss at 40 to 60 inches.
Sweetbutte (WA) - has a lithic contact at 40 to 60 inches; has a xeric moisture regime.
Waldbillig (MT) - has an albic horizon; has a very hard 2E and Bt horizon.
GEOGRAPHIC SETTING:
Landform- broad ridgetops and mountain slopes.
Elevation - 4,500 to 7,000 feet.
Slope - 8 to 80 percent.
Parent material - volcanic ash over colluvium and glacial drift derived mainly from granite and gneiss.
Climate - cool with cold winters and moist springs.
Mean annual precipitation - 35 to 50 inches, much of which falls as snow or as spring rain.
Mean annual temperature - 37 to 42 degrees F.
Frost-free period - 30 to 70 days.
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; moderately rapid permeability.
USE AND VEGETATION: Petty soils are used for timber production and watersheds and as wildlife habitat. The native vegetation is subalpine fir, western larch, Douglas-fir, Engelmann spruce, and lodgepole pine with an understory of twinflower, blue huckleberry, queencup beadlily, rusty menziesia, and grouse whortleberry.
DISTRIBUTION AND EXTENT: Petty soils are moderately extensive in western Montana and northern Idaho.
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 mineral soil surface to 7 inches (Bw horizon); a cambic horizon from 27 to 39 inches (2E and Bt horizon); a soil layer from the mineral soil surface to 15 inches that has a moist bulk density of 1.0 g/cc or less (Bw horizon); a particle-size control section from 10 to 40 inches (Bw, 2E, 2E and Bt, 2C horizons). Petty soils have a cryic temperature regime and a udic moisture regime.
The 3/2008 description reflects a change in classification from Loamy-skeletal, mixed, superactive Andic Eutrocryepts to Loamy-skeletal, mixed, superactive Andic Haplocryepts due to revision of the cryepts great groups and subgroups. The competing series section was not updated and should be reviewed after all the cryepts have been re-classified.