LOCATION PACKMO IDEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Xeric Haplocalcids
TYPICAL PEDON: Packmo gravelly loam--on a 3 percent slightly convex, northeast aspect at 6,560 feet elevation in rangeland. (Colors are for dry soil unless otherwise noted. When described on June 5, 1985, the soil was moist throughout.)
A--0 to 3 inches; brown (10YR 5/3) gravelly loam, dark brown (10YR 3/3) moist; moderate medium angular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine and common medium and coarse roots; many very fine and fine irregular pores; 15 percent pebbles; neutral (pH 7.2); clear smooth boundary. (2 to 5 inches thick)
Bw--3 to 10 inches; light yellowish brown (10YR 6/4) gravelly loam, dark brown (10YR 4/3) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine and common medium and coarse roots; common very fine and fine irregular and tubular pores; 30 percent pebbles; slightly alkaline (pH 7.4); gradual wavy boundary. (6 to 10 inches thick)
2Bk--10 to 13 inches; light yellowish brown (10YR 6/4) very gravelly sandy loam, brown (10YR 5/3) moist; weak fine subangular blocky structure; slightly hard, very friable; slightly sticky and slightly plastic; many very fine and common fine roots; common very fine and fine tubular pores; 50 percent pebbles, 5 percent cobbles; lime coatings 1 to 3 mm thick on undersides of some coarse fragments; slightly alkaline (pH 7.5); gradual wavy boundary. (0 to 10 inches thick)
2Bkq1--13 to 18 inches; pale brown (10YR 6/3) extremely gravelly sandy loam, brown (10YR 5/3) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine and few medium roots; common very fine tubular pores; 60 percent pebbles, 10 percent cobbles; lime and silica coatings 1 to 3 mm thick on undersides of coarse fragments; strongly effervescent; moderately alkaline (pH 8.2); gradual wavy boundary. (3 to 12 inches thick)
2Bkq2--18 to 20 inches; very pale brown (10YR 7/3) extremely gravelly loam, very pale brown (10YR 7/4) moist; massive; slightly hard, firm, slightly sticky and slightly plastic; few very fine and fine roots; common very fine irregular and tubular pores; 35 percent pebbles, 30 percent cobbles; lime and silica coatings and pendants 1 to 5 mm thick on undersides and some sides of coarse fragments; discontinuous pockets and layers of weakly cemented material; violently effervescent; moderately alkaline (pH 8.3); gradual wavy boundary. (1 to 10 inches thick)
2Bkq3--20 to 38 inches; multicolored extremely gravelly sandy loam; single grain; loose; few very fine and fine roots; common medium irregular pores; 60 percent pebbles, 15 percent cobbles; lime and silica coatings 1 to 5 mm thick on undersides and some sides of coarse fragments; strongly effervescent; moderately alkaline (pH 8.1); clear wavy boundary. (3 to 12 inches thick)
2Bkq4--38 to 40 inches; very pale brown (10YR 8/2) extremely gravelly sandy loam, very pale brown (10YR 7/3) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; common very fine and fine irregular and tubular pores; 50 percent pebbles, 30 percent cobbles; lime and silica coatings and pendants 1 to 5 mm thick on undersides and some sides of coarse fragments; discontinuous pockets and layers of weakly cemented material; violently effervescent; moderately alkaline (pH 8.3); abrupt wavy boundary. (2 to 12 inches thick)
2Bkq5--40 to 60 inches; multicolored extremely gravelly loamy coarse sand; single grain; loose; few very fine and fine roots; common medium irregular pores; 45 percent pebbles, 30 percent cobbles, 10 percent stones; lime and silica coatings and pendants 1 to 5 mm thick on undersides and some sides of rock fragments; strongly alkaline (pH 8.5).
TYPE LOCATION: Custer County, Idaho; approximately 3 miles north west of Chilly Buttes, about 1,800 feet north and 1,600 feet west from the southeast corner of section 21, T.9N., R.21E. Latitude - 44 degrees, 05 minutes, 35 seconds north Longitude - 113 degrees, 58 minutes, 42 seconds west
RANGE IN CHARACTERISTICS:
The soil moisture control section is dry for one-half to three-fourths of the time when the soil temperature is above 41 degrees F; aridic bordering on xeric.
Average summer soil temperature - 59 to 63 degrees F.
Average annual soil temperature - 41 to 45 degrees F
Control section - Percent total clay: 10 to 18
Carbonate clay - 5 to 10 percent
Rock fragments: 45 to 85 percent
Depth to carbonates - 10 to 13 inches
Depth to the calcic horizon (2Bkq2 horizon) is 10 to 20 inches. The calcic horizon has 5 to 15 percent calcium carbonate equivalent; the presence of pendants on coarse fragments is characteristic.
A horizon
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 2 to 4 dry or moist
Reaction - neutral or slightly alkaline
Bw horizon
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 3 or 4 dry or moist
Texture - GR-L, GRV-SL
Rock fragments - 30 to 55 percent
Reaction - neutral or slightly alkaline
2Bk horizon
Value - 4 or 5 moist
Chroma - 2 to 4 dry or moist
Texture - GR-FSL, GRV-SL, GRX-COSL
Coarse fragments - 30 to 70 percent
Reaction - slightly or moderately alkaline
2Bkq horizon
Value - 6 through 8 dry, 3 through 7 moist
Chroma - 2 or 3 dry, 3 or 4 moist
Texture - GRV-L, GRX-L, GRX-SL, GRX-LCOS, GRV-SL, GRX-LS
Rock fragments - 50 to 85 percent
Reaction - slightly to strongly alkaline
Clay content is 5 to 18 percent decreasing with depth
COMPETING SERIES: These are the Misfire, Holinrock and Zer soils. Misfire soils lack the discontinuous weakly cemented material. Holinrock soils are moderately deep. Zer soils are calcareous to the soil surface.
GEOGRAPHIC SETTING: Packmo soils are on outwash fans and fan terraces. These soils formed in mixed alluvium. Slopes are 1 to 20 percent. Elevations are 5,400 to 6,800 feet. The climate is cold and moist in winter and spring and dry in summer. Average annual precipitation is 8 to 11 inches. Average summer temperature is 60 to 62 degrees F. Average annual temperature is 39 to 43 degrees F. Frost-free period is 45 to 75 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bock, Derwell, Whiteknob, and the competing Zer soils. Bock soils are on outwash fans and fan terraces and have a mollic epipedon and less than 35 percent coarse fragments. Derwell soils are on outwash fans and fan terraces and have less than 35 percent coarse fragments in the control section. Whiteknob soils are on outwash fans and fan terraces and have sandy-skeletal control sections. Zer soils are on mountains and are calcareous to the surface.
DRAINAGE AND PERMEABILITY: Well drained. Slow runoff; moderate permeability.
USE AND VEGETATION: Rangeland and minor areas of irrigated hayland. The natural vegetation is Wyoming big sagebrush and bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: East-central Idaho. These soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Custer County, Idaho, 1999.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 3 inches (A horizon).
Cambic horizon - The zone from 3 to 10 inches (Bw horizon).
Calcic horizon - The zone from 18 to 60 inches (the 2Bkq2, 2Bkq3, 2Bkq4, and 2Bkq5 horizons).
Particle-size control section - The zone from 10 to 40 inches (the 2Bk, 2Bkq1, 2Bkq2, 2Bkq3, and the 2Bkq4 horizons).