LOCATION PACKHAM IDEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Xeric Haplocambids
TYPIFYING PEDON: Packham gravelly loam, pasture. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 6 inches; grayish brown (10YR 5/2) (brown, 10YR 5/3 crushed) gravelly loam, very dark grayish brown (10YR 3/2) moist; weak fine and very fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; many very fine and fine tubular pores; 30 percent rounded gravel; slightly alkaline (pH 7.4); gradual wavy boundary. (5 to 7 inches thick)
Bw1--6 to 12 inches; brown (10YR 5/3) gravelly loam, very dark grayish brown (10YR 3/2) (dark grayish brown, 10YR 4/2 crushed) moist; weak fine and medium granular structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; many very fine and fine tubular pores; 35 percent rounded gravel; slightly alkaline (pH 7.4); gradual wavy boundary. (3 to 8 inches thick)
Bw1--12 to 17 inches; brown (10YR 5/3) very gravelly loam, dark grayish brown (10YR 4/2) moist; weak fine subangular blocky structure parting to weak fine and medium granular; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; many very fine and fine tubular pores; 45 percent gravel; slightly alkaline (pH 7.4); gradual wavy boundary. (3 to 8 inches thick)
Bw3--17 to 24 inches; pale brown (10YR 6/3) very gravelly loam, dark grayish brown (10YR 4/2) moist; massive; hard, very friable, nonsticky and slightly plastic; common very fine and fine roots; many very fine and fine tubular pores; 60 percent rounded gravel; slightly alkaline (pH 7.8); clear wavy boundary. (3 to 8 inches thick)
2Bk1--24 to 32 inches; light brownish gray (10YR 6/2) extremely gravelly sandy loam, dark grayish brown (10YR 4/2) moist; massive; slightly hard, very friable, nonsticky and nonplastic; many very fine irregular pores; 80 percent rounded gravel; slightly effervescent; pebbles slightly coated with calcium carbonate on lower side; slightly alkaline (pH 7.8); clear wavy boundary. (6 to 12 inches thick)
2Bk2--32 to 60 inches; light brownish gray (10YR 6/2) very gravelly coarse sand; single grain; loose; many very fine irregular pores; slightly effervescent; slightly alkaline (pH 7.8).
TYPE LOCATION: Bingham County, Idaho; about 1.5 mile northwest of Blackfoot; 2,100 feet east and 1,000 feet north of the SW corner of sec. 24, T.2S., R.34E.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 43 to 46 degrees F.
Mean summer soil temperature - 59 to 66 degrees F.
Depth to secondary lime - 14 to 30 inches
Depth to the very gravelly coarse sand (2Bk2) - 20 to 35 inches
Particle-size control section
clay content - 12 to 18 percent
Rock fragments - 35 to 75 percent
A horizon
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 2 or 3 dry or moist
Bw horizon
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 2 through 4 dry or moist
Texture - GR-L, GRV-SL, GRV-L, GRX-L
Reaction - slightly or moderately alkaline
2Bk1 horizon
Texture - GRV-SL, GRV-L, GRX-L
Reaction - slightly to strongly alkaline
2Bk2 horizon
Texture - GRV-COS, GRV-LS, GRX-COS
Reaction - slightly to strongly alkaline
COMPETING SERIES: These are the Oreneva and Rinconflat series. Oreneva soils are moderately deep to bedrock. Rinconflat soils have 18 to 27 percent clay in the particle-size control section.
GEOGRAPHIC SETTING: Packham soils are on stream and fan terraces at elevations of 4,200 to 5,400 feet. Slopes range from 0 to 8 percent. The soils formed in mixed alluvium, dominantly from quartzite and sedimentary rock sources but with some rhyolitic, basaltic, and granitic influence. The climate is semiarid with dry summers. Mean annual temperature is 39 to 45 degrees F. and mean annual precipitation is 8 to 12 inches including 1 to 3 feet of snowfall. Average frost-free season is 80 to 125 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bannock and Hayeston soils. Bannock soils have mollic epipedons and are coarse-loamy over sandy or sandy-skeletal. Hayeston soils are coarse-loamy and do not have a cambic horizon. Both of these soils occur on similar landforms.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderate permeability in the upper part and very rapid in the lower part.
USE AND VEGETATION: Used primarily for irrigated pasture. The natural vegetation is mainly big sagebrush, rabbitbrush, cheatgrass, Sandberg bluegrass, three-tip sagebrush, and milk vetch.
DISTRIBUTION AND EXTENT: Eastern Idaho. The series is moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Bingham County, Idaho, 1972.
REMARKS: In updating this series it was assumed that the 2Bk did not have more than 5 percent by weight more secondary carbonates than the underlying horizons and therefore did not qualify as a calcic horizon. The AB horizon makes all the requirements of a mollic epipedon except for crushed dry color value. It is likely that some areas mapped as Packham are actually Mollisols.
Diagnostic horizons and other features recognized in this pedon are:
Ochric epipedon
Cambic horizon - the zone from 6 to 24 inches (Bw horizon).