LOCATION DARKBULL ID+UTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Sodic Xeric Haplocalcids
TYPICAL PEDON: Darkbull loam--rangeland. On a 1 percent smooth slope, N.W. aspect, 4,700 feet elevation. (Profile was dry above 22 inches and moist below. Colors are for air-dry soil unless otherwise noted. This profile was described October 23, 1978.)
A1--0 to 3 inches; pale brown (10YR 6/3) loam, dark grayish brown (10YR 4/2) moist; moderate medium subangular blocky structure parting to weak fine and very fine granular; soft, very friable, slightly sticky and slightly plastic; many fine and very fine roots; many very fine tubular pores; 10 percent gravel; slightly effervescent (1 percent calcium carbonate); moderately alkaline (pH 8.2); abrupt smooth boundary. (3 to 5 inches thick)
A2--3 to 4 inches; pale brown (10YR 6/3) loam, dark brown (10YR 3/3) moist; weak very thick platy structure parting to weak fine subangular blocky; soft, very friable, slightly sticky and slightly plastic; many very fine roots; many fine tubular pores; 5 percent gravel; slightly effervescent (3 percent calcium carbonate); strongly alkaline (pH 8.6); abrupt smooth boundary. (1 to 4 inches thick)
Bw--4 to 7 inches; pale brown (10YR 6/3) loam, brown (10YR 5/3) moist; moderate coarse and medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine roots; many very fine tubular pores; 5 percent gravel; strongly effervescent (10 percent calcium carbonate); strongly alkaline (pH 9.0); clear wavy boundary. (2 to 4 inches thick)
Bk1--7 to 13 inches; very pale brown (10YR 7/3) loam, brown(10YR 5/3) moist; weak coarse and medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; common very fine roots; many very fine tubular pores; 5 percent gravel; violently effervescent (20 percent calcium carbonate); strongly alkaline (pH 9.0); clear smooth boundary. (5 to 8 inches thick)
Bk2--13 to 20 inches; very pale brown (10YR 7/3) sandy loam, brown (10YR 5/3) moist; massive; slightly hard, very friable, nonsticky and nonplastic; common very fine roots; many very fine tubular pores; 5 percent gravel; violently effervescent (16 percent calcium carbonate); strongly alkaline (pH 8.6); abrupt wavy boundary. (6 to 10 inches thick)
2Bk3--20 to 22 inches; white (10YR 8/2) very gravelly sandy loam, light brown (7.5YR 6/4) moist; very hard, firm, nonsticky and nonplastic; few very fine roots; 55 percent gravel; silica pendents on underside of gravel; violently effervescent (16 percent calcium carbonate); strongly alkaline (pH 8.6); abrupt discontinuous boundary. (0 to 2 inches thick)
2C1--22 to 28 inches; very pale brown (10YR 7/3) very gravelly loamy sand, brown (10YR 5/3) moist; single grain; loose; 60 percent gravel; strongly effervescent (13 percent calcium carbonate equivalent); moderately alkaline (pH 8.4); clear smooth boundary. (4 to 8 inches thick)
2C2--28 to 60 inches; very pale brown (10YR 7/3) very gravelly sand, brown (10YR 5/3) moist; single grain; loose; 60 percent gravel; strongly effervescent (8 percent calcium carbonate); moderately alkaline (pH 8.2).
TYPE LOCATION: Cassia County, Idaho; about 7 miles northeast of Malta, Idaho, about 375 feet east and 925 feet north of the southwest corner of sec. 1, T. 13S., R. 27E. Latitude - 42 degrees, 18 minutes, 56 seconds North; Longitude - 113 degrees, 15 minutes, 11 seconds West.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 47 to 50 degrees F.
Depth to calcic horizon - 6 to 10 inches
Thickness of calcic horizon - 12 to 20 inches
Depth to very gravelly layer - 17 to 23 inches
Particle-size control section
Rock fragment content - 35 to 70 percent gravel, cobbles, and stones Clay content - 6 to 15 percent
A horizon
Value - 6 or 7 dry, 3 or 4 moist
Chroma - 2 or 3 dry or moist
Calcium carbonate equivalent - 0 to 5 percent
Bw horizon
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 2 through 4 dry or moist
Texture - L, SIL, GR-SIL, or GR-L
Rock fragment content - 0 to 30 percent gravel
Calcium carbonate equivalent - 5 through 15 percent
Bk horizon
Value - 6 through 8 dry, 4 through 7 moist
Chroma - 2 through 4 dry or moist
Texture - L through GRV-SL
Rock fragment content - 5 to 55 percent gravel
Calcium carbonate equivalent - 10 through 30 percent
Reaction - moderately through very strongly alkaline
Sodium absorption ratio - 10 to 35
2C horizons
Texture - GRV-LS, GRX-LS, GRV-S, CBV-S
Rock fragment content - 35 to 65 percent gravel, cobbles, and stones Reaction - moderately to strongly alkaline
Sodium absorption ratio - 20 to 30
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Darkbull soils are on terraces. Slopes range from 0 to 30 percent. The soils formed in mixed alluvium at elevations of 4,400 to 6,000 feet. The climate is cold and moist in the winter and hot and dry in the summer. Average annual precipitation ranges from 8 to 12 inches. The average summer temperature is 60 to 72 degrees F., and the average annual temperature is 45 to 48 degrees F. The frost-free period is about 95 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Declo, Escalante, Mellor, and Strevell soils. Declo, Escalante, and Strevell soils have a coarse-loamy control section. Mellor soils have a natric horizon. They are all on fan terraces.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderate permeability in the upper part of the profile and very rapid below.
USE AND VEGETATION: Darkbull soils are used for rangeland and irrigated cropland. Natural vegetation is Wyoming big sagebrush, bottlebrush squirreltail, and bluebunch wheatgrass. Irrigated crops are alfalfa, wheat, barley, and sugar beets.
DISTRIBUTION AND EXTENT: Darkbull soils are of large extent in southern Idaho and northern Utah.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Box Elder County, Utah, 1985.
REMARKS: The transition from the overlying loamy layers to the underlying very gravelly sand is greater than 12.5 centimeters.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to 7 inches (A1, A2, and Bw horizons)
Calcic horizon - the zone from 7 to 22 inches (Bk1, Bk2, and 2Bk3 horizons)
Sodic feature - the zone from 13 to 40 inches (Bk2, 2Bk3, 2C1, and part of the 2C2 horizons)
Particle-size control section - 10 to 40 inches (Bk1, Bk2, 2Bk3, 2C1, and part of the 2C2 horizons)