LOCATION BENNING IDEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Pachic Calcixerolls
TYPICAL PEDON: Benning silt loam, irrigated cropland; on a 2 percent slope at 6,050 feet elevation. When described on November 10, 1988, the soil was dry throughout. (Color is for dry soil unless otherwise noted.)
Ap--0 to 7 inches; dark grayish brown (10YR 4/2) silt loam, very dark gray (10YR 3/1) moist; weak fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine roots; common very fine and few fine irregular and few fine tubular pores; 5 percent gravel; slightly effervescent (8 percent calcium carbonate equivalent), disseminated lime; moderately alkaline (pH 7.9); abrupt smooth boundary. (7 to 12 inches thick)
Bk1--7 to 18 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate coarse prismatic structure parting to moderate very fine subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; many very fine and few fine roots; common very fine and few fine, medium and coarse tubular pores; 10 percent gravel; slightly effervescent (10 percent calcium carbonate equivalent), few fine irregularly shaped soft lime masses and disseminated lime; moderately alkaline (pH 7.9); clear smooth boundary. (7 to 15 inches thick)
Bk2--18 to 28 inches; grayish brown (10YR 5/2) silty clay loam, very dark gray (10YR 3/1) moist; moderate medium prismatic structure parting to moderate very fine and fine subangular blocky; slightly hard, friable, moderately sticky and moderately plastic; many very fine and few fine roots; common very fine and few fine and medium tubular pores; 10 percent gravel; strongly effervescent (8 percent calcium carbonate equivalent), common fine irregularly shaped soft lime masses and disseminated lime; moderately alkaline (pH 8.0); gradual smooth boundary. (8 to 12 inches thick)
Bk3--28 to 37 inches; dark grayish brown (10YR 4/2) gravelly silty clay loam, very dark gray (10YR 3/1) moist; moderate coarse prismatic structure parting to moderate fine subangular blocky; hard, friable, moderately sticky and moderately plastic; common very fine and few fine roots; common very fine and few fine and medium tubular pores; 15 percent gravel; strongly effervescent (9 percent calcium carbonate equivalent), common fine irregularly shaped soft lime masses and disseminated lime; moderately alkaline (pH 8.0); gradual wavy boundary. (5 to 10 inches thick)
Bk4--37 to 49 inches; grayish brown (10YR 5/2) silt loam, dark grayish brown (10YR 4/2) moist; common medium prominent brown (7.5YR 5/4) mottles; massive; slightly hard, very friable, slightly sticky and slightly plastic; common very fine roots; common very fine and few fine tubular and few very fine irregular pores; 10 percent gravel; strongly effervescent (25 percent calcium carbonate equivalent), common medium irregularly shaped soft lime masses and disseminated lime; moderately alkaline (pH 8.0); clear smooth boundary. (5 to 12 inches thick)
2Bkq--49 to 60 inches; brown (10YR 5/3) extremely gravelly silt loam, dark grayish brown (10YR 4/2) moist; common medium distinct brown (7.5YR 5/4) mottles; massive; slightly hard, very friable, slightly sticky and slightly plastic; common very fine roots; common very fine tubular and few fine and medium irregular pores; 55 percent gravel and 15 percent cobbles; many distinct weak silica coats on all sides of coarse fragments; violently effervescent (35 percent calcium carbonate equivalent), common medium irregularly shaped soft lime masses and disseminated lime; moderately alkaline (pH 8.1)
TYPE LOCATION: Bear Lake County, Idaho; about 1/2 mile east of Georgetown; about 2,700 feet east and 2,700 feet south of the northwest corner of sec. 7, T.11 S., R.44 E. Latitude - 42 degrees, 28 minutes, 51.3 seconds north. Longitude - 111 degrees, 21 minutes, 26.1 seconds west.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 40 to 45 degrees F
Thickness of mollic epipedon - 20 to 42 inches
Depth to secondary lime - 5 to 12 inches
Depth to calcic horizon - 20 to 40 inches
Calcium carbonate equivalent in calcic horizon - 15 to 35 percent
Reaction - slightly or moderately alkaline
Absent in some pedons - relic mottles at depths of 25 to 50 inches
Particle size control section
Texture - SIL, SICL or GR-SICL
Clay - 20 to 33 percent
Rock fragments - 5 to 25 percent
Ap horizon
Value - 3 through 5 dry, 2 or 3 moist
Chroma - 1 or 2 dry or moist
Rock fragments - 0 to 15 percent
Effervescence - slight through strong
Calcium carbonate equivalent - 5 to 15 percent
Reaction - slightly or moderately alkaline
Bk horizons
Value - 4 or 5 dry, 3 or 4 moist
Chroma - 1 through 3 dry or moist
Texture - SIL, SICL, GR-SICL
Rock fragments - 5 to 25 percent
Calcium carbonate equivalent - 5 to 35 percent
Reaction - moderately alkaline
2Bkq horizon
Value - 4 or 5 dry, 3 or 4 moist
Chroma - 1 through 3 dry or moist
Rock fragments - 60 to 80 percent
Calcium carbonate equivalent - 15 to 35 percent
Reaction - moderately alkaline
The 2Bkq is absent in some pedons
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Benning soils are on fan remnants. Slopes range from 1 to 4 percent. Elevations range from 5,900 to 7,250 feet. These soils formed in mixed alluvium with some loess influence. The average annual precipitation ranges from 13 to 18 inches, the average annual air temperature is 39 to 44 degrees F and the frost free season is 70 to 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arbone, Bezzant, Hondoho, Iphil (T), Rexburg and Watkins Ridge soils. Arbone soils have a coarse-loamy particle-size control section. Arbone, Hondoho and Rexburg soils lack lime in the surface layer. Bezzant and Hondoho soils have a loamy-skeletal control section. Iphil and Rexburg soils have a coarse-silty particle-size control section. Watkins Ridge soils are not pachic. Rexburg and Iphil soils are on loess covered fan remnants above Benning soils. Arbone and Watkins Ridge soils are on smooth to slightly concave slopes near the middle of fan remnants. Bezzant and Hondoho soils occur on terrace breaks and in and near old stream channels.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately slow permeability.
USE AND VEGETATION: Benning soils are used for irrigated and nonirrigated cropland. Typical crops consist of small grains and alfalfa. The potential natural vegetation is Mountain big sagebrush, bluebunch wheatgrass and sod-forming grasses.
DISTRIBUTION AND EXTENT: Southeastern Idaho. This series is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Bear Lake County, Idaho, 2008.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Pachic epipedon - the zone from the surface to 37 inches (Ap, Bk1, Bk2 and Bk3 horizons)
Calcic horizon - the zone from 37 to 60 inches (Bk4 and 2Bkq horizons)
Particle-size control section - the zone from 10 to 40 inches (part of the Bk1, Bk2, Bk3 and part of the Bk4 horizons)