LOCATION MCBIGGAM ID

Established Series
Rev. PFB-HBM-MEJ-GHL
01/2011

MCBIGGAM SERIES

The McBiggam series consists of very deep, well-drained soils that formed in loess overlying material weathered from basalt. McBiggam soils are on basalt plains and have slopes of 2 to 8 percent. Permeability is slow. The mean annual precipitation is about 14 inches, and the mean annual air temperature is about 41 degrees F.

TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Typic Palexerolls

TYPICAL PEDON: McBiggam silt loam--on a 4 percent slope at an elevation of 5,400 feet in rangeland. When described on July 21, 1980, the soil was moist below 10 inches. (Colors are for dry soil unless otherwise stated.)

A1--0 to 3 inches; very dark grayish brown (10YR 3/2) silt loam, very dark brown (10YR 2/2) moist; moderate very fine granular structure; soft, friable, slightly sticky and slightly plastic; many very fine, fine, and medium roots; many very fine interstitial pores; about 10 percent pebble-sized cinders; neutral (pH 6.7); clear smooth boundary. (3 to 7 inches thick)

A2--3 to 10 inches; dark brown (10YR 3/3), silt loam, very dark brown (10YR 2/2) moist; moderate fine and medium granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine, fine and medium roots; many very fine interstitial pores; about 10 percent pebble-sized cinders; neutral (pH 6.6) clear smooth boundary. (5 to 9 inches thick)

BA--10 to 15 inches; brown (10YR 4/3) silt loam, very dark grayish brown (10YR 3/2) moist; strong fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine, fine and medium roots; many very fine, fine and medium tubular pores; neutral (pH 7.0); clear smooth boundary. (2 to 7 inches thick)

Bt--15 to 26 inches; light yellowish brown (10YR 6/4) silty clay loam, brown (10YR 4/3) moist; strong fine and medium angular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine, fine and medium roots; common very fine and fine tubular pores; few faint clay films on faces of peds and lining pores; few thin bleached sand and silt grains on faces of peds; about 5 percent cobbles and 5 percent pebbles at lower boundary; neutral (pH 7.0); abrupt smooth boundary. (5 to 14 inches thick)

2Btb--26 to 36 inches; brown (7.5YR 4/2) silty clay, dark brown (7.5YR 3/4) moist; strong medium and coarse prismatic structure; very hard, very firm, very sticky and moderately plastic; common very fine and fine roots; few very fine tubular pores; many continuous slickensides on faces of peds and many distince clay films lining pores; slightly alkaline (pH 7.4); abrupt wavy boundary. (7 to 16 inches thick)

2Btkb--36 to 46 inches; brown (7.5YR 4/4) silty clay, dark brown (7.5YR 3/4) moist; strong medium angular blocky structure; very hard, very firm, very sticky and moderately plastic; few very fine and fine roots; common very fine tubular pores; many continuous slickensides on faces of peds and common distinct clay films lining pores; strongly effervescent on faces of peds, slightly effervescent in matrix; slightly alkaline (pH 7.8); clear wavy boundary. (10 to 17 inches thick)

2Bkb--46 to 80 inches; brown (7.5YR 5/4) silty clay loam, brown (7.5YR 4/4) moist; massive; hard, firm, moderately sticky and moderately plastic; few fine roots; few fine tubular pores; nearly continuous pinkish white (7.5YR 8/2) lime coating on ped faces and in pores; strongly effervescent; moderately alkaline (pH 8.2).

TYPE LOCATION: Blaine County, Idaho, about 2 miles north and 18 miles east of Carey; 2,500 feet east and 400 feet north of the southwest corner, sec. 15, T. 1 S. R. 24 E.

RANGE IN CHARACTERISTICS:

Depth to buried subsoil - 22 to 36 inches
Mean annual soil temperature - 42 to 45 degrees F
Reaction - Slightly acid to slightly alkaline
Thickness of mollic epipedon - 10 to 15 inches
Clay content - upper 20 inches of argillic horizon averages 27 to 35 percent

A horizons
Value - 3 to 5 dry, 2 or 3 moist
Chroma - 2 or 3 moist or dry

Bt horizons
Value - 4 to 6 dry
Chroma - 3 or 4 moist or dry
Percent clay content - 26 to 32
Percent rock fragments - 5 to 10

2Btb and 2Btkb horizons
Value - 3 to 5 dry, 3 or 4 moist
Chroma - 2 to 4 moist or dry
Percent clay content - 32 to 50
Reaction - neutral to slightly alkaline

2Bkb horizon
Value - 5 to 8 dry, 4 or 5 moist
Chroma - 2 to 4 moist or dry
Percent clay content - 30 to 40
Percent coarse fragments - 0 to 5
Reaction - slightly to moderately alkaline

COMPETING SERIES: There are no other soils in this family.

GEOGRAPHIC SETTING: McBiggam soils are on basalt plains. Slopes range from 2 to 8 percent. Elevation ranges from 5,300 to 5,600 feet. The soil formed in loess and underlying material weathered from basalt. The average annual precipitation is 12 to 16 inches, most of which falls as snow and early spring rains. The average annual air temperature is about 40 to 43 degrees F. The frost-free season is 70 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: They are the Bancroft, Mccarey, Molyneux, and Pedleford soils. Bancroft soils have calcic horizons above 40 inches. McCarey soils have calcic horizons and are moderately deep. Molyneux soils have base saturation of 50 to 75 percent in the upper 75 cm. Pedleford soils have calcic horizons and have more than 35 percent rock fragments in the control section. Bancroft, McCarey, and Pedleford soils occur on basalt plains. Molyneux soils occur on fan terraces.

DRAINAGE AND PERMEABILITY: Well-drained. Slow to medium runoff and slow permeability.

USE AND VEGETATION: Mainly used for rangeland. Vegetation is mountain big sagebrush, rabbitbrush, Idaho fescue, prairie junegrass, lupine, and phlox.

DISTRIBUTION AND EXTENT: Small extent. South-central Idaho.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: Blaine County, Idaho, 1985.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Mollic epipedon: from the soil surface to approximately 15 inches (A1, A2, and BA).

Argillic horizon: the zone from 15 to 46 inches (Bt, 2Btb, and 2Btkb horizons)

The upper 20 inches of the argillic horizon averages 27 to 35 percent clay.

Argillic horizon does not decrease by as much as 20 percent of the maximum clay content within a vertical distance of 1.5 meters and has a hue redder than 10YR.

National Cooperative Soil Survey
U.S.A.