LOCATION AJAX IDEstablished Series
TAXONOMIC CLASS: Fine, smectitic, calcareous, frigid Cumulic Vertic Endoaquolls
TYPICAL PEDON: Ajax silty clay -- on a 1 percent southwest slope at 3,780 feet elevation in pasture. (Colors are for dry soil unless otherwise noted. When described on July 2, 1990, the soil was moist from the surface to 36 inches and a water table was present at 36 inches).
Oi--0 to 1 inch; slightly decomposed roots. (0 to 1 inch thick)
A--1 to 5 inches; dark grayish brown (2.5Y 4/2) silty clay, very dark grayish brown (2.5Y 3/2) moist; strong medium subangular blocky structure; very hard, very firm, very sticky and very plastic; many very fine, fine, and medium roots; many fine irregular pores; slightly effervescent (less than 5 percent calcium carbonate equivalent); strongly alkaline (pH 8.6); clear smooth boundary. (4 to 13 inches thick)
Bg1--5 to 11 inches; dark grayish brown (2.5Y 4/2) silty clay loam, very dark grayish brown (2.5Y 3/2) moist many medium prominent dark yellowish brown (10YR 4/4) mottles; moderate medium subangular blocky structure parting to moderate medium platy; very hard, very firm, very sticky and very plastic; common medium roots; many fine irregular pores; slightly effervescent (less than 5 percent calcium carbonate equivalent); moderately alkaline (pH 8.4); clear smooth boundary. (5 to 15 inches thick)
Bg2--11 to 23 inches; dark grayish brown (2.5Y 4/2) silt clay loam, very dark grayish brown (2.5Y 3/2) moist; many medium prominent dark yellowish brown (10YR 4/4) and dark gray (10YR 4/1) redox concentrations and depletions; weak coarse angular blocky structure; very hard, very firm, very sticky and very plastic; slightly effervescent (less than 5 percent calcium carbonate equivalent); moderately alkaline (pH 8.0); clear smooth boundary. (8 to 27 inches thick)
Bg3--23 to 42 inches; olive gray (5Y 5/2) silty clay loam, black (5Y 2.5/2) moist; many medium prominent dark yellowish brown (10YR 4/4) and gray (10YR 5/1) redox concentrations and depletions; weak coarse subangular blocky structure; very hard, very firm, very sticky and very plastic; slightly effervescent (less than 5 percent calcium carbonate equivalent); slightly alkaline (pH 7.4); clear smooth boundary. (0 to 19 inches thick)
Cg--42 to 61 inches; olive gray (5Y 5/2) silty clay loam, dark olive gray (5Y 3/2) moist; massive; very hard, very firm, very sticky and very plastic; slightly alkaline (pH 7.6).
TYPE LOCATION: Lemhi County, Idaho; about 9 miles north of Salmon, Idaho, about 560 feet south and 1,250 feet east from the northwest corner of section 32, T.23N., R.22E. Latitude - 45 degrees, 17 minutes, 39 seconds North and Longitude - 113 degrees, 53 minutes, 31 seconds West.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 40 to 42 degrees F.
Control section - percent clay - 35 to 52
Calcium carbonate equivalent average - 1 to 5 percent
Depth to seasonal high water table - 6 to 18 inches in March through July
Mollic epipedon thickness - 24 to 60 inches
Linear extensibility - 6.0 to 7.0 cm between the mineral soil surface and 100 cm.
A horizon
Hue - 2.5Y or 10YR
Value - 3 through 5 dry, 2 or 3 moist
Chroma - 0 through 2 dry and moist
Reaction - moderately or strongly alkaline
Bg horizons
Hue - 5Y, 2.5Y or 10YR
Value - 3 through 5 dry, 2 or 3 moist
Chroma - 1 through 3 dry and moist
Reaction - slightly or moderately alkaline
Texture - SICL, SIC, C
Cg horizon
Hue - 5Y. 2.5Y or 10YR
Value 5 through 7 dry, 3 through 6 moist
Chroma - 1 through 4 dry and moist
Reaction - mildly or moderately alkaline
Texture - SICL, SIL
COMPETING SERIES: This is the Southam series. Southam soils have a water table above the soil surface throughout the growing season and are very poorly drained.
GEOGRAPHIC SETTING: Ajax series are on flood plains and stream terraces. These soils formed in fine textured alluvium. Slopes are 0 to 2 percent. Elevations are 3,700 to 5,200 feet. The climate is cold and moist in winter and spring, and dry in summer. Average annual precipitation is 9 to 12 inches. Average annual temperature is 42 to 44 degrees F. The frost-free period is 70 to 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bursteadt (T), Cowbone (T), Smout (T), Tohobit (T) and Zeegee (T) soils. These soils are on valley flats. Bursteadt soils are moderately well drained, have a calcic horizon, and have coarse-loamy particle-size control sections. Cowbone soils are poorly drained, have a calcic horizon and have coarse-loamy particle-size control sections. Smout soils are moderately well drained and have sandy-skeletal particle-size control sections. Tohobit soils are somewhat poorly drained, have a calcic horizon and have sandy-skeletal particle-size control sections. Zeegee soils are poorly drained and have fine-loamy particle-size control sections.
DRAINAGE AND PERMEABILITY: Poorly drained. Slow runoff. Slow permeability. This soil floods occasionally for brief periods in January through June.
USE AND VEGETATION: Mostly cultivated under flood irrigation for hay and pasture. The principle native vegetation is sedges, rushes and cinquefoil.
DISTRIBUTION AND EXTENT: East-central Idaho. These soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Lemhi County, Idaho, 1999.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from 1 to 42 inches (A, Bg1, Bg2 and Bg3 horizons)
Particle-size control section - the zone from 11 to 41 inches (the Bg2 horizon and part of the Bg3 horizon)