LOCATION POLATIS IDEstablished Series
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, frigid Xeric Haplocalcids
TYPICAL PEDON: Polatis silt loam, big sagebrush and grass. (Colors are for dry soil unless otherwise noted.)
A--0 to 3 inches; light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; weak thin platy structure that parts to weak very fine granular; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine vesicular pores; slightly effervescent; moderately alkaline (pH 8.2); abrupt smooth boundary. (0 to 4 inches thick)
Bw--3 to 7 inches; pale brown (10YR 6/3) silt loam, brown (10YR 4/3) moist; weak fine and medium subangular blocky structure that parts to weak very fine granular; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; common very fine and fine tubular pores; slightly effervescent; moderately alkaline (pH 8.2); clear wavy boundary. (0 to 7 inches thick)
Bk1--7 to 16 inches; light gray (10YR 7/2) silt loam, grayish brown (10YR 5/2) moist; strong fine and medium subangular blocky structure; hard, firm, slightly sticky and slightly plastic; common very fine and fine roots; common very fine and fine tubular pores; common firm cicada krotovinas; strongly effervescent; strongly alkaline (pH 8.6); gradual wavy boundary. (6 to 15 inches thick)
Bk2--16 to 26 inches; light gray (10YR 7/2) silt loam, grayish brown (10YR 5/2) moist; massive; hard, firm, slightly sticky and slightly plastic; few very fine and fine roots; common very fine and fine tubular pores; common firm cicada krotovinas; strongly effervescent; moderately alkaline (pH 8.4); abrupt wavy boundary. (5 to 15 inches thick)
Bk3--26 to 28 inches; light gray (10YR 7/2) silt loam, grayish brown (10YR 5/2) moist; massive; hard, firm, slightly sticky and slightly plastic; few very fine and fine roots; common very fine and fine tubular pores; common firm cicada krotovinas; strongly effervescent; moderately alkaline (pH 8.4); abrupt wavy boundary. (0 to 13 inches thick)
2R--28 inches; black (N 2/) basalt with coatings of calcium carbonate on surface and in cracks.
TYPE LOCATION: Bingham County, Idaho; about 2 miles north and 6 miles west of Moreland; 800 feet east and 125 feet south of the NW corner of sec. 11, T.2S., R.33E.
RANGE IN CHARACTERISTICS:
Depth to bedrock - 20 to 40 inches
Depth to calcic horizon - 3 to 15 inches
Mean annual soil temperature - 41 to 47 degrees F.
Mean summer soil temperature - 59 to 66 degrees F.
Soil moisture - usually dry, and are dry between depths of 4 and 12 inches for about 70 to 85 consecutive days in the summer
Reaction - slightly to strongly alkaline
Particle-size control section
Total clay content - 8 to 18 percent carbonate clay 5 to 15 percent, carbonatic free clay 3 to 10 percent
Fraction greater than 0.10 mm - 5 to 15 percent
A horizon
Value - 5 or 6 dry, 3 or 5 moist
Chroma of 2 or 3 moist and dry
Carbonates - where undisturbed the upper 3- to 6-inch layer is commonly noncalcareous; but where mixed to 7 inches, the soil is calcareous to the surface
Bw horizon
Value - 5 or 6 dry, 3 or 4 moist
Bk horizon
Value - 6 through 8 dry, 4 through 6 moist
Chroma - 2 or 3
Cicada krotovinas and nodules - 2 to 20 percent (very hard or hard, firm or very firm, dense, rounded or cylindrical)
Calcium carbonate equivalent - 15 to 30 percent
COMPETING SERIES: These are the Pancheri and Splittop series. Pancheri soils have bedrock at depths of 40 inches or more. Splittop soils have 20 to 27 percent total clay and 10 to 20 percent carbonate clay in the particle-size control section.
GEOGRAPHIC SETTING: Polatis soils formed in loess on level to rolling lava plains at elevations of 4,200 to 6,000 feet. Slopes range from 0 to 12 percent. The climate is semiarid, with dry summers. Mean annual temperature is 39 to 45 degrees F. and mean annual precipitation is 8 to 11 inches, including 2 to 4 feet of snowfall. Average frost-free season is 70 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Pancheri soils and the Tenno soils. Tenno soils are shallow and occur on ridges and around lava domes. Pancheri soils occur on similar positions.
DRAINAGE AND PERMEABILITY: Well-drained; medium or slow runoff; moderate permeability.
USE AND VEGETATION: Mainly rangeland or cultivated under irrigation for hay, pasture, sugar beets, potatoes, and small grains. The principal native plants are big sagebrush, Sandberg bluegrass, cheatgrass, bluebunch wheatgrass, and in places Indian ricegrass and rabbitbrush.
DISTRIBUTION AND EXTENT: Extensive in the loess-covered lava plains of southeastern Idaho.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Bingham County, Idaho, 1972.
REMARKS: The soils were classified formerly as Sierozems and later as Xerollic Calciorthids. The previous official series description states that some pedons have an SAR of up to 30. Those pedons with high sodium accumulations would now classify as Sodic Xeric Haplocalcids. There are also many pedons mapped as Polatis that contain 20 percent or more firm or very firm nodules. These pedons would now classify as Petronodic Haplocalcids. Diagnostic horizons and other features recognized in this pedon are:
Ochric epipedon
Calcic horizon - the zone from 7 to 28 inches (Bk1, Bk2 and Bk3 horizons).
Particle-size control section - the zone from 10 to 28 inches (part of the Bk1, the Bk2 and the Bk3 horizons).