LOCATION PURDAM IDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Haploxeralfic Argidurids
TYPICAL PEDON: Purdam silt loam - on a nearly level lava plain at 2,500 feet elevation in cropland. (Colors are for air-dry soil unless otherwise noted.)
Ap1--0 to 4 inches; light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; weak fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; many very fine vesicular pores; neutral (pH 6.7); clear wavy boundary.
Ap2--4 to 10 inches; light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; many fine tubular pores; neutral (pH 6.9); abrupt smooth boundary. (Combined A horizon - 6 to 12 inches thick.)
Bt1--10 to 13 inches; pale brown (10YR 6/3) silty clay loam, brown (10YR 4/3) moist; weak medium prismatic structure parting to moderate medium subangular blocky; hard, firm, sticky and plastic; few very fine, fine, and medium roots; many fine tubular pores; many distinct brown (10YR 5/3) clay films on faces of peds and in pores; neutral (pH 7.2); clear wavy boundary. (3 to 16 inches thick)
Bt2--13 to 19 inches; pale brown (10YR 6/3) silt loam, dark grayish brown (10YR 4/2) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine roots; many fine tubular pores; few faint brown clay films on faces of peds and in pores; few weakly cemented nodules or krotovinas (durinodes); calcium carbonate occurs as fine veins; very slightly effervescent; moderately alkaline (pH 8.2); clear wavy boundary. (0 to 15 inches thick)
Btkq--19 to 24 inches; very pale brown (10YR 7/3) silt loam, brown (10YR 4/3) moist; massive; hard, firm, slightly sticky and slightly plastic; few fine and medium roots; common fine tubular pores; 30 to 50 percent of volume consists of weakly cemented nodules or cicada krotovinas (durinodes); calcium carbonate occurs as fine veins; slightly effervescent; moderately alkaline (pH 8.3); clear smooth boundary. (4 to 13 inches thick)
Bkqm--24 to 38 inches; very pale brown (10YR 7/3) strongly cemented duripan, brown (10YR 4/3) moist; massive breaking to strong medium platy laminations; cemented; very hard, very firm; strongly effervescent; moderately alkaline (pH 8.3); abrupt wavy boundary. (3 to 20 inches thick)
2C--38 to 60 inches; stratified loam, sandy loam, and sand; slightly effervescent; moderately alkaline (pH 8.1).
TYPE LOCATION: Canyon County, Idaho; about 4 miles southwest of Caldwell; 320 feet south and 2,050 feet east of the NW corner of section 11, T.3N., R.4W.; USGS Marsing Quadrangle; (Latitude - 43 degrees, 37 minutes, 00 seconds N. and Longitude - 116 degrees, 47 minutes, 02 seconds W.).
RANGE IN CHARACTERISTICS:
Depth to bedrock - more than 60 inches
Average annual soil temperature - 47 to 56 degrees F.
Depth to duripan - 20 to 40 inches
Depth to calcium carbonate - 12 to 28 inches
Particle-size control section - 20 to 32 percent clay; 0 to 5 percent gravel
Moisture control section - moist less than 90 consecutive days when the soil temperature is greater than 47 degrees F.
A or Ap horizon
Value - 5 through 7 dry, 3 or 4 moist
Chroma - 2 or 3 dry or moist
Bt horizon or Btkq
Value - 5 or 6 dry, 3 through 5 moist
Chroma - 2 through 6 dry or moist
Texture - SIL or SICL
Clay content - 24 to 32 percent
Reaction - neutral through moderately alkaline
Bkq horizon (when present)
Value - 6 through 8 dry, 4 through 6 moist
Chroma - 2 through 4 dry or moist
Texture - L, SIL, FSL or VFSL
Rock fragment content - 0 to 10 percent gravel
Clay content - 12 to 22 percent
Calcium carbonate equivalent - 8 to 30 percent
Durinodes - 5 to 30 percent
Reaction - slightly alkaline or moderately alkaline
Bkqm horizon
Thickness of first silica lamination - 1 to 12 mm
Calcium carbonate equivalent - 15 to 40 percent
Texture - VFSL, L, SIL
COMPETING SERIES: There are no competing series. The Cherry Spring soils are similar, but have a Bt horizon that contains 15 to 35 percent fine sand and coarser.
GEOGRAPHIC SETTING: Purdam soils are on plug domes (buttes), lava flow lobes and troughs on lava plains and shield volcanoes and on dissected terraces in valleys. Elevations are 2,000 to 5,000 feet. Slopes are commonly less than 8 percent, but range up to 30 percent. The soils formed in silty alluvium from loess and weathered volcanic ash over medium or moderately coarse-textured alluvium from igneous materials. The average annual precipitation is 8 to 12 inches, including up to 2 feet of snow. Average annual temperature is 45 to 54 degrees F. The frost-free season is 100 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Jenness, Power, Vickery, Sebree, and Sluka soils. Jenness soils lack a Bt horizon and a duripan. Power soils lack a duripan. Sebree soils have more than 15 percent exchangeable sodium in the Bt horizons. Sluka and Vickery soils lack a Bt horizon. These soils are on landscape positions similar to Purdam soils.
DRAINAGE AND PERMEABILITY: Well drained; medium to very slow runoff; moderately slow permeability.
USE AND VEGETATION: Purdam soils are used mainly for irrigated cropland. A few areas are used for rangeland. Crops are small grains, corn, sugar beets, alfalfa, potatoes, and onions; some is in pasture. Vegetation in the potential natural plant community is Wyoming big sagebrush, bluebunch wheatgrass, Thurber needlegrass, and Sandberg bluegrass.
DISTRIBUTION AND EXTENT: Southwestern and south-central Idaho; MLRA 11. The soil is extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Gem County Area, Idaho, 1962.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 10 inches (Ap horizons)
Argillic horizon - the zone from 10 to 24 inches (Bt and Btkq horizons)
Calcic horizon - the zone from 19 to 38 inches (Btkq and Bkqm horizons)
Duripan - the zone from 24 to 38 inches (Bkqm horizon strongly cemented)
Particle-size control section - the zone from 10 to 24 inches
Soil moisture regime - aridic bordering xeric
The classification of this pedon has been revised as of 4/00 from fine-silty, mixed, mesic Haploxerollic Durargids to fine-silty, mixed, superactive, mesic Haploxeralfic Argidurids based on revisions to Soil Taxonomy.
The term silty alluvium used in this series concept infers a localized influence on the mixed loess and weathered ash mantle by overland flow of running water.
Geographic setting - terms used throughout MLRA 11 to identify the setting of this soil are quire varied although all equate to the same landscape. There will be further investigation from an MLRA project level as to the accepted terms for use.
The pedon description was revised 4/00 to agree with the original taxonomic unit description in the Canyon County Area, Idaho soil survey.