LOCATION ALLWIT IDEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Typic Endoaquolls
TYPICAL PEDON: Allwit gravelly sandy loam under pasture on a south facing concave slope of 1 percent at an elevation of 4950 feet. When described on August 3, 1977 the soil was dry to 2 inches, moist from 2 to 22 inches, and saturated below 22 inches. (Colors are for dry soils unless otherwise noted.)
A--0 to 9 inches; grayish brown (10YR 5/2) gravelly sandy loam, very dark gray (10YR 3/1) moist; many fine prominent yellowish red (5YR 4/6) mottles, dark reddish brown (5YR 3/3) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many fine and very fine roots; 20 percent pebbles; neutral (pH 7.2); clear smooth boundary. (5 to 12 inches thick)
Bw--9 to 22 inches; brown (7.5YR 5/2) very gravelly sandy loam, dark brown (7.5YR 4/2) moist; many fine distinct strong brown (7.5YR 5/6) mottles, dark brown (7.5YR 4/4) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and very fine roots; 55 percent pebbles; neutral (pH 6.8); gradual smooth boundary. (10 to 15 inches thick)
C--22 to 60 inches; variegated extremely gravelly sand; single grain; loose; 60 percent pebbles and 20 percent cobbles; neutral (pH 6.6).
TYPE LOCATION: Fremont County, Idaho; approximately one mile east and three miles south of St. Anthony, about 2630 feet west and 660 feet south of the northeast corner of Section 19, T.7N., R. 41E.
RANGE IN CHARACTERISTICS:
Average summer soil temperature - 60 to 64 degrees F.
Depth to fluctuating watertable - +12 to 24 inches
Control section averages - Texture average: GRV-SL, GRX-SL
Mollic epipedon - 7 to 15 inches
A horizon
Value - 4 or 5 dry
Chroma - 1 through 3 dry and moist
Mottles - hue - 5YR or 7.5YR
Value - 4 or 5 dry, 3 or 4 moist
Chroma - 3 through 6 dry and moist
Quantity - few through many
Bw horizon
Hue - 10YR or 7.5YR
Value - 3 through 5 dry and moist
Chroma - 2 through 6 dry and moist
Mottles - distinct and prominent with the same range in colors as the matrix
Texture - GRV-SL, GR-SL
C horizon
Texture: GRX-S, GRV-SL
Percent pebbles - 40 to 65 percent
Percent cobbles - 0 to 25 percent
Other features - common distinct and prominent mottles are present in some pedons
COMPETING SERIES: This is the Irim, Poronto and Swampcreek series. Irim and Poronto soils have 18 to 35 percent clay in the particle-size control section and do not have loose sand and gravel above 40 inches. Swampcreek soils have secondary carbonates at a depth of 20 to 40 inches.
GEOGRAPHIC SETTING: Allwit soils are on nearly level and slightly concave swales of low river terraces. They formed in alluvium from mixed sources. Slopes are 0 to 2 percent. Elevations are 4800 to 5200 feet. The average annual precipitation is 12 to 16 inches; the average annual air temperature is 41 to 46 degrees F.; and the frost-free season is 80 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Eginbench and St. Anthony series. Eginbench soils formed in eolian deposits over sandy alluvium, are somewhat poorly drained, and are located on higher river terraces. St. Anthony soils are well drained and are located on the higher ground adjacent to Allwit soils.
DRAINAGE AND PERMEABILITY: Poorly drained; very slow runoff or ponded; moderately rapid permeability to 22 inches, rapid below. These soils are occasionally flooded for brief periods from April through June. Soil water table is controlled by the river level.
USE AND VEGETATION: Allwit soils are used for pasture and wetland wildlife habitat. Common vegetation includes Kentucky bluegrass and sedges.
DISTRIBUTION AND EXTENT: Southeastern Idaho; MLRA's 11, 13. These soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Fremont County, Idaho, 1989.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 9 inches (A horizon).
Cambic horizon - The zone from 9 to 22 inches (Bw horizon).
Particle-size control section - The zone from 10 to 40 inches (Bw and part of the C horizon).