LOCATION IDMONTON ID

Established Series
IRD. WGH/TDT
09/2018

IDMONTON SERIES

The Idmonton series consists of very deep, somewhat poorly drained soils formed in mixed alluvium with loess influence. Idmonton soils are on fan remnants, stream terraces and flood plains and have slopes of 0 to 2 percent. The mean annual precipitation is about 560 mm and the mean annual air temperature is about 4.4 degrees C.

TAXONOMIC CLASS: Fine-loamy, mixed, superactive Aquic Cumulic Haplocryolls

TYPICAL PEDON: Idmonton silty clay loam on a stream terrace with 1 percent slope at an elevation of 1,900 meters. (Colors are for dry soil unless otherwise noted.)

A1--0 to 10 cm; dark gray (10YR 4/1) silty clay loam, black (10YR 2/1) moist; moderate fine granular structure; hard, friable, moderately sticky and moderately plastic; many very fine and fine roots; many fine tubular pores; 5 percent gravel; neutral (pH 7.0); gradual smooth boundary.

A2--10 to 25 cm; dark gray (10YR 4/1) clay loam, black (10YR 2/1) moist; strong medium subangular blocky structure parting to strong fine subangular blocky; hard, friable, moderately sticky and moderately plastic; many very fine and fine roots; many fine tubular and irregular pores; 5 percent gravel; slightly alkaline (pH 7.6); gradual smooth boundary. (Combined thickness of the A horizons is 25 to 56 cm)

AB--25 to 41 cm; grayish brown (10YR 5/2) clay loam, very dark gray (10YR 3/1) moist; moderate fine subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common fine roots; common fine tubular pores; 5 percent gravel; slightly alkaline (pH 7.6); gradual smooth boundary. (0 to 30 cm thick)

2Bw1--41 to 86 cm; grayish brown (10YR 5/2) sandy clay loam, very dark grayish brown (10YR 3/2) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; common fine roots; common fine tubular pores; 5 percent gravel; slightly alkaline (pH 7.6); abrupt smooth boundary. (15 to 50 cm thick)

2Bw2--86 to 122 cm; grayish brown (10YR 5/2) sandy clay loam, very dark gray (10YR 3/1) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; common fine roots; common fine tubular pores; common medium prominent irregular dark brown (7.5YR 3/4) moist iron and manganese masses; 5 percent gravel; slightly alkaline (pH 7.6); abrupt smooth boundary. (10 to 45 cm thick)

3C--122 to 152 cm; mixed colors, predominantly light gray (10YR 7/1) extremely gravelly sand, dark gray (5Y 4/1) moist; single grain; loose, nonsticky and nonplastic; common fine roots; many fine irregular pores; 85 percent gravel; slightly alkaline (pH 7.6).

TYPE LOCATION: Clark County, Idaho; about 10.8 km south and 1.0 km west of Kilgore, Idaho; about 133 meters north and 644 meters east of the southwest corner of section 6, T.11 N., R.39 E.; Idmon USGS topographic quadrangle; latitude 44 degrees, 18 minutes, and 16.9 seconds N. and longitude 111 degrees, 54 minutes, 21.2 seconds W., NAD83.

RANGE IN CHARACTERISTICS:
Mollic epipedon thickness: 50 to 125 cm
Depth to redoximorphic features (iron/manganese concentrations): 50 to 100 cm
Particle size control section average rock fragments: 0 to 10 percent gravel
Particle size control section average clay content: 20 to 35 percent
Reaction: neutral to slightly alkaline
Soil moisture regime: xeric
Mean annual soil temperature: 3.3 to 6.1 degrees C.
Mean summer soil temperature: 11.1 to 14.4 degrees C.
Depth to water table: 45 to 95 cm during May and June and below about 100 cm for the rest of the year.

A horizons
Value: 3 to 5 dry, 2 or 3 moist
Chroma: 1 or 2 dry or moist
Rock fragments: 0 to 5 percent gravel
Texture: CL, SCL

AB horizon
Value: 3 to 6 dry, 2 to 4 moist
Chroma: 1 to 3 dry or moist
Rock fragments: 0 to 5 percent gravel
Texture: CL, SCL

2Bw horizons
Hue: 10YR or 2.5Y
Value: 5 to 7 dry, 3 to 5 moist
Chroma 1 to 3 dry, 1 to 4 moist
Texture: SCL CL
Rock fragments: 5 to 10 percent gravel

3C horizons
Hue: 10YR to 5Y
Value: 6 or 7 dry, 3 or 4 moist
Chroma 1 to 3 dry, 1 to 4 moist
Texture: S, LS, with 35 to 85 percent gravel

COMPETING SERIES: This is the Menbar series. Menbar soils are slighty to moderately alkaline throughout and are typically effervescent.

GEOGRAPHIC SETTING:
Landscape: Mountains
Landform: fan remnants, stream terraces and flood plains
Elevation: 1,830 to 2,012 meters
Slope: 0 to 2 percent
Parent material: mixed alluvium with loess influence
Mean annual air temperature: 2.2 to 4.4 degrees C.
Mean annual precipitation: 406 to 610 mm
Frost free period: 45 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Fourme, Alex, Kilgore, Seemore and Longway soils. All of these soils are on similar landforms. Fourme soils are loamy-skeletal, well drained and located on higher slightly convex fan remnants and stream terraces. Alex soils are fine-loamy over sandy or sandy skeletal, moderately well drained and located on stream terraces. Kilgore soils are poorly drained and are located on flood plains and lower terraces. Seemore soils are poorly drained and located on flood plains, intermediate stream terraces and fan remnants. Longway soils are well drained and found on higher, linear surfaces of fan remnants and stream terraces.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class: somewhat poorly drained
Runoff: low
Saturated hydraulic conductivity: moderately high in the upper part to very high in the lower part
Flooding frequency and duration: Frequent flooding for brief periods in the spring.

USE AND VEGETATION:
Major uses: These soils are used for rangeland, hayland and wildlife habitat.
Dominant native vegetation: mountain brome, Idaho fescue, prairie junegrass, slender wheatgrass, columbian needlegrass, arrowleaf balsamroot, geranium, lupine and mountain big sagebrush.

DISTRIBUTION AND EXTENT:
Distribution: Eastern Idaho, MLRA 13.
Extent: the series is not extensive

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Portland, Oregon

SERIES PROPOSED: Clark County Area, Idaho, 2018.

REMARKS:
Diagnostic horizons and soil characteristics recognized in this pedon are:
Mollic epipedon: from a depth of 0 to 122 cm
Particle size control section: from a depth of 25 to 100 cm
Irregular decrease in organic-carbon content: present from 41 to 152 cm
Soil temperature regime: cryic
Soil moisture regime: xeric
Redox features occur a 86 cm.

National Cooperative Soil Survey
U.S.A.