LOCATION IWICA                   ID

Established Series
Rev. DFA/CLM
01/2019

IWICA SERIES

The Iwica series consists of soils that are well drained and deep to a duripan that formed in alluvium from mixed sources. They are on terraces. Permeability is slow. Slopes range from 2 to 6 percent. The average annual precipitation is about 360 mm and the average annual temperature is about 6.1 degrees C.

TAXONOMIC CLASS: Fine, smectitic, frigid Calcic Pachic Argixerolls

TYPICAL PEDON: Iwica silt loam on a slope of 3 percent under native vegetation at 1,770 meter elevation. (Colors are for dry soil unless otherwise noted. When described on 8/11/82 the soil profile was dry throughout.)

A--0 to 13 cm; dark grayish brown (10YR 4/2) silt loam, black (10YR 2/1) moist; moderate medium platy structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine tubular pores; 5 percent gravel; slightly acid (pH 6.1); clear smooth boundary. (10 to 30 cm thick)

Bt1--13 to 30 cm; grayish brown (10YR 5/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; strong fine angular blocky structure; hard, friable, moderately sticky and moderately plastic; many very fine and fine roots; many very fine tubular pores; common distinct clay films on faces of peds and in pores; slightly acid (pH 6.5); clear wavy boundary. (13 to 25 cm thick)

Bt2--30 to 53 cm; brown (10YR 5/3) clay, dark brown (10YR 3/3) moist; moderate medium prismatic structure; very hard, very firm, very sticky and very plastic; common very fine roots; common very fine tubular pores; many distinct clay films on faces of peds and in pores; 5 percent gravel, 5 percent cobbles; neutral (pH 6.7); gradual wavy boundary. (13 to 38 cm thick)

Bt3--53 to 76 cm; pale brown (10YR 6/3) clay, brown (10YR 4/3) moist; strong medium angular blocky structure; very hard, very firm, very sticky and very plastic; common very fine roots; common very fine tubular pores; common distinct clay films on faces of peds and in pores; 5 percent gravel, 5 percent cobbles; neutral (pH 6.9); clear wavy boundary. (13 to 38 cm thick)

Bk--76 to 107 cm; very pale brown (10YR 7/3) gravelly loam, brown (10YR 5/3) moist; massive; hard, firm, slightly sticky and slightly plastic; few very fine roots; few very fine tubular pores; 20 percent gravel; strongly effervescent (35 percent calcium carbonate equivalent); slightly alkaline (pH 7.5); abrupt smooth boundary. (15 to 41 cm thick)

Bkqm--107 to 152 cm; white (10YR 8/1) duripan, light gray (10YR 7/2) moist; platy; indurated; extremely hard, extremely firm; laminar cap 3 mm thick over strongly cemented sand and gravel.

TYPE LOCATION: About 36 miles southwest of Twin Falls, Twin Falls County, Idaho; about 960 feet north and 1,680 feet east of the southwest corner section 29, T. 14 S., R. 13 E.; USGS Cedar Creek Reservoir 7.5 minute topographic quadrangle; latitude 42 degrees 10 minutes 29 seconds N and longitude 114 degrees 57 minutes 46 seconds W; WGS84 Decimal Degrees 42.1747222 latitude, -114.9627778 longitude.

RANGE IN CHARACTERISTICS:
Depth to bedrock - more than 152 cm.
Depth to duripan - 100 to 152 cm.
Thickness of mollic epipedon - 50 to 66 cm.
Base saturation - 65 to 75 percent in theupper 75 cm.
Average annual soil temperature - 6.7 to 7.8 degrees C.
Soil Moisture: This soil is usually moist, but is dry for 45 to 70 consecutive days during the late summer and autumn. Typic xeric moisture regime.

A horizon
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 1 or 2 dry or moist

Bt horizons
Value - 4 through 6 dry, 2 through 4 moist
Chroma - 2 or 3 dry or moist
Texture - silty clay loam or clay
Clay content -30 to 55 percent (average 35 to 50 percent upper 50 cm).
Cobbles - 0 to 5 percent
Gravel - 0 to 5 percent

Bk horizon
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 3 or 4 dry or moist
Texture - GR-L, GR-CL, or GRV-L
Gravel content - 20 to 35 percent
Clay content - 20 to 35 percent

Bkqm horizon
Thickness of first silica lamination - 3 to 25 mm.
Thickness of duripan - 50 or more cm

COMPETING SERIES: These are the Crowcamp and Siroco. Crowcamp soils are somewhat poorly drained and have base saturation in excess of 75 percent in the upper 75 cm. Siroco soils have more than 75 percent base saturation in the upper 75 cm, have more than 15 percent rock fragments in the upper 50 cm of the argillic horizon, and receive 380 to 460 mm of precipitation.

GEOGRAPHIC SETTING: Iwica soils are on terraces. The slope ranges from 2 to 6 percent. The soils formed in alluvium from mixed sources. Elevations are 1,680 to 1,830 meters. The average annual precipitation ranges from 300 to 380 mm, and the average annual temperature is 5.6 to 6.7 degrees C. The frost-free period is 90 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Budlewis, Chayson, Howcree, Mug, and Tanner soils. Budlewis soils occur on the same landscape and are moderately deep to a hardpan. Chayson, Howcree, Mug, and Tanner soils occur on lower terraces. Chayson and Tanner are moderately deep to a duripan. Howcree soils are very deep and clayey-skeletal. Mug soils are moderately deep to welded tuff.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; slow runoff; slow saturated hydraulic conductivity.

USE AND VEGETATION: Iwica soils are used for rangeland. Native vegetation is Idaho fescue and mountain big sagebrush.

DISTRIBUTION AND EXTENT: Iwica soils are of small extent in south central Idaho. MLRA 25.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California

SERIES ESTABLISHED: Twin Falls County, Idaho, 1992.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 53 cm (A, Btl and Bt2 horizons).
Argillic horizon - The zone from 13 to 76 cm (Bt1, Bt2 and Bt3 horizons).
Calcic horizon - The zone from 76 to 107 cm (Bk horizon.)
Duripan - The zone from 107 to 152 cm (Bqkm horizon).

Control section - 13 to 63 cm (Bt1, Bt2 and part of Bt3 horizons).

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National Cooperative Soil Survey
U.S.A.