LOCATION DUCO NV+CA ID

Established Series
Rev. PWB-RLB-JVC-JBF
05/2016

DUCO SERIES

The Duco series consists of shallow, well drained soils that formed in colluvium and residuum derived dominantly from volcanic rocks. Duco soils are on structural benches, hills, and mountains. Slopes are 4 to 75 percent. The mean annual precipitation is about 300 mm and the mean annual temperature is about 9 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Aridic Lithic Argixerolls

TYPICAL PEDON: Duco very stony loam--forest land. (Colors are for dry soil unless otherwise noted.)

A1--0 to 5 cm; grayish brown (10YR 5/2) very stony loam, very dark brown (10YR 2/2) moist; weak medium granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine roots; common very fine vesicular and few fine tubular pores; 45 percent stones; neutral (pH 6.6); abrupt smooth boundary. (3 to 8 cm thick)

A2--5 to 13 cm; dark grayish brown (10YR 4/2) gravelly loam, very dark brown (10YR 2/2) moist; moderate medium granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine, fine and few medium and coarse roots; many very fine tubular pores; 20 percent gravel and 5 percent stones; neutral (pH 6.8); abrupt wavy boundary. (0 to 10 cm thick)

Bt1--13 to 25 cm; dark grayish brown (10YR 4/2) gravelly loam, very dark brown (10YR 2/2) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; many very fine and fine, and few medium roots; common very fine tubular pores; few faint clay films coating and bridging sand grains; 20 percent gravel; neutral (pH 6.8); abrupt wavy boundary. (3 to 20 cm thick)

Bt2--25 to 48 cm; brown (10YR 5/3) very gravelly clay loam, dark brown (10YR 3/3) moist; moderate fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine, fine and medium roots; many very fine tubular pores; many distinct clay films on faces of peds; 40 percent gravel and 10 percent cobbles; neutral (pH 6.8); abrupt wavy boundary. (0 to 28 cm thick)

R--48 cm; hard fractured andesite; common distinct clay films lining fracture planes; few fine roots in fractures.

TYPE LOCATION: Douglas County, Nevada; about 9 miles southeast of Gardnerville on a northeast-facing slope in the hills west of Carters Station; approximately 1,000 feet west and 1,600 feet north of the southeast corner of section 7, T. 11 N., R. 21 E.; USGS Carters Station 7.5 minute topographic quadrangle; latitude 38 degrees 49 minutes 46 seconds N and longitude 119 degrees 39 minutes 50 seconds W; UTM Zone 11, 268755e, 4301099n; WGS84 Decimal Degrees 38.8284444 latitude, -119.663889 longitude.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually moist in winter and spring, dry in summer through late fall; aridic moisture regime that borders on xeric.
Mean annual soil temperature: 8 to 12 degrees C.
Mollic epipedon thickness: 18 to 50 cm; commonly includes the Bt1 horizon.
Depth to base of argillic horizon: 25 to 38 cm.
Depth to bedrock: 25 to 50 cm to a lithic contact.
Reaction: Slightly acid through slightly alkaline.
Other features: Some pedons have only one Bt horizon constituting the argillic horizon.

Particle-size control section - Clay content: averages 27 to 35 percent.
Rock fragments: Average 35 to 80 percent, with 20 to 70 percent pebbles, 0 to 20 percent cobbles, and 0 to 40 percent stones. Stones are usually in the Bt2 horizon. Lithology of fragments are volcanic rocks such as andesite or rhyolite.

A horizons
Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 1 through 3, dry or moist.
Organic matter content: 1 to 3 percent.

Bt1 horizon
Hue: 10YR or 7.5YR.
Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3, dry or moist.
Fine-earth texture: Loam, sandy clay loam, or clay loam.
Rock fragments: 20 to 80 percent, mainly gravel. Some pedons are dominated by stones.
Structure: Subangular blocky or angular blocky.
Consistence: Slightly hard or hard, slightly sticky or moderately sticky, slightly plastic or moderately plastic.
Organic matter content: 1 or 2 percent.

Bt2 horizon
Hue: 10YR or 7.5YR.
Value: 4 through 6 dry, 2 through 4 moist.
Chroma: 2 through 4, dry or moist.
Structure: Moderate or strong, fine or medium, subangular or angular blocky.

COMPETING SERIES: These are the Argabak, Bellehelen, Brier, Horseflat, Nuhelen, Ocud, Orhood, Reywat, and Upatad series.

Argabak soils have mollic epipedons that are 13 to 18 cm thick. Bellehelen, Brier and Nuhelen soils are intermittently moist in some part for 10 to 20 days cumulative between July and October. Horseflat soils do not have fractured bedrock with illuvial clay, have secondary silica coats over 30 percent of the surface area of the bedrock, have transitional AB horizons, and have more than 35 percent rock fragments in the upper part of the argillic horizon. Ocud soils average 15 to 25 percent clay in the particle-size control section. Orhood soils average 18 to 27 percent clay in the particle-size control section and are dominated by cobbles. Reywat soils have identifiable secondary carbonates in the lower part of the Bt2 horizon, on the surface of the lithic contact, or in cracks within the bedrock. Upatad soils have 5 to 15 percent durinodes and identifiable secondary carbonates in the particle-size control section.

GEOGRAPHIC SETTING: Duco soils are on structural benches, hills, and mountains. These soils formed in colluvium and residuum derived dominantly from volcanic rocks such as rhyolite and andesite, but also from welded tuff, basalt, metasedimentary, and some metavolcanic rocks. Slopes are 4 to 75 percent. Elevations range from 1,220 to 2,445 meters in Nevada and California and as low as 807 meters in Idaho. The climate is semiarid with cool, moist winters and warm, dry summers. The mean annual precipitation is 250 to 400 mm and the mean annual temperature is 6 to 11 degrees C. The frost-free period is typically 70 to 115 days, but ranges to 155 days in Idaho.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cagle, Deven, and Nosrac soils. Cagle soils are fine, moderately deep to paralithic contacts, and occur on adjacent south and west-facing slopes. Deven soils are clayey. Nosrac soils are very deep.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; very high surface runoff; moderately high saturated hydraulic conductivity.

USE AND VEGETATION: Duco soils are used for forest land, livestock grazing, and wildlife habitat. The vegetation is mainly a forest canopy of singleleaf pinyon and Utah juniper with an understory of Wyoming big sagebrush, antelope bitterbrush, Currant ssp., Thurber's needlegrass, bluebunch wheatgrass, Sandberg's bluegrass, and bottlebrush squirreltail. Duco soils in Idaho do not have a forested plant community. This pedon is correlated to F026XY044NV, PIMO-ARTRV woodland.

DISTRIBUTION AND EXTENT: Western Nevada, northeastern California, and southwestern Idaho. These soils are moderately extensive. The series concept and main acreage is in MLRA 26 in Nevada and California. Other acreage occurs in MLRAs 27 and 28B in Nevada and MLRA 10 in Idaho.

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

SERIES ESTABLISHED: Washoe County (South Part), Nevada, 1980.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 48 cm (A1, A2, Bt1, and Bt2 horizons).
Argillic horizon - The zone from 13 to 48 cm (Bt1 and Bt2 horizons).
Lithic contact - The boundary at 48 cm to underlying hard bedrock (R layer).
Particle-size control section - The zone from 13 to 48 cm (Bt1 and Bt2 horizons).

Classification was updated to 11th edition on 07/2011 and changed from Lithic Argixerolls to Aridic Lithic Argixerolls.

This series is mapped in pinyon-juniper woodland in Nevada and California and in rangeland in Idaho. There is a need to split the series to better account for these wide differences in plant community and soil climate. The series concept needs to be evaluated and clarified as a part of the MLRA update process.

ADDITIONAL DATA: User pedon ID: 2006NV005004.

National Cooperative Soil Survey
U.S.A.