LOCATION ORWASH                  NV+AZ

Established Series
Rev. DPC/JBF/WED/ET
12/2015

ORWASH SERIES

The Orwash series consists of very deep, somewhat excessively drained soils that formed from mixed alluvium derived from granitic sources. Orwash soils are on fan aprons, fan skirts, and alluvial flats. Slope ranges from 0 to 15 percent. Mean annual precipitation is about 6 inches and mean annual temperature is about 59 degrees F.

TAXONOMIC CLASS: Sandy, mixed, thermic Typic Torriorthents

TYPICAL PEDON: Orwash gravelly fine sandy loam, rangeland. (Colors are for dry soil unless otherwise noted.) The soil surface is covered by approximately 40 percent pebbles and 5 percent cobbles.

A1--0 to 3 inches; pale brown (10YR 6/3) gravelly fine sandy loam, brown (10YR 4/3) moist; weak medium platy structure; soft, very friable, nonsticky and nonplastic; few very fine roots; common very fine and fine vesicular pores; 25 percent pebbles; slightly effervescent; moderately alkaline (pH 8.2); clear smooth boundary. (1 to 4 inches thick)

A2--3 to 8 inches; pale brown (10YR 6/3) gravelly loamy coarse sand, brown (10YR 4/3) moist; weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; few very fine and fine roots; few very fine and fine vesicular and interstitial pores; 20 percent pebbles, 5 percent cobbles; violently effervescent; moderately alkaline (pH 8.4); clear smooth boundary. (0 to 7 inches thick)

C1--8 to 18 inches; very pale brown (10YR 7/3) gravelly loamy coarse sand, brown (10YR 4/3) moist; massive; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; many very fine and fine interstitial pores; 20 percent pebbles; violently effervescent; moderately alkaline (pH 8.4); clear wavy boundary.

C2--18 to 29 inches; very pale brown (10YR 7/3) very gravelly loamy coarse sand, brown (10YR 4/3) moist; massive; soft, very friable, nonsticky and nonplastic; few very fine and fine roots; many very fine and fine interstitial pores; 40 percent pebbles; slightly effervescent; moderately alkaline (pH 8.4); clear wavy boundary.

C3--29 to 61 inches; very pale brown (10YR 7/3) gravelly loamy coarse sand, brown (10YR 4/3) moist; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; many very fine and fine interstitial pores; 30 percent pebbles; strongly effervescent; moderately alkaline (pH 8.4). (Combined thickness of the C horizons is 40 to 60 inches.)

TYPE LOCATION: Esmeralda County, Nevada; about 2,400 feet north and 2,000 feet east of the apparent southwest corner of section 32, T. 8 S., R. 43 E.

RANGE IN CHARACTERISTICS:

Soil moisture - Usually dry, but moist in some parts for short periods during winter and early spring months, and for 10 to 20 days cumulative between July to October due to convection storms.

Soil temperature - 59 to 63 degrees F.

Reaction - Moderately alkaline or strongly alkaline.

Effervescence - Slightly effervescent to violently effervescent. A horizons are noneffervescent in some pedons.

Control section - Rock fragments: Averages 15 to 35 percent gravel, which are dominantly fine gravel.

A horizon - Value: 6 or 7 dry, 4 or 5 moist.
Chroma: 2 through 4.

C horizon - Value: 6 or 7 dry, 4 through 6 moist.
Chroma: 2 through 4.
Texture: Dominantly loamy coarse sand or loamy sand with thin subhorizons of coarse sandy loam or coarse sand in some pedons.
Rock fragments: Average 15 to 35 percent, but most pedons contain subhorizons with 35 to 60 percent rock fragments.

COMPETING SERIES: These are the Amole (AZ), Challenger (CA), Hypoint (NV), Livefire (CA), Redington (AZ), Shortbread (AZ) and Yellowrock (CA) series. Amole soils lack a subhorizon with more than 35 percent rock fragments in the control section, are noncalcareous in the upper part of the control section and have soil temperatures of 66 to 72 degrees F. Challenger soils have loamy texures and SARs of 30 to 100 at depths starting below 30 to 40 inches. Hypoint soils have soil temperatures of 64 to 71 degrees F. and are not dominated by fine gravel. Livefire soils have soil temperatures of 63 to 71 degrees F. and are not dominated by fine gravel. Redington soils contain densic (Cd) horizons. Shortbread soils have 0 to 15 percent rock fragments in the particle-size control section. Yellowrock soils do not have 10 to 20 days summer precipitation, not dominated by fine gravel, and have soil temperature of 66 to 70 degrees F.

GEOGRAPHIC SETTING: Orwash soils are on fan aprons, fan skirts, and alluvial flats. These soils formed in mixed alluvium with a granitic influence or alluvium from rhyolites that weather to fine sized pebbles. Elevations are 3,000 to 4,600 feet. Slope ranges from 0 to 15 percent. The climate is warm and arid, with hot, dry summers and cool winters. The mean annual air temperature is 57 to 61 degrees F.; the average annual precipitation is 4 to 8 inches, and the frost free season is 150 to 240 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arizo and Lanip soils. Arizo soils are sandy-skeletal. Lanip soils have an argillic horizon and fine-loamy particle-size control section.

DRAINAGE AND PERMEABILITY: Somewhat excessively drained; low runoff; rapid permeability.

USE AND VEGETATION: These soils are used for rangeland and wildlife habitat. The present vegetation is mainly creosotebush, white bursage and shadscale.

DISTRIBUTION AND EXTENT: Southern Nevada. MLRA 30. These soils are not extensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: PHOENIX, ARIZONA

SERIES ESTABLISHED: Esmeralda County, Nevada, 1984.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon - 0 to 7 inches. (A1 and part of the A2 horizon)

Particle-size control section - 10 to 40 inches. (C2 and parts of the C1 and C3 horizons)

Responsibility for this series was transferred from Davis to Phoenix 12/2015. The last revision to the series was 6/2006. ET

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National Cooperative Soil Survey
U.S.A.