LOCATION STEWVAL NVEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Lithic Xeric Haplargids
TYPICAL PEDON: Stewval very gravelly fine sandy loam--rangeland. (Colors are for dry soil unless otherwise noted.) The soil surface is covered with approximately 55 percent gravel.
A--0 to 3 cm; brown (10YR 5/3) very gravelly fine sandy loam, dark brown (10YR 3/3) moist; moderate medium platy structure; slightly hard, very friable, slightly sticky and slightly plastic; few very fine roots; common very fine vesicular and many very fine and fine interstitial pores; 45 percent gravel; slightly effervescent; slightly alkaline (pH 7.7); abrupt smooth boundary. (3 to 13 cm thick)
Bt--3 to 10 cm; brown (7.5YR 5/4) extremely gravelly loam, brown (7.5YR 4/4) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and common fine roots; many very fine interstitial pores; few faint clay films lining pores; 70 percent gravel; strongly effervescent; slightly alkaline (pH 7.7); abrupt irregular boundary. (8 to 23 cm thick)
R--10 cm; highly fractured, hard rhyolite; few very fine and fine roots in cracks; strongly effervescent; fine discontinuous secondary silica and secondary calcium carbonate masses in cracks; clear wavy boundary.
TYPE LOCATION: Nye County, Nevada; side of a ridge about 1,500 feet south of the highest hill; About 1,370 feet south and 2,375 feet west of the northeast corner, Section 33, T. 11 N., R. 36 E.; latitude 38 degrees 46 minutes 41.7 seconds N, and longitude 117 degrees 56 minutes 2.4 seconds W; NAD83.
RANGE IN CHARACTERISTICS:
Soil moisture - Usually dry; moist in winter and spring months, dry in summer and fall except for 10 to 20 days cumulative between July and October due to convection storms; aridic moisture regime that borders on xeric.
Soil temperature - 11.7 to 15 degrees C.
Depth to bedrock - 10 to 36 cm to a lithic contact.
Reaction - Slightly alkaline or moderately alkaline.
Effervescence - Slightly effervescent to violently effervescent.
Calcium carbonate equivalent - 1 to 5 percent.
Control section - Clay content: Averages 18 to 35 percent.
Rock fragments: 35 to 70 percent gravel, 0 to 10 percent cobbles, 0 to 15 percent stones. Some pedons have 0 to 5 percent flagstones. Lithology of fragments are volcanic rocks such as rhyolite, dacite, andesite, or tuff.
A horizon - Hue: 10YR or 7.5YR.
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 or 3, dry or moist.
Bt horizon - Hue: 10YR through 5YR.
Value: 5 or 6 dry, 3 through 5 moist.
Chroma: 2 through 4, dry or moist.
Texture (less than 2 mm fraction): Loam or clay loam.
Structure: Weak or moderate fine or medium subangular blocky or granular.
Consistence: Soft or slightly hard, very friable to friable moist, slightly plastic or moderately plastic.
Clay films: Few to common.
Other features: Secondary silica and carbonate pendants are on undersides of rock fragments in some pedons.
COMPETING SERIES:
Atlow (NV) - have bedrock at 36 to 50 cm
Broomstick (NV) - have bedrock at 36 to 50 cm
Checkett (UT)- have bedrock at 36 to 50 cm
Cottle (ID) - not intermittently moist in some part of the moisture control section for 10 to 20 days cumulative between July and October
Fortyday (WA) - have bedrock at 36 to 50 cm
Gabbvally (NV) - do not have carbonates and are noneffervescent in the A and Bt horizons
Hooplite (NV) - not intermittently moist in some part of the moisture control section for 10 to 20 days cumulative between July and October
Nevo (WA) - do not have carbonates and are noneffervescent in the A and Bt horizons
Olac (NV) - not intermittently moist in some part of the moisture control section for 10 to 20 days cumulative between July and October; do not have carbonates and are noneffervescent in the A and Bt horizons
Old Camp (NV) - not intermittently moist in some part of the moisture control section for 10 to 20 days cumulative between July and October
Phliss (NV) - have identifiable secondary carbonates at depths of 8 to 25 cm and are dry from July through October
Sedsked (T NV) - mean annual soil temperature of 8.3 to 11.1 degrees C.
Soughe (NV) - not intermittently moist in some part of the moisture control section for 10 to 20 days cumulative between July and October; do not have carbonates and are noneffervescent in the A and Bt horizons
Thike (NV) - average 12 to 18 percent clay in the particle-size control section
GEOGRAPHIC SETTING: Stewval soils are on hills, mountains, mesas, plateaus, and pediments. They formed in residuum and colluvium derived from volcanic rocks. Slopes are 8 to 75 percent. Elevations range from 1,490 to 2,440 meters. The climate is semiarid with cool, moist winters and warm, dry summers. The mean annual precipitation is 203 to 305 mm, the mean annual temperature is 8.3 to 12.2 degrees C., and the frost-free period is 90 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Annaw, Downeyville, Goldyke soils. Annaw soils are sandy-skeletal, very deep, and have cambic horizons. Downeyville soils are loamy-skeletal, very shallow and shallow to lithic contacts, and have an aridic moisture regime that does not border on xeric. Goldyke soils are loamy, very shallow to paralithic contacts, and do not have diagnostic subsurface horizons.
DRAINAGE AND PERMEABILITY: Well drained; medium to very high runoff; moderate permeability.
USE AND VEGETATION: Stewval soils are used for livestock grazing and wildlife habitat. The present vegetation is mainly black sagebrush, Nevada ephedra, pine bluegrass, bottlebrush squirreltail, and spiny menodora.
DISTRIBUTION AND EXTENT: Western and central Nevada. These soils are extensive, with about 640,000 acres of the series mapped to date. MLRAs 29, 27, and 28B.
MLRA OFFICE RESPONSIBLE: Reno, Nevada.
SERIES ESTABLISHED: Esmeralda County, Nevada, 1984.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: 0 to 3 inch (A horizon).
Argillic horizon: 3 to 10 cm (Bt horizon).
Lithic contact: 10 cm (R layer).
Particle-size control section: 0 to 10 cm (A and Bt horizons).