LOCATION MALPAIS NV

Established Series
Rev. JBF
09/2019

MALPAIS SERIES

The Malpais series consists of very deep, well drained soils that formed in alluvium and colluvium derived from mixed rocks. Malpais soils are on fan piedmonts, alluvial fans and colluvial slopes bordering mountains. Slopes are 2 to 15 percent. The mean annual precipitation is about 175 mm and the mean annual temperature is about 10 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Typic Haplocambids

TYPICAL PEDON: Malpais gravelly loamy sand--rangeland. (Colors are for dry soil unless otherwise noted.) The surface is covered with about 40 percent gravel, 10 percent cobbles and 5 percent stones.

A--0 to 8 cm; light brownish gray (10YR 6/2) gravelly loamy sand, very dark grayish brown (10YR 3/2), moist; weak thin platy structure; soft, very friable, nonsticky and nonplastic; few very fine roots; few fine and many very fine interstitial pores; 10 percent cobbles and 15 percent gravel; slightly alkaline (pH 7.8); abrupt smooth boundary. (8 to 15 cm thick)

Bw1--8 to 30 cm; brown (10YR 5/3) cobbly sandy loam, dark brown (10YR 3/3), moist; weak fine subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; common very fine roots; few fine and many very fine interstitial pores; 15 percent cobbles and 15 percent gravel; moderately alkaline (pH 8.2); clear wavy boundary. (0 to 30 cm thick)

Bw2--30 to 64 cm; brown (10YR 5/3) very cobbly sandy loam, dark brown (10YR 3/3), moist; weak fine subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; few fine and medium roots, common very fine roots; few fine and many very fine interstitial and tubular pores; 30 percent cobbles and 20 percent gravel; moderately alkaline (pH 8.2); clear wavy boundary. (10 to 50 cm thick)

Bk1--64 to 112 cm; pale brown (10YR 6/3) extremely cobbly sandy loam, dark brown (10YR 3/3), moist; massive; slightly hard, very friable, nonsticky and nonplastic; few very fine roots; many very fine interstitial pores; 30 percent cobbles and 40 percent gravel; moderately alkaline (pH 8.4); clear wavy boundary. (25 to 60 cm thick)

Bk2--112 to 152 cm; grayish brown (10YR 5/2) very cobbly sandy loam, dark brown (10YR 3/3), moist; massive; slightly hard, very friable, nonsticky, nonplastic; few very fine roots; many very fine interstitial pores; 15 percent cobbles and 20 percent gravel; moderately alkaline (pH 8.4);.

TYPE LOCATION: Lyon County, Nevada; about 2,460 feet south of the northwest corner of section 16, T. 12 N., R. 25 E.; USGS Yerington, NV 7.5 minute topographic quadrangle; latitude 38 degrees 54 minutes 14 seconds N and longitude 119 degrees 12 minutes 1 second W; WGS84 Decimal Degrees 38.9038889 latitude, -119.200278 longitude.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually dry, moist in some part for short periods from mid-October to mid-May; typic aridic soil moisture regime.
Mean annual soil temperature: 10 to 12 degrees C.
Depth to base of the Bw horizon: 38 to 90 cm.
Depth to segregated carbonates: 30 to 80 cm.

Particle-size control section - Clay content: 10 to 18 percent.
Rock fragments: 50 to 70 percent.

A horizon
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 or 3.
Reaction: Neutral through moderately alkaline.
Effervescence: Typically noneffervescent, but is slightly effervescent in some pedons subject to recharge from dust.
Other features: Dry Value of 5 is only in the surface 3 to 5 cm.

Bw horizons
Value: 5 or 6 dry, 3 through 5 moist.
Chroma: 2 or 3.
Structure: Weak to moderate, thin platy or medium or coarse prismatic or subangular blocky or it is massive.
Consistence: Soft to hard dry and very friable or friable moist, nonsticky or slightly sticky and nonplastic or slightly plastic wet.
Texture: Loam or sandy loam.
Texture modifiers: Very gravelly, cobbly or very cobbly.
Reaction: Neutral through moderately alkaline.
Effervescence: Noneffervescent or slightly effervescent; pedons with thin lime coats on undersides of rock fragments have a noneffervescent matrix.
Other features: Values of 5 dry and 3 moist reflect lithochromic colors.

Bk horizons
Hue: 10YR or 2.5Y.
Value: 5 through 7 dry, 3 through 5 moist.
Chroma: 2 through 4.
Texture: Loam or sandy loam.
Texture modifiers: Extremely cobbly or very cobbly.
Reaction: Moderately alkaline or strongly alkaline.
Secondary lime: Few to many lime coated rock fragments and soft seams and filaments of lime.
Other features: Values of 5 dry and 3 moist reflect lithochromic colors.

COMPETING SERIES: This is the Hollywell and Whirlo series.

Hollywell soils are intermittently moist for 10 to 20 days cumulative during July through September. Whirlo soils have a Bw horizon with less than 30 percent rock fragments.

GEOGRAPHIC SETTING: Malpais soils are on alluvial fans and colluvial slopes bordering hills and mountain fronts. These soils formed in alluvium and colluvium derived from mixed rocks, mainly basalt, rhyolite and andesite with a small component of loess high in volcanic ash. Slopes are 2 to 15 percent. Elevations are 1,340 to 1,890 meters. The climate is cool, semiarid with hot, dry summers and cool, moist winters. The mean annual precipitation is 125 to 200 mm, mean annual temperature is 9 to 11 degrees C, and the frost-free season is 100 to 130 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are Perazzo, Rawe and Yerington soils. Perazzo soils have an argillic horizon with 20 to 30 percent clay. Rawe soils have an argillic horizon with 40 to 50 percent clay. Yerington soils have a sandy particle-size control section.

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

USE AND VEGETATION: Rangeland and wildlife habitat. The vegetation is principally Nevada ephedra, Bailey greasewood, fourwing saltbrush, Nevada dalea and Indian ricegrass.

DISTRIBUTION AND EXTENT: Western, northern and central Nevada. The soils are of small extent. MLRA 26, 27.

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

SERIES ESTABLISHED: Nye County (Big Smoky Valley Area), Nevada, 1972.

REMARKS: Diagnostic horizons and features recognized in the pedon are:
Ochric epipedon - The zone from the soil surface to 18 cm (A and part of Bw1 horizon).
Cambic horizon - The zone from 8 to 64 cm (Bw1 and Bw2 horizon).
Particle-size control section - The zone from 25 to 100 cm (Bw2 and portions of the Bw1 and Bk horizons).

ADDITIONAL DATA: The type location was moved to Lyon County in 05/2009 to better reflect the concept of the series. The Malpais concept in the Tuscarora Area and Big Smoky Valley area should be checked during updates. The Malpais concept in the Tuscarora area might fit with the concept of the Wiften series.

National Cooperative Soil Survey
U.S.A.