LOCATION MAHALA NV+CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Vertic Paleargids
TYPICAL PEDON: Mahala silt loam--rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 4 inches; light gray (10YR 7/2) silt loam, dark grayish brown (10YR 4/2) moist; moderate medium platy structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine and fine vesicular pores; 5 percent fine gravel; neutral (pH 7.2); abrupt smooth boundary. (1 to 4 inches thick)
E--4 to 5 inches; light brownish gray (10YR 6/2) silt loam, dark brown (10YR 3/3) moist; weak medium prismatic structure; hard, friable, moderately sticky and slightly plastic; common very fine, fine and few medium roots; many very fine and few fine tubular pores; light gray (10YR 7/2) uncoated sand grains; common fine distinct dark brown (7.5YR 3/4) masses of iron accumulation; neutral (pH 7.2); abrupt smooth boundary. (0 to 1 inch thick)
2Bt1--5 to 9 inches; brown (10YR 5/3) clay, brown (10YR 4/3) moist; strong medium prismatic structure parting to strong coarse angular blocky, very hard, firm, very sticky and very plastic; common very fine roots; many very fine tubular pores; light gray (10YR 7/2) uncoated sand grains capping prisms; common pressure cutans on faces of peds; slightly alkaline (pH 7.4); clear smooth boundary. (4 to 13 inches thick)
2Bt2--9 to 14 inches; light yellowish brown (10YR 6/4) clay, yellowish brown (10YR 5/4) moist; weak medium prismatic structure parting to moderate coarse angular blocky; very hard, firm, very sticky and very plastic; common very fine roots; many very fine tubular pores; common pressure cutans and common distinct clay films on faces of peds; moderately alkaline (pH 8.0); clear wavy boundary. (5 to 12 inches thick)
2Btk--14 to 26 inches; light yellowish brown (10YR 6/4) clay, yellowish brown (10YR 5/4) moist; moderate medium subangular blocky structure parting to moderate fine subangular blocky; very hard, firm, very sticky and plastic; few very fine roots; many very fine tubular pores; many faint clay films coating sand grains and on faces of peds; slightly effervescent; secondary carbonates finely disseminated in the matrix; moderately alkaline (pH 8.4); clear wavy boundary. (7 to 20 inches thick)
2Cr--26 inches; very pale brown (10YR 7/3) weathered, fractured tuff; few fine discontinuous carbonate coats lining fractures.
TYPE LOCATION: Elko County, Nevada; about 10 miles northwest of Jack Creek; approximately 2,312 feet north and 100 feet west of the southeast corner of section 19, T. 43 N., R. 51 E.; USGS Cornucopia Ridge 7.5 minute topographic quadrangle; 41 degrees 36 minutes 35 seconds north latitude and 116 degrees 16 minutes 50 seconds west longitude, NAD27.
RANGE IN CHARACTERISTICS:
Soil moisture - Usually dry, moist in winter and spring, dry late June through October; Aridic moisture regime that borders on xeric.
Mean annual soil temperature - 47 to 50 degrees F.
Depth to carbonates - 14 to 30 inches.
Depth to bedrock - 20 to 40 inches to a paralithic contact. The paralithic materials below the contact are weathered volcanic rock such as tuff.
Particle-size control section - Clay content: Averages 40 to 60 percent;
Rock fragments: 0 to 20 percent, mainly gravel.
Linear extensibility (LE) - 6 to 9 cm.
Other features - An abrupt horizon boundary is normally present between the E and 2Bt1 horizons accompanied by an abrupt increase in clay content of 15 percent or more.
Reaction - Neutral through moderately alkaline, normally increasing with depth.
A horizon
Value: 5 through 7 dry, 3 or 4 moist.
Chroma: 1 through 3, dry or moist.
Other features: Some pedons have thin AB horizons.
E horizon (when present)
Value: 6 or 7 dry.
Other features: Commonly has uncoated sand grains and common fine distinct masses of iron accumulation.
2Bt horizons
Value: 5 or 6 dry, 4 through 6 moist.
Chroma: 2 through 4 dry, 3 or 4 moist.
Texture: Clay or gravelly clay.
Structure: Weak to strong, medium to coarse prismatic, or columnar weak or moderate fine to coarse subangular or angular blocky or prismatic parting to angular or subangular blocky.
Other features: Uncoated sand grains commonly cap prisms; Pressure cutans are common to many in some part.
Btk horizon
Value: 6 or 7 dry, 5 or 6 moist.
Chroma: 2 through 4, dry or moist.
Texture: Clay or clay loam with gravelly clay loam, or silty clay loam common in some pedons.
Reaction: Slightly alkaline or moderately alkaline.
Identifiable secondary carbonates: Finely disseminated in the matrix but may include threads (filaments) in some pedons.
COMPETING SERIES: These are the Campo, Gooding, Phing, Sorf, Twickenham, and Verdico series.
Campo, Phing, and Twickenham soils are very deep. Gooding soils are deep to duripans. Sorf soils have mean annual soil temperature of 51 to 54 degrees F. Verdico soils do not have albic horizons or 2Btk horizons at a depth of 14 to 30 inches.
GEOGRAPHIC SETTING: Mahala soils are on rock pediments, plateaus, and hills. They typically occur on summit, shoulder, and backslope positions. These soils formed in thin loess mantle over residuum weathered from tuff. Elevations are 5,400 to 6,200 feet. Slopes are 0 to 50 percent. The climate is cool semiarid with warm, dry summers and cool, moist winters. The mean annual precipitation is 10 to 12 inches; mean annual temperature is 45 to 50 degrees F, and the frost- free season is 80 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Alley, Gance, Hunnton, Ramires, and Wieland soils. Alley soils average 20 to 30 percent clay in the argillic horizon. Hunnton soils have indurated duripans between 22 and 35 inches. Ramires soils have mollic epipedons. Gance soils have 35 to 75 percent rock fragments in the particle-size control section. Wieland soils do not have an abrupt textural change between the ochric epipedon and the argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; medium to very high surface runoff; very slow permeability (low or moderately low saturated hydraulic conductivity).
USE AND VEGETATION: Mahala soils are used for rangeland and wildlife habitat. The vegetation is mainly low sagebrush, Douglas rabbitbrush, Thurber's needlegrass, and Sandberg's bluegrass.
DISTRIBUTION AND EXTENT: Northern Nevada and northeastern California. These soils are not extensive with about 9,000 acres of the series mapped to date. The series concept and main acreage is in MLRA 25, while other acreage occurs in MLRA 23.
MLRA OFFICE RESPONSIBLE: Reno, Nevada.
SERIES ESTABLISHED: Elko County, Nevada (Central Part), 1986.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 5 inches (A and E horizon).
Albic horizon - The zone from 4 to 5 inches (E horizon).
Paleargids great group feature and abrupt textural change - The abrupt clay increase of more than 20 percent at 5 inches (between the E and 2Bt1 horizons).
Argillic horizon - The zone from 5 to 26 inches (2Bt1, 2Bt2, and 2Btk horizons).
Paralithic contact - The boundary at 26 inches to underlying weathered bedrock (2Cr layer).
Particle-size control section - The zone from 5 to 25 inches (2Bt1 and 2Bt2 horizons and part of the 2Btk horizon).