LOCATION MOTOQUA UT+NM NV WYEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Aridic Lithic Argiustolls
TYPICAL PEDON: Motoqua very gravelly sandy loam--rangeland. (Colors are for dry soil unless otherwise noted.) The soil surface has just under 80 percent cover with a gravel pavement.
A--0 to 2 inches; brown (7.5YR 4/2) very gravelly sandy loam, very dark brown (7.5YR 2/2) moist; weak medium platy structure parting to moderate very fine and fine granular; soft, friable, nonsticky and nonplastic; few very fine roots; many fine and very fine interstitial pores; 55 percent gravel; slightly acid (pH 6.4); clear smooth boundary. (2 to 10 inches thick)
BA--2 to 8 inches; brown (7.5YR 4/2) very gravelly loam, dark brown (7.5YR 3/2) moist; weak medium subangular blocky structure parting to moderate very fine and fine granular; soft, friable, slightly sticky and slightly plastic; few fine and common very fine roots; many very fine interstitial pores; 40 percent rock fragments; neutral (pH 6.6); clear smooth boundary. (0 to 8 inches thick)
Bt1--8 to 12 inches; brown (7.5YR 4/2) very gravelly sandy clay loam, dark brown (7.5YR 3/2) moist; weak medium prismatic structure parting to moderate fine subangular blocky; hard, firm, moderately sticky and moderately plastic; few medium, fine, and very fine roots; few fine and common very fine interstitial and tubular pores; 55 percent rock fragments; neutral (pH 6.8); clear smooth boundary. (4 to 10 inches thick)
Bt2--12 to 16 inches; brown (7.5YR 5/3) very gravelly sandy clay loam, brown (7.5YR 4/3) moist; weak medium prismatic structure parting to moderate fine subangular blocky; hard, firm, moderately sticky and moderately plastic; few fine and very fine roots; common very fine tubular and interstitial pores; 55 percent rock fragments; slightly acid (pH 6.4); clear wavy boundary. (0 to 5 inches thick)
R--16 inches; fractured volcanic rock.
TYPE LOCATION: Washington County, Utah; east of Beaver Dam Wash on Middle Ridge about 0.5 mile southwest of the Middle Ridge exclosure; approximately 1,320 feet east and 1,585 feet north of the southwest corner of section 32, T. 38 S., R. 19 W.; USGS Docs Pass 7.5 minute topographic quadrangle; 37 degrees 26 minutes 08 seconds north latitude and 114 degrees 0 minutes 24 seconds west longitude, NAD83.
RANGE IN CHARACTERISTICS:
Soil moisture - The soil moisture regime is ustic bordering on aridic. The type location is in an area that is transitional between the xeric and ustic moisture regimes.
Mean annual soil temperature - 47 to 57 degrees F.
Mean summer soil temperature - 65 to 70 degrees F.
Mollic epipedon thickness - 7 to 17 inches; includes the Bt1 horizon.
Depth to bedrock - 8 to 20 inches to a lithic contact.
Reaction - Slightly acid through slightly alkaline.
A horizon
Hue: 5YR through 10YR.
Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3, dry or moist.
Texture: Gravelly loam, very stony loam, very gravelly sandy loam, very cobbly sandy loam, very gravelly sandy clay loam, very cobbly sandy clay loam, or extremely cobbly loam.
Rock fragments: 15 to 95 percent gravel and cobbles.
Bt horizons
Hue: 5YR through 10YR.
Value: 3 through 6 dry, 3 or 4 moist.
Chroma: 2 through 4, dry or moist.
Texture: Very gravelly loam, very cobbly loam, very gravelly sandy clay loam, very cobbly sandy clay loam, very gravelly clay loam, or very cobbly clay loam. Clay content: 20 to 35 percent.
Rock fragments: 35 to 80 percent.
Structure: Weak to strong, medium or coarse prismatic structure that parts to moderate or strong, very fine through medium subangular blocky or angular blocky structure.
C horizon (where present)
Hue: 7.5YR or 10YR.
Value: 5 through 7 dry, 4 or 5 moist.
Chroma: 3 or 4, dry or moist.
Texture: Gravelly sandy loam, very gravelly sandy loam, or extremely gravelly sandy loam.
Rock fragments: 20 to 80 percent.
COMPETING SERIES: These are the Buckspring, Montvale, Santa Fe, and Slidymtn series.
Buckspring soils have identifiable secondary carbonates in the argillic horizon, are dominated by rock fragments of limestone, and have an aridic moisture regime that borders on ustic. Montvale soils have horizons with identifiable secondary carbonates. Santa Fe soils are dominated by rock fragments of granite and have a mollic epipedon that extends to the bedrock contact. Slidymtn soils have an aridic moisture regime that borders on ustic.
GEOGRAPHIC SETTING: Motoqua soils are on mountain slopes. These soils formed in residuum and colluvium derived from volcanic rocks such as andesite, rhyolite, and tuff. Slopes are 2 to 70 percent. Elevations range from 4,000 to 8,500 feet. The mean annual precipitation is 12 to 14 inches, the mean annual air temperature is 45 to 55 degrees F., the mean summer temperature is 72 to 76 degrees F., and the frost-free period is 90 to 180 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Nehar, Quazo, Tortugas, and Welring soils. Nehar soils have ochric epipedons and are more than 40 inches deep to bedrock. Quazo and Welring soils have ochric epipedons. Tortugas soils do not have argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; very high surface runoff; moderate permeability (moderately high or high saturated hydraulic conductivity).
USE AND VEGETATION: Motoqua soils are used for rangeland and woodland. The vegetation in the type location area is Wyoming big sagebrush, Utah serviceberry, Stansbury cliffrose, shrub live oak, singleleaf pinyon, Utah juniper, Haplopappus sp., buckbrush, desert bitterbrush, desert almond, muttongrass, bottlebrush squirreltail, and galleta.
DISTRIBUTION AND EXTENT: Southwestern Utah, southeastern Nevada, western New Mexico, and western Wyoming. These soils are extensive with about 193,000 acres of the series mapped to date. The original series concept, type location, and nearly 40 percent of the mapped acreage is in MLRA 29. Other mapped acreage occurs in MLRAs 35 and 36 in New Mexico and MLRA 67 in Wyoming. The soils in New Mexico and Wyoming need to be correlated to other series that better represent their properties and moisture patterns.
MLRA OFFICE RESPONSIBLE: Reno, Nevada.
SERIES ESTABLISHED: Washington County, Utah, 1972.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 12 inches (A, BA, and Bt1 horizons).
Argillic horizon - The zone from 8 to 16 inches (Bt1 and Bt2 horizons).
Lithic contact - The boundary at 16 inches to underlying hard, unweathered bedrock (R layer).
Particle-size control section - The zone from 8 to 16 inches (Bt1 and Bt2 horizons).
The revision of December 2006 updated the taxonomic class from the subgroup of Lithic Argiustolls due to the soil having an ustic moisture regime that borders on aridic.