LOCATION SIERRAVISTA AZEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Petronodic Calciargids
TYPICAL PEDON: Sierravista fine sandy loam-rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 3 inches; yellowish red (5YR 4/6) fine sandy loam, dark reddish brown (5YR 3/4) moist; weak thin platy structure; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; common fine irregular pores; noneffervescent; slightly alkaline (pH 7.4); abrupt smooth boundary. (1 to 5 inches thick)
Bt--3 to 21 inches; dark red (2.5YR 3/6) very gravelly sandy clay loam, dark reddish brown (2.5YR 3/4) moist; weak fine subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; few fine tubular pores; many distinct clay films on sand and gravel, and between sand grains; 40 percent gravel, 10 percent petronodes, and 5 percent cobble; noneffervescent; slightly alkaline (pH 7.6); clear smooth boundary. (10 to 18 inches thick)
Btc--21 to 42 inches; red (2.5YR 4/6) very gravelly sandy clay loam, dark red (2.5YR 3/6) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine roots; few fine tubular pores; many distinct clay films on sand, gravel, and between sand grains; 30 percent gravel, 20 percent petronodes; noneffervescent; slightly alkaline (pH 7.8); abrupt wavy boundary (15 to 25 inches thick)
Bkc--42 to 60 inches; 80 percent pink (5YR 8/3) and 20 percent weak red (2.5YR 4/2) extremely gravelly sandy loam, yellowish red (5YR 5/6) moist; massive; extremely hard, friable, nonsticky and nonplastic, weakly cemented by calcium carbonate; few fine roots in cracks; many distinct calcium carbonate coatings on rock fragments; 40 percent gravel, 40 percent petronodes and 5 percent cobble; violently effervescent; moderately alkaline (pH 8.2).
TYPE LOCATION: Cochise County, Arizona; located at a latitude of 31 degrees, 37 minutes, 30 seconds North and longitude of 110 degrees, 18 minutes, 30 seconds West.
RANGE IN CHARACTERISTICS:
Soil moisture - Intermittently moist in some part of the soil moisture control section during July - September and December - February. Driest during May and June. Ustic aridic soil moisture regime.
Soil temperature: 62 to 69 degrees F.
Rock fragments: more than 35 percent, but can range from 0 to 85 gravel/petronodes percent in any horizon
Petronodic feature: 20 to 50 percent petronodes. Thought to have formed from calcium and magnesium that precipitated out during fluctuating seasonal water tables under a climate much wetter than the present. Repeated wetting and extreme drying of the soil may have been a factor in nodule development. The petronodes have no internal organization and break down completely in HCL acid but not in water.
Reaction: slightly or moderately alkaline
Clay content: 18 to 35 percent in control section
Calcium carbonate equivalent: 0 to 5 percent in the upper horizons and greater than 15 percent in the lower horizons
Depth to calcic horizon: 30 to 50 inches
A horizon
Hue: 7.5YR, 5YR
Value: 3 or 4, dry or moist
Chroma: 4 or 6, dry or moist
Texture: fine sandy loam, sandy loam
Bt and Btc horizons
Hue: 2.5YR, 5YR
Value: 3 through 5, dry or moist
Chroma: 4 or 6, dry or moist
Texture: sandy clay loam, sandy loam
Bkc horizon
Hue: 5YR, 2.5YR
Value: 4, 7 or 8 dry, 3 through 5 moist
Chroma: 2 through 6, dry or moist
Calcium carbonate equivalent: greater than 15 percent with some 3rd and 4th stage cementation
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Sierravista soils are on stream and fan terraces at elevations of 4200 to 4600 feet. Slopes range from 0 to 8 percent. These soils formed in mixed alluvium. The mean annual precipitation is 12 to 16 inches and occurs as thunderstorms during July to September and as gentle rains during December to February. The mean annual air temperature is 60 to 67 degrees F. The frost-free period is 180 to 230 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Gulch, Libby, Bella, Vana, Moco, and Graveyard series. Gulch and Moco soils are fine-loamy. Libby soils are fine. Bella and Vana soils are shallow to a hardpan. Graveyard soils do not have argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately slow permeability.
USE AND VEGETATION: Used for livestock grazing and wildlife habitat. Vegetation includes mesquite, whitethorn, sideoats grama, cane beardgrass, black and blue grama, plains lovegrass, tanglehead, threeawn and false mesquite.
DISTRIBUTION AND EXTENT: Southern Arizona. Sierravista soils are of moderate extent. MLRA is 41.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Cochise County, Arizona. Soil survey of Cochise County, Arizona, Douglas-Tombstone Part; 1996.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 3 inches (A horizon)
Argillic horizon - The zone from 3 to 42 inches (Bt1, Bt2 horizons)
Calcic horizon - The zone from 42 to 60 inches (Bkc horizon)
Soil Taxonomy Second Edition, 1999