LOCATION BERNARDINO AZEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Ustic Calciargids
TYPICAL PEDON: Bernardino gravelly clay loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 2 inches; dark brown (7.5YR 3/2) gravelly clay loam, dark brown (7.5YR 3/2) moist; weak medium platy structure parting to moderate fine granular; slightly hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; many very fine irregular pores; 35 percent gravel; slightly alkaline (pH 7.5); abrupt smooth boundary. (1 to 3 inches thick)
Bt1--2 to 9 inches; dark reddish brown (5YR 3/3) gravelly clay loam, dark reddish brown (5YR 3/4) moist; moderate fine subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; few very fine tubular and irregular pores; common faint patchy clay films on faces of peds and lining pores; 20 percent gravel; slightly alkaline (pH 7.5); clear wavy boundary. (5 to 8 inches thick)
Bt2--9 to 15 inches; dark reddish brown (5YR 3/4) gravelly clay, dark reddish brown (5YR 3/4) moist; moderate fine and medium subangular and angular blocky structure; hard, friable, moderately sticky and moderately plastic; few very fine and medium roots; few very fine tubular and common very fine irregular pores; common faint clay films on faces of peds and lining pores; 15 percent gravel; strongly effervescent in spots; moderately alkaline (pH 8.0); clear wavy boundary. (4 to 9 inches thick)
2Bk1--15 to 48 inches; pinkish gray (5YR 7/2) gravelly sandy loam, reddish brown (5YR 5/3) moist; massive; very hard, friable, nonsticky and slightly plastic; few very fine and fine roots; many very fine and fine irregular pores; 30 percent gravel; common fine irregular calcium carbonate masses; violently effervescent; moderately alkaline (pH 8.0); gradual smooth boundary. (30 to 40 inches thick)
2Bk2--48 to 60 inches; pinkish gray (5YR 7/2) very gravelly sandy loam, reddish brown (5YR 5/3) moist; massive; very hard, friable, nonsticky and slightly plastic; many very fine and fine irregular pores; 40 percent gravel; few fine irregular calcium carbonate masses; strongly effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Santa Cruz County, Arizona; about 2 miles southeast of Sonoita; 500 feet west and 650 feet north of the southeast corner of Section 29, T. 20 S., R. 17 E.
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: 60 to 70 degrees F.
Depth to calcic horizon: 5 to 20 inches. Calcium carbonate equivalent averages 15 to 40 percent and decreases with increasing depth
Rock Fragments: Averages less than 35 percent in the control section; can range to 80 percent in any one horizon
Organic matter: Averages 1 percent or more in the surface
Reaction: Neutral or slightly alkaline in the upper part and slightly or moderately alkaline in the lower part
A horizon
Hue: 5YR, 7.5YR, 10YR
Value: 3 through 6 dry, 2 through 5 moist
Chroma: 2, 3 or 4, dry or moist
Bt horizon
Hue: 2.5YR, 5YR, 7.5YR
Value: 3, 4 or 5 dry, 2, 3 or 4 moist
Chroma: 2 through 6, dry or moist
Texture: Clay loam, clay
Bk or C horizon
Hue: 2.5YR through 10YR
Value: 5 through 8 dry, 4 through 7 moist
Chroma: 2 through 6, dry or moist
Texture: Sandy loam, sandy clay loam, clay loam, loam, loamy sand
COMPETING SERIES: These are the Forrest (AZ), Penthouse (AZ) and Stellar (NM) series. All these soils have a calcic horizon at depths of 20 to 40 inches.
GEOGRAPHIC SETTING: Bernardino soils are on fan terraces and have slopes of 0 to 30 percent. These soils formed in fan alluvium from mixed sources. Elevation ranges from 3500 to 5500 feet. The mean annual precipitation ranges from 12 to 16 inches. The mean annual air temperature is 58 to 68 degrees F. The frost-free period is 160 to 250 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bonita, McAllister, Stronghold, Tombstone and the competing Forrest and White House soils. Bonita soils are fine textured. McAllister soils are fine-loamy. Stronghold and Tombstone soils do not have argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; slow or medium runoff; slow permeability.
USE AND VEGETATION: Bernardino soils are used for livestock grazing and wildlife habitat. The present vegetation is sideoats grama, slender grama, purple grama, plains lovegrass, cane beardgrass, curly mesquite, tobosa, beargrass, and mesquite.
DISTRIBUTION AND EXTENT: Southern Arizona. This series is of moderate extent. MLRA is 41.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Santa Cruz County (Santa Cruz County Area), Arizona; 1971.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 2 inches (A horizon)
Argillic horizon - The zone from 2 to 15 inches (Bt1, Bt2 horizons)
Calcic horizon - The zone from 15 to 60 inches (2Bk1, 2Bk2 horizons)
Soil Taxonomy Second Edition, 1999