LOCATION PIMA AZ+NMEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, calcareous, thermic Typic Torrifluvents
TYPICAL PEDON: Pima silty clay loam--cultivated (colors are for dry soil unless otherwise noted).
Ap--0 to 4 inches; yellowish brown (10YR 5/4) silty clay loam, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure; slightly hard, friable, moderately sticky and slightly plastic; common fine roots; many very fine tubular pores; slightly effervescent; moderately alkaline (pH 8.0); abrupt smooth boundary (4 to 8 inches thick).
A1--4 to 10 inches; brown (10YR 5/3) silty clay loam, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure; slightly hard, friable, moderately sticky and slightly plastic; many fine roots; many fine tubular pores; slightly effervescent; moderately alkaline (pH 8.0); clear smooth boundary (6 to 8 inches thick).
A2--10 to 25 inches; brown (10YR 5/3) silty clay loam, very dark grayish brown (10YR 3/2) moist; massive; slightly hard, friable, moderately sticky and slightly plastic; common fine roots; many fine tubular pores; slightly effervescent; moderately alkaline (pH 8.0); clear smooth boundary (10 to 16 inches thick).
C1--25 to 37 inches; brown (10YR 5/3) silty clay loam, dark brown (10YR 3/3) moist; massive; slightly hard, friable, moderately sticky and slightly plastic; many fine tubular pores; few very fine lime filaments; strongly effervescent; moderately alkaline (pH 8.0).
C2--37 to 60 inches; light yellowish brown (10YR 6/4) silty clay loam, dark yellowish brown (10YR 3/4) moist; massive; slightly hard, friable sticky and slightly plastic; many fine tubular pores; few fine lime filaments; strongly effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Cochise County, Arizona; about 6 miles southwest of Bowie; 3000 feet east and 500 feet north of SW corner section 8, T. 14 S., R. 29 E.
RANGE IN CHARACTERISTICS:
Soil Moisture - Intermittently moist in the soil moisture control section in some part during July to September and December to February. Typic aridic moisture regime.
Rock fragments (particle-size control section) - less than 35 percent gravel.
Thickness of dark epipedon - 20 to more than 40 inches.
A horizon
Hue: 10YR or 7.5YR.
Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3 dry and moist.
Texture: Silt loam, silty clay loam, loam or clay loam. Particle-size control section averages more than 18 percent clay and less than 15 percent sand coarser than very fine sand.
Organic matter: More than 1 percent to more than 20 inches; decreases irregularly or remains high in deep layers.
Reaction: Neutral to moderately alkaline.
Carbonates: Slightly or strongly effervescent.
Stratification: Thin strata of contrasting textures are common.
C horizon
Hue: 10YR or 7.5YR.
Value: 4, 5 or 6 dry, 3, 4 or 5 moist.
Chroma: 2, 3 or 4 dry and moist.
Texture: Silt loam, silty clay loam, loam, clay loam, and fine sandy loam; particle size control section averages more than 18 percent clay and less than 15 percent sand coarser than very fine sand.
Reaction: slightly or moderately alkaline.
Carbonates: Strongly or violently effervescent; lime filaments occur in some pedons.
Stratification: Thin strata of contrasting textures are common.
COMPETING SERIES: These are the Glendale (AZ) and Rift (AZ) series. Glendale soils have less than 1 percent organic matter. Rift soils are moist in the soil moisture control section for less than 20 days cumulative during July-September and occur in the Mohave Desert.
GEOGRAPHIC SETTING: Pima soils are on alluvial fans and flood plains. Elevations range from 1,100 to 5,400 feet. Slopes range from 0 to 3 percent. These soils formed in stratified and mixed alluvium from volcanic, granitic, metamorphic and sedimentary rock. The climate is warm and dry. The average annual precipitation is 6 to 12 inches occurring as summer thunderstorms and winter rain and snow. The mean annual temperature is 54 degrees F. Frost-free season is 180 to 240 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Anthony, Brazito, Gila, Grabe Hantz, and Queencreek and the competing Glendale soils. Anthony soils are coarse-loamy. Queencreek soils are sandy-skeletal. Brazito soils are sandy. Gila and Grabe soils are coarse-silty. Hantz soils are fine.
DRAINAGE AND PERMEABILITY: Well drained; runoff is medium; moderately slow permeability.
USE AND VEGETATION: Used for grazing and irrigated cropland. Alfalfa, cotton, grain, and vegetables are major irrigated crops. Native vegetation is mesquite, quailbush, creosotebush, squawbush, alkali sacaton, sixweeks grama, Indianwheat, alfileria, and annual weeds and grasses.
DISTRIBUTION AND EXTENT: Southern Arizona and southern New Mexico. Pima soils are moderately extensive. This soil occurs in LRR-D, MLRAs 40, 41, and 42.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Middle Gila Area, Arizona, 1917
REMARKS: Diagnostic horizons and features recognized in the Pima Series are:
1) No diagnostic horizons are recognized
2) Stratification is common feature in massive horizons
Fluvial feature - Irregular decrease in organic carbon in the zone from 25 to 60 inches (C1, C2 horizons)
Classified according to Soil Taxonomy, Second Edition, 1999.
Type location was moved from Santa Cruz County to Cochise County, Arizona.
ADDITIONAL DATA: NSS Laboratory sample S44AZ-003-001.