LOCATION COWAN AZEstablished Series
TAXONOMIC CLASS: Sandy, mixed, thermic Ustic Torrifluvents
TYPICAL PEDON: Cowan sandy loam, cultivated. (Colors are for dry soil unless otherwise noted.)
A1--0 to 2 inches; brown (7.5YR 5/4) sandy loam, dark reddish brown (5YR 3/4) moist; structureless, single grain; loose; many fine, medium and coarse roots; common very fine irregular pores; neutral (pH 7.0); clear smooth boundary. (1 to 3 inches thick)
C1--2 to 23 inches; reddish brown (5YR 4/4) light sandy loam, dark reddish brown (5YR 3/4) moist; structureless, massive; slightly hard, very friable; many fine, medium and coarse roots; many fine irregular pores, common very fine tubular pores; neutral (pH 7.0); abrupt wavy boundary. (16 to 30 inches thick)
C2--23 to 45 inches; reddish brown (5YR 5/4) loamy sand, reddish brown (5YR 4/4) moist; structureless, massive; slightly hard, very friable; few fine and medium roots; many fine and medium irregular pores; few fine gravel; moderately alkaline (pH 8.0); gradual wavy boundary. (18 to 30 inches thick)
C3--45 to 56 inches; brown (7.5YR 5/4) loamy sand, reddish brown (5YR 4/4) moist; structureless, massive; slightly hard, friable; few coarse roots; many fine and medium irregular and tubular pores; few fine gravel; slightly alkaline (pH 7.8). (8 to 12 inches thick)
TYPE LOCATION: Graham County, Arizona; 400 feet east and 25 feet north of the south quarter corner, Sec. 35, T. 11 S., R. 23 E.
RANGE IN CHARACTERISTICS:
Soil moisture - Intermittently moist in the soil moisture control section during July-August and December-January. Driest during May and June. Ustic aridic soil moisture regime.
Reaction: neutral to moderately alkaline
A horizon
Hue: 2.5YR, 5YR, and 7.5 YR
Value: 4 or 5 dry and 3 or 4 moist
Chroma: 3 or 6
Effervescence: none to strongly
C horizons:
Hue: 5YR or 2.5YR
Value: 4 through 6 dry, and 3 or 4 moist
Chroma: 4 through 6
Texture: stratified loamy sand, sandy loam, loamy coarse sand and containing some thin slightly finer or coarser textured strata. A few thin discontinuous strata weakly cemented with silica are in the substratum below depths of 36 inches.
Effervescence: slightly to strongly
COMPETING SERIES: These are the Horner (AZ) and Minneosa (NM) series. Horner soils have hues that are dominantly 7.5YR and yellower. Minneosa soils have 2C horizons of silt loam texture in the lower part of the profile. In addition, Minneosa soils are in LRR-G and are more moist in May and June.
GEOGRAPHIC SETTING: The Cowan soils are on flood plains and low terraces at elevations of 2,200 to 4,500 feet. Dominant slopes range from 0 to 3 percent. The climate is warm arid and semiarid continental. The mean annual temperature ranges from 58 degrees to 70 degrees F. The freeze-free period ranges from 160 to 260 days. The mean annual precipitation ranges from 12 to 14 inches. In some areas the precipitation is as low as 10 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cogswell, Comoro, McAllister, and White House series. Cogswell soils are fine textured and Comoro soils are moderately coarse textured. The McAllister and White House soils have argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained to excessively drained. Surface runoff is medium. Permeability is moderately rapid to rapid.
USE AND VEGETATION: Where the soil is not irrigated it is used for grazing when rainfall stimulates the growth of annual grasses. Irrigated areas are used for cropland and pasture. Native vegetation is blue grama and Rothrock grama, yucca, widely spaced mesquite and annual grasses.
DISTRIBUTION AND EXTENT: Southeastern Arizona and possibly southwestern New Mexico. Cowan soils are of small extent, but they are widespread in small bodies throughout southeastern Arizona. This soil occurs in LRR-D, MLRAs 40 and 41.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Cochise County, Arizona (Sulphur Spring Valley Area), 1942.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: the surface to 2 inches
Entisol feature - The absence of diagnostic subsurface horizons
Fluvial feature - Irregular decrease in organic carbon in the zone from 2 to 56 inches (C1, C2, C3 horizons)
Classified according to Soil Taxonomy Second Edition, 1999.
The classification was changed and errors in the description were corrected to match the published description in January 2002.