LOCATION DIASPAR AZEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, thermic Ustic Haplargids
TYPICAL PEDON: Diaspar sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 2 inches; light brown (7.5YR 6/4) sandy loam, brown (7.5YR 4/4) moist; weak thin platy structure; loose, very friable, nonsticky and nonplastic; many very fine roots; common very fine interstitial pores; 10 percent gravel; slightly acid; abrupt smooth boundary.
BA--2 to 9 inches; brown (7.5YR 5/4) gravelly sandy loam, dark brown (7.5YR 3/4) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and common fine roots; common very fine tubular pores; 30 percent gravel; slightly acid; clear wavy boundary.
Bt1--9 to 21 inches; yellowish red (5YR 5/6) gravelly sandy loam, yellowish red (5YR 4/6) moist; weak medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; many very fine roots; common very fine tubular pores; common faint clay films lining pores and bridging sand grains; 30 percent gravel; slightly alkaline; clear wavy boundary.
Bt2--21 to 28 inches; yellowish red (5YR 5/6) gravelly sandy loam, yellowish red (5YR 4/6) moist; weak medium prismatic structure; hard, firm, moderately sticky and moderately plastic; many very fine roots; common very fine tubular pores; 30 percent gravel; common faint clay films bridging sand grains and lining pores; moderately alkaline; clear wavy boundary.
2Bt--28 to 41 inches; reddish yellow (5YR 6/6) sandy clay loam, yellowish red (5YR 4/6) moist; weak medium prismatic structure; hard, firm, moderately sticky and moderately plastic; common very fine roots; common very fine tubular pores, 10 percent gravel; many distinct clay films on faces of peds and lining pores; many fine iron and manganese stains and masses; slightly effervescent; moderately alkaline; clear wavy boundary.
3BCt--41 to 46 inches; light yellowish brown (10YR 6/4) gravelly loam, dark yellowish brown (10YR 4/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; many very fine tubular pores; few faint clay films lining pores; 30 percent gravel; moderately alkaline; clear wavy boundary.
3C--46 to 60 inches; light yellowish brown (10YR 6/4) very gravelly loam, dark yellowish brown (10YR 4/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; many very fine tubular pores; 50 percent gravel; slightly effervescent moderately alkaline
TYPE LOCATION: Pima County, Arizona; about 550 feet north and 100 feet west of the southeast corner of sec. 35, T.19 S., R.8 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 - 0 to 72 degrees F.
Rock fragments - Averages 10 to 35 percent gravel in the particle-size control section
A and BA horizons
Hue: 7.5YR, 5YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 3 to 6, dry or moist
Reaction: moderately acid to neutral
Organic matter: less than 1 percent
Bt horizon
Hue: 2.5YR, 7.5YR
Value: 3 to 6 dry, 3 to 5 moist
Chroma: 3 to 6, dry or moist
Texture: sandy loam, loam, fine sandy loam, sandy clay loam (averages less than 18 percent clay and more than 50 percent sand)
Calcium carbonate equivalent: 0 to 5 percent
Reaction: neutral to moderately alkaline
C horizon
Hue: 5YR to 10YR
Value: 4 to 7 dry, 4 to 6 moist
Chroma: 2 to 6, dry or moist
Texture: sandy loam, loam, fine sandy loam, loamy fine sand, loamy sand, sand (5 to 18 percent clay)
Calcium carbonate equivalent: 0 to 5 percent
Buried horizons - some pedons have a buried argillic horizon below 40 inches.
COMPETING SERIES: This is the Summerford (NM) series. Summerford soils have secondary calcium carbonate accumulations in the lower profile.
GEOGRAPHIC SETTING: Diaspar soils are on gently sloping to sloping fan terraces at elevations of 3,000 to 5,200 feet. Slopes range from 0 to 8 percent. These soils formed in fan alluvium from rhyolite, granite, gneiss, schist, quartzite and andesite. The mean annual precipitation is 12 to 16 inches. The mean annual air temperature is 59 to 68 degrees F. The frost-free period is 180 to 240 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Courtland, Cowan, and Sasabe soils. Courtland soils are fine-loamy. Cowan soils do not have argillic horizons. Sasabe soils are fine.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderately rapid or moderate permeability.
USE AND VEGETATION: Used for livestock grazing and irrigated cropland. Vegetation is sideoats grama, black grama, sand dropseed, Arizona cottontop, and cane bluestem. Common irrigated crops are cotton, corn, small grains and alfalfa.
DISTRIBUTION AND EXTENT: Southern Arizona. Diaspar soils are moderately extensive. MLRA is 41.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Pima County, Arizona; Soil Survey of Pima County, Arizona, Eastern Part; 1986.
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 9 to 53 inches (Bt1, Bt2, Bt3, 2Btk1, 2Btk2 horizons)
Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Tenth Edition, 2006
The type location was moved to Pima County in 2003.