LOCATION CASTO AZEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Aridic Haplustalfs
TYPICAL PEDON: Casto very gravelly sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 1 inch; dark grayish brown (10YR 4/2) very gravelly sandy loam, very dark grayish brown (10YR 3/2) moist; moderate fine granular structure; slightly hard, friable, slightly sticky, slightly plastic; many fine and medium roots; common fine interstitial and tubular pores; 70 percent fine, medium and coarse gravel and few cobbles; neutral (pH 6.6); abrupt smooth boundary. (1 to 3 inches thick)
Bt1--1 to 5 inches; dark grayish brown (10YR 4/2) gravelly sandy clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; hard, friable, sticky, plastic; many very fine, fine and medium roots; few fine tubular pores; few thin clay films on faces of peds and in pores; 20 percent gravel and 15 percent cobbles; neutral (pH 6.6); clear smooth boundary. (2 to 4 inches thick)
Bt2--5 to 11 inches; reddish brown (5YR 4/4) gravelly heavy sandy clay loam, reddish brown (5YR 4/4) moist; moderate medium and coarse subangular and angular blocky structure; very hard, firm, sticky, plastic; common fine and medium roots; few fine tubular pores; common moderately thick clay films on faces of peds and in pores; 25 percent gravel and 15 percent cobbles; moderately acid (pH 5.6); clear wavy boundary. (5 to 12 inches thick)
Bt3--11 to 16 inches; reddish brown (5YR 4/3) very gravelly sandy clay loam, reddish brown (5YR 4/3) moist; many medium and large distinct pinkish gray (7.5YR 7/2) mottles, brown (7.5YR 5/2) moist, mottles appear to be weathered gravel; moderate medium and coarse subangular and angular blocky structure; very hard, firm, sticky, plastic; common fine and medium roots; few fine tubular pores; common moderately thick clay films on faces of peds and in pores; 35 percent gravel and 15 percent cobbles; moderately acid (pH 5.6); clear wavy boundary. (4 to 12 inches thick)
Bt4--16 to 22 inches; pinkish gray (7.5YR 7/2) and reddish brown (5YR 4/4) very gravelly sandy clay loam, brown (7.5YR 5/2) and reddish brown (5YR 4/4) moist; weak fine and medium subangular blocky structure; very hard, firm, sticky, plastic; few fine and medium roots; common moderately thick clay films on faces of peds and in pores; 35 percent gravel and 15 percent cobbles; neutral (pH 6.6); clear wavy boundary. (5 to 15 inches thick)
Bt5--22 to 28 inches; pinkish gray (7.5YR 7/2) and reddish brown (5YR 4/4) very gravelly sandy clay loam, light brown (7.5YR 6/4) and reddish brown (5YR 4/4) moist; massive; very hard, firm, sticky, plastic; few fine roots; common moderately thick clay films on surface of pebbles; 60 percent gravel and 10 percent cobbles; slightly effervescent in spots; slightly alkaline (pH 7.4); clear irregular boundary. (5 to 8 inches thick)
Bk1--28 to 45 inches; pinkish white (7.5YR 8/2) very gravelly sandy loam, brown (7.5YR 5/2) moist; massive; hard, friable, slightly sticky, slightly plastic; 60 percent gravel and 10 percent cobbles; slightly effervescent; moderately alkaline (pH 8.0); diffuse wavy boundary. (15 to 20 inches thick)
Bk2--45 to 60 inches; pinkish white (7.5YR 8/2) very gravelly sandy loam, brown (7.5YR 5/2) moist; massive; hard, friable, slightly sticky, slightly plastic; 50 percent gravel and 10 percent cobbles; strongly effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Cochise County, Arizona; 500 feet south and 700 feet east of W1/4 corner of sec. 8, T.23S., R.19E.
RANGE IN CHARACTERISTICS:
Soil moisture: Aridic ustic moisture regime
Depth to the Bk horizon is greater than 24 inches.
Mean annual soil temperature: 52 degrees to 59 degrees F.
These soils are noncalcareous in the upper part of the solum but are calcareous in the lower part of the Bt horizon and in the Bk horizon.
A horizon
Hue: 7.5YR or 10YR
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 2 through 4
Rock fragments: contains few to over 50 percent rock fragments cobbles are common the surface.
Bt horizon
Hue: 10YR through 5YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 2 through 6 but dominantly 4 through 6
Mottles have value of 7 dry and 5 moist
Texture: gravelly clay loam, very gravelly clay loam, gravelly sandy clay loam, and very gravelly sandy clay loam.
Bk horizon
Texture: very gravelly clay loam, very gravelly sandy loam, and cobbly or very gravelly sandy clay loam.
CaC03 content: 1 to 8 percent
COMPETING SERIES: These are the Espirtu (NM),
Snavee (WY),
Tsezhin (AZ),
Wauquie (NM) and
Wetoe (CO) series.
Espiritu soils formed in gravelly alluvium, colluvium and residuum and are on mesas, mountain slopes, landslides of escarpments and dissected pediments.
Snavee soils have the base of the argillic horizon at depths less than 10 inches, have less than 18 percent clay in the particle size control section and have soil temperature less than 50 degrees
Tsezhin soils have a calcic horizon and will be classified as Calcidic subgroup on update.
Wauquie soils are moist in all parts of the soil moisture control section for 30 to 40 days consecutively during the 120 days following the winter solstice.
Wetoe soils are noncalcareous.
GEOGRAPHIC SETTING: Casto soils are on rolling to steep old alluvial fans at elevations of 5,000 to 6,500 feet. These soils formed in old gravelly alluvium from andesite, quartzite, shale, and possibly diorite. Average annual precipitation is 16 to 22 inches. The mean annual temperature ranges from 50 degrees to 57 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Canelo, Faraway, Luzena, and White House soils and the competing Martinez soils. Canelo soils are somewhat poorly drained, lack a Bk horizon, and are clayey-skeletal. Faraway and Luzena soils have mollic epipedons and have bedrock at depths of 20 inches or less. White House soils have less than 35 percent rock fragments in the series control section and mean annual soil temperatures of 59 degrees F. or more.
DRAINAGE AND PERMEABILITY: Well-drained; medium to rapid runoff; slow permeability.
USE AND VEGETATION: These soils are used mainly for range and wildlife. Native vegetation is Emory oak, pinyon pine, juniper, manzanita, Arizona cottontop, sideoats, slender and blue grama, ring muhly, bluestem, plains lovegrass, three-awn, curly mesquite, and canebeardgrass.
DISTRIBUTION AND EXTENT: Santa Cruz and Cochise Counties, Arizona. These soils are moderately extensive. MLRA 41.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Santa Cruz County Area, Arizona, 1971.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 1 inch (A horizon)
Argillic horizon - The zone from 1 to 28 inches (Bt horizons)
Classified according to Keys to Soil Taxonomy Ninth Edition, 2003.
Classification changed from Udic Haplustalfs to Aridic Haplustalfs in 2006.