LOCATION ALSCO AZEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Ustic Calciargids
TYPICAL PEDON: Alsco extremely cobbly sandy loam-rangeland (colors are for dry soil unless otherwise noted).
A--0 to 2 inches; dark yellowish brown (10YR 4/4) extremely cobbly sandy loam, dark yellowish brown (10YR 4/4) moist; weak thin platy structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots; common fine vesicular and many very fine and fine interstitial pores; 50 percent cobbles, 25 percent gravel and l5 percent stones; slightly alkaline (pH 7.5); abrupt wavy boundary (2 to 4 inches thick).
Bt--2 to 5 inches; brown (7.5YR 4/4) extremely cobbly sandy clay loam, dark brown (7.5YR 3/4) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine interstitial and common very fine and fine tubular pores; few thin clay films on faces of peds and in pores; 40 percent cobbles and 30 percent gravel; slightly alkaline (pH 7.8); clear wavy boundary (2 to 4 inches thick).
Btk1--5 to 11 inches; brown (7.5YR 4/4) very cobbly clay loam, dark brown (7.5YR 3/4) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; many very fine and fine roots; many very fine and fine interstitial and common very fine and fine tubular pores; common thin clay films on faces of peds and in pores; 30 percent cobbles and 25 percent gravel; few fine lime segregations on underside of rock fragments; strongly effervescent (5 percent calcium carbonate); moderately alkaline (pH 8.2); clear wavy boundary (6 to l4 inches thick).
Btk2--11 to l6 inches; brown (7.5YR 5/4) very cobbly clay loam, brown (7.5YR 4/4) moist; weak fine subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine and fine and few medium roots; many very fine and fine interstitial and common very fine and fine tubular pores; few thin clay films on faces of peds; 30 percent cobbles and 25 percent gravel; few fine lime segregations on faces of peds and thin coatings on rock fragments; strongly effervescent (6 per cent calcium carbonate); moderately alkaline (pH 8.4); clear wavy boundary (5 to 8 inches thick).
Bk1--l6 to 21 inches; light brown (7.5YR 6/4) very gravelly loam, brown (7.5YR 4/4) moist; massive; slightly hard, friable, slightly sticky and nonplastic; common very fine and fine roots; many very fine interstitial pores; 45 percent gravel; common fine lime veins and very few fine white (N 8/) soft lime masses; strongly effervescent (7 percent calcium carbonate); moderately alkaline (pH 8.4); abrupt wavy boundary (5 to 8 inches thick).
Bk2--21 to 26 inches; pinkish white (7.5YR 8/2) very cobbly sandy loam, pink (7.5YR 7/4) moist; massive; very hard, friable, nonsticky and nonplastic; few very fine and fine roots; common very fine tubular and interstitial pores; 40 percent cobbles and 30 percent gravel; violently effervescent (2l percent calcium carbonate); weak carbonate cementation; moderately alkaline (pH 8.4); clear wavy boundary (4 to 6 inches thick).
Bk3--26 to 35 inches; light brown (7.5YR 6/4) very cobbly sandy loam, brown (7.5YR 5/4) moist; massive; hard, friable, nonsticky and nonplastic; very few very fine roots; common very fine interstitial and few very fine tubular pores; 40 percent cobbles and 30 percent gravel; strongly effervescent; strongly alkaline (pH 8.6); gradual wavy boundary (8 to l2 inches thick).
Bk4--35 to 60 inches; light brown (7.5YR 6/4) very cobbly sandy loam, brown (7.5YR 5/4) moist; massive; hard, friable, nonsticky and nonplastic; common very fine interstitial pores; 45 percent cobbles and 25 percent gravel; strongly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Graham County, Arizona; approximately 9 miles southwest of the town of Pima, just southeast of Goat Hill; l,l00 feet south and l,900 feet east of the NW corner of sec. 29, T. 7 S., R. 24 E.
RANGE IN CHARACTERISTICS:
Depth to the calcic horizon: 20 to 30 inches
Rock fragments: averages greater than 35 percent rock fragments
Soil moisture: these soils are dry more than half the time. Ustic aridic moisture regime
Mean annual soil temperature: 57 1/4 to 7l 1/4 F.
Organic matter content: l to 2 percent in the surface, 5 inches and less than l percent in the subsoil.
A horizon
Hue: l0YR, 7.5YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 4
Texture: sandy loam, loam
Rock fragments: 35 to 90 percent rock fragments, dominated by cobbles. Some pedons have a stony surface
Reaction: slightly acid to slightly alkaline
Btk horizon
Hue: 7.5YR, l0YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 4
Texture: clay loam with 35 to 90 percent rock fragments, dominated by cobbles.
Effervescent: the upper part of the B2t horizon is noneffervescent and the lower part is strongly effervescent
Calcium carbonate: less than l0 percent
Reaction: moderately alkaline.
Bk horizon
Hue: 7.5YR, l0YR
Value: 6 to 8 dry, 5 to 7 moist
Chroma: l to 4
Texture: sandy loam
Reaction: 35 to 80 percent rock fragments, dominated by cobbles
Cementation: weakly to moderately cemented
Calcium carbonate: more than l5 percent
COMPETING SERIES: These are the Beewon (TX), Nolam (NM) and Throne (AZ) series. Bewon and Nolam soils have 7.5YR and redder hues. Throne and Beewon soils are inactive.
GEOGRAPHIC SETTING: Alsco soils are on convex side slopes and narrow ridges of gently sloping to steep alluvial fans adjacent to steep mountains at elevations of 3,500 to 5,000 feet. Slopes range from 5 to 60 percent. These soils formed in extremely cobbly and stony alluvium from granite and gneiss. The climate is semiarid continental. Mean annual air temperature ranges from 60 1/4 to 68 1/4 F., and mean annual precipitation ranges from l0 to l4 inches. The frost-free period is l80 to 220 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Maloy (T) and Pinaleno soils and the Comoro, Eba, Eloma (T), Santo Tomas, and Selevin (T) soils. Comoro soils are coarse-loamy. Eba, Eloma (T), and Selevin (T) soils are clayey-skeletal. Santo Tomas soils lack an argillic horizon.
DRAINAGE AND PERMEABILITY:
USE AND VEGETATION: Used for livestock grazing. Native vegetation is black grama, sideoats grama, bush muhly, slim tridens, Arizona cottontop, threeawn, spike pappusgrass, and Rothrock grama. The shrub species include creosotebush, whitethorn, ocotillo, wolfberry, brittlebush, mesquite, catclaw, false mesquite, and cacti.
DISTRIBUTION AND EXTENT: Southeastern Arizona and possibly southwest New Mexico. Alsco soils are of small extent. MLRA 41.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Gila-Duncan Area, Graham County, Arizona; 1979.
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 16 inches (Bt & Btk horizons)
Calcic horizon - the zone from 21 to 26 inches (Bk2 horizon)
Classified according to Keys to Soil Taxonomy, Tenth Edition, 2006
ADDITIONAL DATA:
Carbonates were run with field calcimeter method.
Updated competing series section 3/18/08, CEM