LOCATION MILKWEED AZEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic, shallow Petrocalcic Calciustepts
TYPICAL PEDON: Milkweed extremely gravelly loam - grazeable woodland. (Colors are for dry soil unless otherwise noted.)
A--0 to 2 inches; dark yellowish brown (10YR 4/4) extremely gravelly loam, dark brown (10YR 3/3) moist; weak thick platy structure parting to weak fine granular; soft, very friable, slightly sticky and slightly plastic; many very fine roots; many very fine irregular pores; 80 percent gravel as surface layer; violently effervescent, 27 percent calcium carbonate equivalent; slightly alkaline (pH 7.8); abrupt smooth boundary. (1 to 4 inches thick)
Bk1--2 to 8 inches; brown (10YR 4/3) very gravelly loam, dark brown (10YR 3/3) moist; weak medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine, many fine, and few medium roots; common very fine and few fine tubular pores; 40 percent gravel; few thin calcium carbonate coatings on rock fragments; violently effervescent, 16 percent calcium carbonate equivalent; moderately alkaline (pH 8.0); clear smooth boundary. (2 to 7 inches thick)
Bk2--8 to 11 inches; dark yellowish brown (10YR 4/4) very gravelly loam, dark yellowish brown (10YR 3/4) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine, common fine, few medium and coarse roots; common very fine and fine tubular pores; 45 percent gravel and 5 percent cobble, with few hardpan fragments; common thin calcium carbonate coatings on rock fragments; violently effervescent, 23 percent calcium carbonate equivalent; moderately alkaline (pH 8.0); abrupt wavy boundary. (3 to 8 inches thick)
2Bkm1--11 to 28 inches; thin bedded, laminar capped, calcium carbonate cemented hardpan; widely fractured in upper 3 inches; few fine and medium roots in fractures; abrupt wavy boundary. (9 to 15 inches thick)
2Bkm2--28 to 60 inches; extremely hard, indurated, calcium carbonate cemented hardpan.
TYPE LOCATION: Mohave County, Arizona; on the Hualapai Indian Reservation; 1600 feet north and 2400 feet east of the southwest corner of section 13, T.26 N., R.14 W.; approximately 1.5 miles northwest of Westwater Canyon, near Buckndoe Road.
RANGE IN CHARACTERISTICS:
Soil Moisture: Moist in some part of the soil moisture control section during December through March and intermittently moist during July through September. Driest during May and June. Aridic ustic soil moisture regime.
Soil Temperature: 54 to 56 degrees F.
Rock Fragments: averages more than 35 percent cobble and gravel in the control section
Depth to calcic horizon: 2 to 20 inches
Depth to Petrocalcic horizon: 10 to 20 inches
Calcium carbonate equivalent: Averages 15 to 40 percent in the calcic horizon
A horizon
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 3 or 4, dry or moist
Rock fragments, as a surface layer, range from 60 to 90 percent
Bk horizon
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 3 or 4, dry or moist
Textures: loam, fine sandy loam, sandy loam
Rock fragment content averages 35 to 60 percent, dominantly gravel-size
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Milkweed soils are on fan terraces of plateaus at elevations of 4600 to 5500 feet. These soils formed in tertiary alluvium derived dominantly from sedimentary and igneous rocks. Slopes range from 2 to 20 percent. The mean annual precipitation is 14 to 18 inches. The mean annual air temperature is 52 to 54 degrees F. The frost-free period is 120 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Buckndoe, Cabezon, Deama, Lykorly, Thunderbird and Wodomont soils. Cabezon soils are clayey and shallow to basalt. Deama soils have carbonatic mineralogy and are shallow to limestone. Lykorly soils are very deep with fine-loamy control sections. Buckndoe soils are very deep. Thunderbird soils are fine textured and moderately deep to basalt. Wodomont soils are shallow to limestone.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderate permeability.
USE AND VEGETATION: Milkweed soils are used for grazeable woodland, fuelwood production, and wildlife habitat. The present vegetation is single leaf pinyon, Utah juniper, banana yucca, Fremont barberry, desert ceanothus, cliffrose, bottlebrush squirreltail and blue grama.
DISTRIBUTION AND EXTENT: Northwestern Arizona. This series is not extensive. MLRAs are 35 and 39.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Mohave County, Arizona; Soil survey of Hualapai-Havasupai Area, Arizona, Parts of Coconino, Mohave and Yavapai Counties; 1993.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 2 inches (A horizon)
Calcic horizon - The zone from 2 to 11 inches (Bk1, Bk2 horizons)
Petrocalcic horizon - The zone from 11 to 60 inches (2Bkm1, 2Bkm2 horizons)
Classified according to Keys to Soil Taxonomy Ninth Edition, 2003.