LOCATION PLAINTANK AZEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic, shallow Ustalfic Petrocalcids
TYPICAL PEDON: Plaintank extremely gravelly loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 2 inches; yellowish brown (10YR 5/4) extremely gravelly loam, dark yellowish brown (10YR 4/4) moist; weak medium platy structure parting to weak fine granular; soft, very friable, nonsticky and slightly plastic; common very fine roots; many very fine irregular pores; 60 percent gravel; violently effervescent; slightly alkaline (pH 7.8); abrupt smooth boundary. (1 to 3 inches thick)
Btk--2 to 12 inches; yellowish brown (10YR 5/4) gravelly loam, dark yellowish brown (10YR 4/4) moist; moderate medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine roots; common fine and few very fine tubular pores; 15 percent gravel; common distinct clay films in pores; few faint calcium carbonate coatings on ped faces and gravel; violently effervescent; moderately alkaline (pH 8.0); abrupt wavy boundary. (6 to 11 inches thick)
2Bk1--12 to 17 inches; yellowish brown (10YR 5/4) extremely cobbly loam, dark yellowish brown (10YR 4/4) moist; massive; hard, friable, slightly sticky and slightly plastic; few very fine roots; few very fine irregular pores; 15 percent gravel and 75 percent cobble-sized hardpan fragments; common prominent calcium carbonate pendants under fragments; violently effervescent; moderately alkaline (pH 8.0); abrupt wavy boundary. (5 to 10 inches thick)
2Bkm1--17 to 36 inches; laminar capped petrocalcic horizon; violently effervescent; clear wavy boundary. (8 to 24 inches thick)
3Bkm2--36 to 46 inches; pink (5YR 8/4) moderately cemented very gravelly sandy loam, pink (5YR 8/3) moist; weak medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few very fine roots in fractures; few very fine irregular pores; 40 percent gravel; violently effervescent, with calcium carbonate plugging pores and voids; abrupt wavy boundary. (6 to 14 inches thick)
3Bk--46 to 60 inches; brown (7.5YR 5/4) very gravelly sandy loam, brown (7.5YR 4/4) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; few very fine roots; few very fine irregular pores; 50 percent gravel; few distinct calcium carbonate masses and coatings on rock fragments; violently effervescent.
TYPE LOCATION: Mohave County, Arizona; on the Hualapai Indian Reservation; 2400 feet north and 500 feet east of the southwest corner of Section 11, T. 26 N., R. 12 W.; in Plain Tank Flat.
RANGE IN CHARACTERISTICS:
Soil moisture: Intermittently moist in some part of the soil moisture control section during December - February and July - September. Driest during May and June. Ustic aridic soil moisture regime.
Soil temperature: 54 to 57 degrees F.
Depth to petrocalcic horizon: 10 to 20 inches
Rock fragments: averages 35 to 60 percent fragments in the control section, but individual horizons may contain less than 35 percent
Clay content: averages 18 to 24 percent in control section
A horizon
Hue: 7.5YR, 10YR
Value: 4 through 6 dry, 3 or 4 moist
Btk horizon
Hue: 7.5YR, 10YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 4 through 6 dry, 3 through 6 moist
2Bk horizon
Hue: 7.5YR, 5YR
Value: 4 through 7 dry, 4 through 6 moist
Chroma: 4 through 6, dry or moist
Horizons underlying the petrocalcic horizon are variable in texture, and have weak to moderate cementation by calcium carbonate.
COMPETING SERIES: This is the Hollace (NV) series. Hollace soils have a petrocalcic horizon at shallow depth that is underlain by bedrock. In addition, Hollace soils are in the Great Basin Desert (MLRA 29) and have precipitation more evenly distributed throughout the year.
GEOGRAPHIC SETTING: Plaintank soils are on gently undulating fan terraces with slopes of 1 to 5 percent. These soils formed in alluvium derived dominantly from sedimentary and igneous rocks. Elevations are 4600 to 5000 feet. The mean annual air temperature is 52 to 55 degrees F. The mean annual precipitation is 10 to 12 inches. The frost-free period is 135 to 175 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Barx, Curhollow, Dean, Poley, Rolie, and Winona soils. Barx, Dean and Poley soils are very deep. Curhollow soils do not have argillic horizons and have a shallow petrocalcic horizon that overlies bedrock. Rolie soils do not have argillic horizons and contain less that 35 percent rock fragments in the control section. Winona soils do not have a petrocalcic horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderate permeability.
USE AND VEGETATION: Plaintank soils are used primarily for livestock grazing and wildlife habitat. The present vegetation is blue grama, bottlebrush squirreltail, needleandthread and winterfat.
DISTRIBUTION AND EXTENT: Northwestern Arizona. This series is of small extent. MLRA 35.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Mohave County, Arizona; Soil survey of the Hualapai-Havasupai Area, 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)
Argillic horizon - The zone from 2 to 12 inches (Btk horizon)
Petrocalcic horizon - The zone from 17 to 36 inches (2Bkm1 horizon)
Classified according to Soil Taxonomy Second Edition, 1999.