LOCATION PINAL AZEstablished Series
TAXONOMIC CLASS: Loamy, mixed, superactive, hyperthermic, shallow Typic Haplodurids
TYPICAL PEDON: Pinal gravelly loam, range. (Colors are for dry soil unless otherwise noted.)
A--0 to 5 inches; light brown (7.5YR 6/4) gravelly loam, brown (7.5YR 4/4) moist; weak medium platy structure; slightly hard, friable, slightly sticky, slightly plastic; few very fine roots; few very fine interstitial pores; 20 percent gravel; strongly effervescent; moderately alkaline (pH 8.2); clear wavy boundary. (1 to 5 inches thick)
Bk--5 to 18 inches; light brown (7.5YR 6/4) gravelly loam, brown (7.5YR 4/4) moist; massive; hard, friable, slightly sticky, plastic; few very fine roots; many very fine tubular pores; 20 percent gravel; violently effervescent, with few fine distinct very pale brown (10YR 8/2) irregularly shaped soft lime bodies; moderately alkaline (pH 8.4); abrupt wavy boundary. (3 to 15 inches thick)
2Bkqm--18 to 28 inches; very pale brown (10YR 8/3) silica-lime indurated duripan, with common coarse distinct brown (7.5YR 5/4) seams and coatings, and common coarse and very coarse faint yellow (10YR 8/6) opalescent coatings, very pale brown (10YR 7/3) moist; massive; extremely hard, extremely firm; few interstitial pores along laminar surfaces; many thin (less than 5mm) and occasional moderately thick (5 to 20mm) continuous horizontal laminae; violently effervescent with thin (less than 5mm) white (10YR 8/1) and very pale brown (10YR 8/2) lime-cemented laminae interbedded with the silica laminae and lime coatings on silica laminar surfaces; moderately alkaline (pH 8.4).
TYPE LOCATION: Maricopa County, Arizona; 940 feet west and 940 feet north of SE corner of sec. 6, T.1N., R.6E.
RANGE IN CHARACTERISTICS:
Depth to the duripan: averages about 12 to 18 inches and ranges from 4 to 20 inches
Mean annual soil temperature: 72 degrees to 80 degrees F.
Soil moisture: These soils are usually dry, mainly during the spring and fall months. Typic aridic moisture regime.
Organic matter content: less than 1 percent organic matter
Reaction: moderately alkaline to strongly alkaline
Texture: gravelly loam, loam or gravelly very fine sandy loam
Clay content: averages less than 18 percent clay
Rock fragments: few to 35 percent gravel and cobbles by volume, some or all of which may be pan fragments.
A horizon
Hue: 10YR or 7.5YR
Value: 5 through 7 dry and 4 and 5 moist
Chroma: 3 or 4
Bk and Bkqm horizons
Hue: 10YR of 7.5YR
Value: 6 through 8 dry and 4 through 7 moist
Chroma: 1 through 4
Bkqm horizon
Thickness: 4 to 16 inches thick, but can consist of a series of layers 6 to 8 inches thick separated by marly soil material
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Pinal soils are on nearly level to moderately sloping old alluvial fans and terraces at elevations of 400 to 2,500 feet. Slope gradients range from 0 to 9 percent. The soils developed in medium-textured nongravelly or gravelly alluvium derived from mixed rock sources but mainly tuffs, rhyolite and volcanic ash. The climate is warm, arid, and continental. Mean annual temperature ranges from 67 degrees to 76 degrees F. and mean annual precipitation ranges from 3 to 10 inches. The frost-free season ranges from 250 to 350 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Antho, Contine, Gilman, Laveen, Mohall, Rillito, and Tremant soils, and the competing Cavelt and Toltec soils. Antho and Gilman soils lack indurated horizons and have loamy C horizons. Contine, Mohall and Tremant soils have argillic horizons. Laveen and Rillito soils have calcic horizons and do not have indurated C horizons.
DRAINAGE AND PERMEABILITY: Well-drained; slow or medium runoff; moderate permeability in the upper part and very slow permeability in the duripan.
USE AND VEGETATION: Used mainly as rangeland with limited areas being cultivated. Native vegetation is creosotebush, a few mesquite trees and annual grasses and forbs. Cultivated crops include vegetables and citrus which are planted after the soils have been modified by blasting or ripping.
DISTRIBUTION AND EXTENT: Southern Arizona. Pinal soils are moderately extensive. MLRA 40.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Middle Gila Valley Area, Arizona, 1917.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 5 inches (A horizon)
Duripan- The zone from 18 to 28 inches (Bkqm horizon)
Classified according to Keys to Soil Taxonomy Tenth Edition, 2006.
The series was placed on the inactive list in 1965. The series was reactivated in 1969.
The Pinal soils were formerly classified as Maximal Calcisols and described as having an indurated caliche hardpan.