LOCATION TOLTEC AZEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, hyperthermic Typic Haplocalcids
TYPICAL PEDON: Toltec fine sandy loam. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 12 inches; pale brown (10YR 6/3) fine sandy loam, brown (10YR 4/3) moist; massive; slightly hard, friable, slightly sticky and nonplastic; common fine roots; common fine tubular pores; slightly effervescent; moderately alkaline (pH 8.2) abrupt smooth boundary. (4 to 12 inches thick)
Bw--12 to 24 inches; light brown (7.5YR 6/4) fine sandy loam, brown (7.5YR 4/4) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic; common very fine roots; common very fine tubular pores; strongly effervescent; moderately alkaline (pH 8.4); clear smooth boundary. (6 to 24 inches thick)
Bk--24 to 36 inches; light brown (7.5YR 6/4) very fine sandy loam, brown (7.5YR 4/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots, few very fine tubular pores; common fine soft lime masses; 15 percent pebbles that are silica-lime cemented pan fragments; violently effervescent; strongly alkaline (pH 8.6); clear wavy boundary. (10 to 14 inches thick)
2Bkq1--36 to 50 inches; pinkish gray (7.5YR 7/2) extremely gravelly fine sandy loam, light brown (7.5YR 6/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; common medium irregular lime masses; 85 percent pebbles composed of silica-lime cemented pan fragments; few fine roots; violently effervescent; strongly alkaline (pH 8.6); abrupt wavy boundary. (10 to 20 inches thick)
2Bkq2--50 to 60 inches; pinkish gray (7.5YR 7/2) very gravelly fine sandy loam, light brown (7.5YR 6/4) moist; massive; slightly hard, friable, slightly stick and slightly plastic; few fine roots; common fine rounded lime masses; few fine interstitial pores; 55 percent pebbles composed of silica-lime cemented pan fragments; violently effervescent; strongly alkaline (pH 8.8).
TYPE LOCATION: Pinal County, Arizona; 2440 feet west and 100 feet north of the southeast corner of sec. 24, T. 7 S., R. 7 E.
RANGE IN CHARACTERISTICS:
Soil moisture - Intermittently moist in some part of the soil moisture control section during July-September and December-February. Typic aridic moisture regime.
Soil temperature - 72 to 80 degrees F.
Rock fragments - Almost all are pan fragments; less than 15 percent in the upper story.
Texture of particle-size control section - Fine sandy loam, very fine sandy loam, sandy loam or loam; averages less than 20 percent clay.
Calcic horizon - Consists of an old disintegrated pan; the upper part is 80 to 95 percent silica-lime cemented pan fragments that are 1 to 10 cm in diameter; this part is from 12 to 24 inches thick; it begins at depths of 20 to 40 inches but usually is at about 36 inches; the lower part is similar but has about 50 percent soils material; calcium carbonate equivalent is 20 to 55 percent.
Organic matter content - less than 1 percent.
pH- 8.2 to 9.0.
Salinity- EC is less than 8 dS/m.
A horizon
Hue: 10YR or 7.5YR
Value: 5, 6, or 7 dry, 3 or 4 moist
Chroma: 2, 3, 4, or 5 dry, 3, 4, 5, or 6 moist
Texture: Fine sandy loam
Carbonates: Slightly effervescent to strongly effervescent
Bw horizon
Hue: 10YR or 7.5YR
Value: 5, 6, or 7 dry, 3, 4, or 5 moist
Chroma: 2, 3, 4, 5, or 6 dry and moist
Texture: Fine sandy loam, very fine sandy loam, sandy loam, or loam
Carbonates: Slightly effervescent to strongly effervescent.
Bk horizon
Hue: 10YR or 7.5YR
Value: 5, 6, or 7 dry, 3, 4, or 5 moist
Chroma: 2, 3, 4, 5, or 6 dry and moist
Texture: Fine sandy loam, very fine sandy loam, sandy loam, or loam
Carbonates: Strongly effervescent to violently effervescent; calcium carbonate equivalent is less than 5 percent in the upper part; 5 to 15 percent in lower part.
Bkq horizon
Hue: 10YR or 7.5YR
Value: 5, 6, or 7 dry, 4, 5, or 6 moist
Chroma: 2, 3, 4, 5, or 6 dry and moist
Texture: Extremely gravelly fine sandy loam and very gravelly fine sandy loam
COMPETING SERIES: These are the Aco (CA), Coolidge (AZ), Garywash (CA), Laveen (AZ), and Rillito (AZ) soils. These soils do not have a calcic horizon that consists of a disintegrated hardpan. In addition, Aco and Garywash soils are in the Colorado Desert portion of southeast California (MLRA 31) receive mostly winter precipitation and are usually dry April through November.
GEOGRAPHIC SETTING: Toltec soils are on fan terraces and relict basin floors. Slopes are 0 to 1 percent. These soils formed in fan alluvium and eolian loams over mixed alluvium. The average annual precipitation is 4 to 10 inches and occurs as thunderstorms from July to September and as gentle rains during December and January. The mean annual temperature is 67 to 75 degrees F. and the frost-free period is 240 to 325 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Casa Grande, Cipriano, Coolidge, Laveen, La Palma and Mohall soils. Casa Grande soils are deep, fine-loamy and have a natric horizon. Cipriano soils have more than 35 percent rock fragments and have a duripan at shallow depths. La Palma soils have argillic and petrocalcic horizons. Mohall soils are fine-loamy and have argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderate permeability.
USE AND VEGETATION: Under irrigation, alfalfa, cotton, grain sorghum, safflower, sugar beets, and citrus are grown on this soil. Native vegetation is mainly creosotebush, bush muhly, big galleta, plains bristlegrass, Arizona cottontop, range ratany, threeawn, little leaf paloverde, triangle leaf bursage, white bursage, staghorn cholla, greythorn, and saguaro.
DISTRIBUTION AND EXTENT: Southern and central Arizona. MLRA is 40. Toltec soils are inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Pinal County (Casa Grande Soil Survey Area), Arizona, 1936.
REMARKS: Diagnostic horizons and features recognized are:
Ochric epipedon - The zone from the surface to about 12 inches
Cambic horizon - The zone from about 12 to 24 inches.
Calcic horizon - The zone from about 24 to 60 inches.
Pan fragment feature - The soil has a 2Bk horizon that consists of more than 50 percent pan fragments. This material appears to be the remnants of a petrocalcic horizon that is disintegrating.
Classified according to Soil Taxonomy Second Edition, 1999; Keys to Soil Taxonomy Tenth Edition, 2006.