LOCATION TUCSON AZEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, hyperthermic Typic Calciargids
TYPICAL PEDON: Tucson loam - cultivated. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 14 inches; light brown (7.5YR 6/4) loam, reddish brown (5YR 4/4) moist; weak fine and medium blocky clods; hard, friable, slightly sticky and slightly plastic; many fine and medium roots; few very fine tubular pores; few fine gravel; violently effervescent; moderately alkaline (pH 8.3); clear smooth boundary. (7 to 16 inches thick)
Btk1--14 to 20 inches; yellowish red (5YR 5/6) clay loam, yellowish red (5YR 4/6) moist; weak and moderate fine subangular blocky structure; very hard, friable, slightly sticky and moderately plastic; many very fine and fine roots; common fine tubular pores; few faint clay films on faces of peds; few fine gravel; violently effervescent as common fine and medium irregular calcium carbonate masses; moderately alkaline (pH 8.3); clear smooth boundary. (4 to 15 inches thick)
Btk2--20 to 31 inches; yellowish red (5YR 4/6) clay loam, yellowish red (5YR 5/8) moist; moderate fine and medium subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; many fine and medium tubular pores; few faint clay films on faces of peds and lining pores;; violently effervescent as many fine and medium irregular calcium carbonate masses; moderately alkaline (pH 8.3); clear wavy boundary. (5 to 14 inches thick)
Btk3--31 to 36 inches; yellowish red (5YR 5/6) clay loam, reddish brown (5YR 4/4) moist; weak medium subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; many fine and medium tubular pores; few faint clay films lining pores; few gravel; violently effervescent as common fine irregular and rounded calcium carbonate masses; moderately alkaline (pH 8.2); clear smooth boundary. (4 to 10 inches thick)
Bk--36 to 60 inches; light brown (7.5YR 6/4) loam, brown (7.5YR 4/4) moist; weak medium and coarse subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common fine roots; few very fine and fine tubular pores; few fine, medium and coarse gravel; few medium gypsum crystals; violently effervescent as common fine irregular and rounded calcium carbonate masses; moderately alkaline (pH 8.2).
TYPE LOCATION: Maricopa County, Arizona; 2,260 feet north and 110 feet east of the southwest corner of section 32, T. 2 N., R. 8 W.
RANGE IN CHARACTERISTICS:
Soil moisture - Intermittently moist in some part of the soil moisture control section during July - September and December - February. Driest during May and June. Typic aridic soil moisture regime.
Soil temperature - 72 to 80 degrees F.
Depth to calcic horizon - Less than 20 inches; calcium carbonate equivalent ranges from 15 to 35 percent; depth to calcium carbonate accumulation is 4 to 16 inches.
Rock fragments - Averages less than 15 percent in the particle-size control section.
Desert Pavement - Some pedons have a surface cover of desert varnished gravel
Reaction - slightly to very strongly alkaline
A horizon
Hue: 10YR, 7.5YR, 5YR
Value: 5, 6 or 7 dry, 3 through 6 moist
Chroma: 2, 3, 4 or 6, dry or moist
Organic matter: Less than 1 percent
B horizon
Hue: 7.5YR, 5YR
Value: 4, 5, 6 or 7 dry, 3, 4 or 5 moist
Chroma: 4, 6 or 8, dry or moist
Texture: Loam, sandy clay loam, clay loam (20 to 35 percent clay)
Bk horizon
Hue: 7.5YR, 5YR
Value: 4, 5, 6 or 7 dry, 3, 4 or 5 moist
Chroma: 2, 3, 4 or 6, dry or moist
Texture: Loam, sandy loam, sandy clay loam, clay loam (15 to 35 percent clay)
Cementation: Weakly cemented in some pedons.
COMPETING SERIES: These are the Harqua (AZ), Mohall (AZ), Snaggletooth (CA), and Tremant (AZ) series. Mohall and Tremant soils have calcic horizons at depths of 20 to 40 inches. Harqua soils average more than 15 percent gravel in the control section. Snaggletooth soils are in the Colorado Desert of southeastern California (MLRA 31) and are moist in some part for short periods during winter and early spring.
GEOGRAPHIC SETTING: Tucson soils are on nearly level and gently sloping fan terraces, stream terraces or relict basin floors at elevations of 400 to 2200 feet. Slopes range from 0 to 3 percent. These soils formed in fan alluvium and stream alluvium from mixed sources. The mean annual air temperature ranges from 70 to 78 degrees F. The mean annual precipitation is 4 to 10 inches. The frost-free period is 250 to 325 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Harqua, Mohall, and Tremant soils and the Estrella, Gilman, and Toltec soils. Estrella soils are moderately deep over a buried Bt horizon. Gilman soils are medium textured and do not have argillic horizons. Toltec soils do not have argillic horizons and are coarse-loamy.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderately slow permeability.
USE AND VEGETATION: Used for livestock grazing and irrigated cropland. Vegetation is creosotebush, bursage, sixweeks grama, Indian wheat, Mormon tea, and cacti with scattered mesquite, ironwood, and paloverde trees. Irrigated areas are planted to cotton, alfalfa, small grains, citrus, fruits, grapes, vegetables, and other crops.
DISTRIBUTION AND EXTENT: Southern Arizona. Tucson soils are moderately extensive. MLRA is 40.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Pima County (Tucson Area), Arizona; 1931.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 14 inches (Ap horizon)
Argillic horizon - The zone from 14 to 36 inches (Btk1, Btk2, Btk3 horizons)
Calcic horizon - The zone from 14 to 60 inches (Btk1, Btk2, Btk3, Bk horizons)
Classified according to Soil Taxonomy Second Edition, 1999; Keys to Soil Taxonomy Tenth Edition, 2006.