LOCATION TUBAC AZEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Typic Paleargids
TYPICAL PEDON: Tubac fine sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 2 inches; light brown (7.5YR 6/4) fine sandy loam, brown (7.5YR 4/4) moist; weak medium and thick platy structure; slightly hard, very friable, slightly sticky and slightly plastic; common fine and medium roots; few fine tubular and many fine irregular pores; 10 percent fine gravel; moderately acid (pH 5.8); abrupt smooth boundary. (1 to 3 inches thick)
A2--2 to 6 inches; reddish brown (5YR 5/3) gravelly fine sandy loam, reddish brown (5YR 4/3) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; few fine tubular and common fine irregular pores; 30 percent fine gravel; slightly acid (pH 6.3); clear smooth boundary. (4 to 11 inches thick)
A3--6 to 11 inches; reddish brown (5YR 5/3) gravelly sandy loam, reddish brown (5YR 4/3) moist; weak fine and medium subangular blocky structure; hard, friable, sticky and plastic; common fine and medium roots; common fine tubular and many fine irregular pores; few faint clay films on faces of peds and lining pores; 30 percent fine gravel; neutral (pH 7.0); abrupt wavy boundary. (1 to 5 inches thick)
Bt--11 to 21 inches; reddish brown (5YR 4/3) gravelly clay, reddish brown (5YR 4/4) moist; moderate medium prismatic structure parting to moderate fine and medium angular blocky; very hard, friable, sticky and very plastic; common fine roots; few fine tubular pores; many faint clay films on faces of peds and lining pores; 20 percent fine and medium gravel; slightly alkaline (ph 7.6); clear wavy boundary. (5 to 10 inches thick)
Btk1--21 to 35 inches; reddish brown (5YR 5/4) and pink (5YR 7/3) gravelly clay, reddish brown (5YR 4/4) and light reddish brown (5YR 6/3) moist; massive parting to moderate fine and medium angular blocky structure; very hard, friable, sticky, and plastic; few fine roots; common fine tubular and many fine irregular pores; many faint clay films on faces of peds and lining pores; slightly effervescent as common fine soft accumulations and thin discontinuous calcium carbonate coatings on rock fragments; 30 percent fine, medium, and coarse gravel; moderately alkaline (pH 8.2); gradual wavy boundary. (8 to 15 inches thick)
Btk2--35 to 44 inches; reddish brown ( 5YR 5/3) and reddish brown 5YR 5/4) gravelly sandy clay loam, reddish brown (5YR 4/4) moist; massive; very hard, friable, sticky, and plastic; few fine roots; common fine irregular and tubular pores; few faint clay films on faces of peds and lining pores; 30 percent fine, medium and coarse gravel and 5 percent cobble; slightly effervescent; slightly alkaline (pH 7.6); gradual wavy boundary. (10 to 25 inches thick)
2C--44 to 60 inches; light reddish brown (5YR 6/3) very gravelly loamy sand, reddish brown (5YR 4/3) moist; massive; very hard, friable, nonsticky and nonplastic; many fine irregular pores, slightly alkaline (pH 7.6).
TYPE LOCATION: Cochise County, Arizona; 9 miles north and .75 miles east of Willcox: 820 feet west and 2,265 feet south of the northeast corner of Sec. 18, T. 12 S., R. 25 E. Latitude of 32 degrees, 23 minutes, 30 seconds N. and Longitude of 109 degrees, 49 minutes, 40 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Soil Moisture: Intermittently moist in some part of the soil moisture control section during July-September and December-March. Driest during May and June. Typic aridic soil moisture regime.
Rock Fragments: Averages 25 percent in the control section; ranges to 40 percent in any one horizon
Clay Content: Averages more than 35 percent in the control section
Soil Temperature: 59 to 72 degrees F.
Calcium carbonate equivalent: Averages less than 15 percent in the control section
A horizon
Hue: 5YR, 7.5YR
Value: 4 through 7 dry, 3 though 6 moist
Chroma: 2, 3, or 4, dry or moist
Reaction: Moderately acid to slightly alkaline
B horizon
Hue: 2.5YR, 5YR, 7.5YR
Value: 3 through 8 dry, 3 through 6 moist
Chroma: 2 through 6, dry or moist
Texture: clay, clay loam, sandy clay loam, sandy clay; can range to include coarser textures
Reaction: slightly alkaline or moderately alkaline
COMPETING SERIES: This is the Schnebly (AZ) series. Schnebly soils have bedrock at depths of 20 to 40 inches.
GEOGRAPHIC SETTING: Tubac soils are on fan terraces and have slopes of 0 to 8 percent. These soils are formed in alluvium from mixed sources. Elevation ranges from 1,800 to 4,500 feet. The mean annual precipitation is 8 to 12 inches. The mean annual air temperature is 57 to 70 degrees F. The frost-free period is 240 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Comoro and Sahuarita series. These soils are coarse-loamy.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; slow permeability.
USE AND VEGETATION: Tubac soils are used for livestock grazing and irrigated cropland. The present vegetation is mesquite, burroweed, snakeweed, Arizona cottontop, threeawn, Rothrock grama, bush muhly, and annual and perennial grasses.
DISTRIBUTION AND EXTENT: Southern Arizona. This series is extensive. Total extent is about 257,000 acres. MLRAs are 40 and 41.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Nogales Area, Santa Cruz County, Arizona; 1930.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 11 inches (A1, A2, A3 horizons)
Argillic horizon - the zone from 11 to 44 inches (Bt, Btk1, Btk2 horizons)
Abrupt textural change - the boundary at 11 inches that has an increase of 41 percent clay.
The type location has been moved to a site referenced by Guy D. Smith and Klaus W. Flach as representative of the Paleargids great group. This historic reference point was used in the development of Soil Taxonomy and will have been preserved, PDC.
Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Tenth Edition, 2006.
Revised for the correlation of AZ661, 2/2009, WWJ
ADDITIONAL DATA: NSSL Sample S64AZ-003-028