LOCATION SONOITA AZ+NMEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, thermic Typic Haplargids
TYPICAL PEDON: Sonoita gravelly sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 2 inches; brown (7.5YR 5/4) gravelly sandy loam, brown (7.5YR 4/4) moist; weak medium platy structure; slightly hard, very friable, nonsticky and nonplastic; many fine roots; few medium tubular pores; 20 percent pebbles; moderately acid (pH 6.0); abrupt smooth boundary. (1 to 3 inches thick)
A2--2 to 4 inches; brown (7.5YR 5/4) gravelly sandy loam, reddish brown (5YR 4/4) moist; massive; hard, very friable, nonsticky and nonplastic; many very fine and fine roots; common fine interstitial and few very fine and fine tubular pores; 20 percent fine pebbles; neutral (pH 7.3); clear smooth boundary. (2 to 9 inches thick)
AB--4 to 10 inches; reddish brown (5YR 5/4) gravelly sandy loam, dark reddish brown (5YR 3/4) moist; weak fine subangular blocky structure; hard, friable, slightly sticky and nonplastic; common fine roots; common fine tubular pores; 15 percent fine pebbles; slightly alkaline (pH 7.8); clear wavy boundary. (5 to 15 inches thick)
BA--10 to 17 inches; reddish brown (5YR 5/4) gravelly sandy loam, dark reddish brown (5YR 3/4) moist; weak fine subangular blocky structure; hard, friable, slightly sticky and nonplastic; common fine roots; common fine tubular pores; 20 percent pebbles; slightly alkaline (pH 7.8); clear wavy boundary. (6 to 12 inches thick)
Bt--17 to 26 inches; reddish brown (5YR 5/4) gravelly sandy loam, yellowish red (5YR 4/6) moist; weak medium subangular blocky structure; hard, friable, slightly sticky and nonplastic; common fine roots; few fine tubular pores; common thin clay films on faces of peds; 20 percent pebbles; few cobbles; slightly effervescent in spots; moderately alkaline (pH 8.0); clear wavy boundary. (7 to 15 inches thick)
Btk1--26 to 40 inches; reddish brown (5YR 5/4) gravelly sandy loam, reddish brown (5YR 4/4) moist; weak medium subangular blocky structure; very hard, friable, slightly sticky and slightly plastic; common fine roots; common fine tubular pores; few thin clay films on faces of peds; 15 percent pebbles; slightly effervescent; few thin lime accumulations in pores; moderately alkaline (pH 8.0); clear wavy boundary. (10 to 12 inches thick)
Btk2--40 to 60 inches; light brown (7.5YR 6/4) gravelly sandy loam, reddish brown (5YR 4/4) moist; weak subangular blocky structure; very hard, friable, slightly sticky and plastic; few fine roots; few fine tubular pores; common thin clay films on faces of peds; 20 percent pebbles; strongly effervescent; common fine lime accumulations in pores and in filaments; moderately alkaline (pH 8.0).
TYPE LOCATION: Santa Cruz County, Arizona, 660 feet west of east 1/4 corner of sec. 23, T. 20 S., R. 12 E., 0.3 miles west of range house.
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: 59 to 72 degrees F.
Organic matter: Less than 1 percent
Rock fragments: Averages 5 to 35 percent in the particle-size control section.
Depth to argillic horizon: 10 to 30 inches; ranges from 20 to 40 or more inches in thickness.
Carbonates: Calcium carbonate equivalent less than 5 percent; secondary lime begins at depths of 10 to 30 inches. Many pedons are noneffervescent.
A horizon
Hue: 10YR, 7.5YR, or 5YR
Value: 4, 5, or 6 dry, 3 or 4 moist
Chroma: 3 or 4 dry and moist
Texture: Sandy loam, gravelly sandy loam
B horizon
Hue: 7.5YR, 5YR, or 2.5YR
Value: 4, 5, or 6 dry, 3, 4, or 5 moist
Chroma: 3, 4, or 6 dry and moist
Texture: Sandy loam, sandy clay loam (averages less than 18 percent clay in the particle-control section
Some pedons are underlain by a buried soil at 40 to 60 inches.
COMPETING SERIES: These are the Goldivide (CA), Helendale (CA), Searchlight (NV) and Tray (CA) series. Goldivide soils receive less rainfall and are moist for less than 20 days cumulative in some part of the moisture control section between July and October. Helendale soils have hues of 10YR or yellower and are noneffervescent above 40 inches. Searchlight soils contain more than 5 percent calcium carbonate equivalent. Tray soils are moderately well drained.
GEOGRAPHIC SETTING: Sonoita soils are on fan terraces and hillslopes. Slopes are 0 to 20 percent. The soils formed in stratified fan or hillslope alluvium derived from granitic rock and minor areas of rhyolite. Elevations range from 2000 to 5500 feet. The climate is warm, semiarid continental. The average annual precipitation is 9 to 13 inches. About one half falls as thundershowers in July, August and early September. The remainder occurs as gentle rain and light snowfall in the late fall and winter. The mean annual temperature is 57 to 70 degrees F. The frost-free period is 180 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Anthony, Arizo, Mohave, Pajarito, and Tres Hermanos soils. Anthony and Arizo soils are coarse- loamy and sandy-skeletal respectively. Mohave and Tres Hermanos soils are fine-loamy. Pajarito soils are adjacent, and have a cambic horizon.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; medium to slow runoff; moderately rapid permeability.
USE AND VEGETATION: Used for irrigated cropland, grazing, wildlife habitat and urban development. Native vegetation is paloverde, cholla, Arizona cottontop, threeawns, Rothrock grama, and annual grasses and forbs.
DISTRIBUTION AND EXTENT: Southeastern Arizona and Southwestern New Mexico. MLRAs 40, 41, & 42.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Santa Cruz County (Nogales area), Arizona, 1930.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 2 inches (A horizons)
Argillic horizon - The zone from about 17 inches to 60 inches or more (Bt & Btk horizons)
Secondary carbonates - The zone from about 26 inches to 60 inches or more (Btk horizons)
In 1992 questions were raised about the concept and classification of this series. A note in the series case file reads "4-17-92 Sonoita Do not use this series. Appears to be within the Sahuarita concept. The Santa Cruz soil survey has this soil in a 12-16" p.z. range site. The classification is quest. The 17 to 26" layer appears to be Bw cambic and not argillic. The lower subsoil is buried. PDC."