LOCATION COMBATE                 AZ

Established Series
Rev. DJB/CEM/WAS
06/2011

COMBATE SERIES

The Combate series consists of very deep, somewhat excessively drained soils formed in fan alluvium from granite. Combate soils are on alluvial fans and flood plains and have slopes of 0 to 10 percent. The mean annual precipitation is about 14 inches. The mean annual air temperature is about 65 degrees F.

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, nonacid, thermic Ustic Torrifluvents

TYPICAL PEDON: Combate gravelly loamy coarse sand - rangeland. (Colors are for dry soil unless otherwise noted.)

A1--0 to 1 inch; brown (10YR 5/3) gravelly loamy coarse sand, dark brown (10YR 3/3) moist; weak very fine and fine granular structure; slightly hard, very friable, nonsticky and nonplastic; many very fine and fine and few medium roots; 30 percent gravel; noneffervescent; neutral (pH 6.6); clear smooth boundary.

A2--1 to 15 inches; dark grayish brown (10YR 4/2) gravelly loamy coarse sand, very dark brown (10YR 2/2) moist; weak very fine and fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine and few medium roots; 25 percent gravel; noneffervescent; neutral (pH 6.8); gradual wavy boundary. (Combined thickness of the A horizons is 5 to 20 inches)

C1--15 to 29 inches; brown (10YR 4/3) gravelly coarse sandy loam, very dark brown (10YR 2/2) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine and few medium roots; 30 percent gravel; noneffervescent; slightly acid (pH 6.5); gradual wavy boundary. (10 to 20 inches thick)

C2--29 to 60 inches; yellowish brown (10YR 5/4) very gravelly coarse sandy loam, dark yellowish brown (10YR 3/4) moist; massive; soft, very friable, nonsticky and nonplastic; many very fine and fine and few medium roots; 35 percent gravel; noneffervescent; neutral (pH 6.9).

TYPE LOCATION: Pima County, Arizona. Latitude of 31 degrees, 57 minutes, 40 seconds North and a longitude of 111 degrees, 33 minutes, 34 seconds West; about 1700 feet West and 1800 feet South of the Northwest corner of Section 8, T. 17 S., R. 8 E.

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. The epipedon is moist in some part less than 90 days (cumulative) when the soil temperature is above 41 degrees F. in 7 out of 10 years. Ustic aridic soil moisture regime.

Soil Temperature: 59 to 70 degrees F.

Rock fragments: averages less than 35 percent gravel

Calcium carbonate equivalent: 0 to 3 percent below 20 inches

Organic matter: 1 to 3 percent in the surface and more than .35 percent at a depth of 50 inches

A horizon
Hue: 10YR, 7.5YR
Value: 3 through 5 dry, 2 through 4 moist
Chroma: 1 through 4, dry or moist
Reaction: slightly acid or neutral

C horizons
Hue: 10YR, 7.5YR
Value: 3 through 5 dry, 2 through 4 moist
Chroma: 2 through 6, dry or moist
Reaction: slightly acid to moderately alkaline
Texture: sandy loam, coarse sandy loam, loamy sand, loamy fine sand, coarse sand, sand (less than 18 percent clay)

Some pedons have a buried paleosol in the lower substratum.

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING: Combate soils are on alluvial fans and flood plains. Slopes range from 0 to 10 percent, but are dominantly 1 to 5 percent. These soils formed in fan alluvium derived from gneiss and granite. Elevation ranges from 2,500 to 5,060 feet. The mean annual precipitation is 12 to 16 inches. The mean annual air temperature is 60 to 68 degrees F. The frost-free period is about 180 to 250 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Baboquivari, Romero, Oracle and Comoro soils. Baboquivari and Oracle soils have argillic horizons. Romero and Oracle soils are shallow to a paralithic contact. Comoro soils are calcareous and occur in bottom positions.

DRAINAGE AND PERMEABILITY: Somewhat excessively drained; slow runoff; moderately rapid permeability. Subject to rare sheet flooding in some areas.

USE AND VEGETATION: Used for livestock grazing and wildlife habitat. Vegetation includes Arizona cottontop, spike dropseed, sideoats grama, mesquite, Santa Rita three-awn, shrubby buckwheat and Rothrock grama.

DISTRIBUTION AND EXTENT: Southern Arizona. This series is of moderate extent. This soil occurs in LRR-D, MRLA 41.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona

SERIES ESTABLISHED: Pima County, Arizona; Soil survey of Tohono O'odham Nation, AZ, Parts of Maricopa, Pima and Pinal Counties; 1993.

REMARKS: Formerly part of the Comoro series. The original Comoro concept allowed for soils that were either calcareous or noncalcareous which crossed reaction classes. The presence or absence of carbonates in these soils was found to be associated with landform and position and easily separated.

Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon - the zone from 0 to 15 inches (A1, A2 horizons)

Entisol feature - the absence of diagnostic subsurface horizons

Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Eleventh Edition, 2010.

Revised for the correlation of AZ661, 12/2008, WWJ

Revised for the correlation of AZ675, 5/2009, WWJ

Revised for the correlation of Graham County, AZ, Southwestern Part; March, 2011, WWJ

---

National Cooperative Soil Survey
U.S.A.