LOCATION NAHDA AZ

Established Series
Rev. CCC/DJB
04/2011

NAHDA SERIES

The Nahda series consists of moderately deep to hardpan, well drained soils formed in fan alluvium derived dominantly from acid igneous and metamorphic rock. Nahda soils are on erosional fan terraces with slopes of 1 to 25 percent. The mean annual precipitation is about 11 inches. The mean annual air temperature is about 68 degrees F.

TAXONOMIC CLASS: Clayey-skeletal, mixed, superactive, thermic Argic Petrocalcids

TYPICAL PEDON: Nahda extremely gravelly sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.)

E--0 to 2 inches; light brown (7.5YR 6/4) extremely gravelly sandy loam, brown (7.5YR 4/4) moist; weak medium and coarse platy structure; soft, very friable, nonsticky and nonplastic; common to many very fine and fine roots throughout; common to many very fine and fine vesicular pores; 50 percent gravel, 10 percent cobble; noneffervescent; slightly acid (pH 6.3); abrupt smooth boundary. (1 to 3 inches thick)

Bt--2 to 12 inches; yellowish red (5YR 5/6) extremely gravelly sandy clay, yellowish red (5YR 4/6) moist; moderate very fine and fine subangular blocky structure; slightly hard, friable, sticky and plastic; common to many very fine and fine and few to common medium roots throughout; few to common very fine and fine interstitial and tubular pores; many continuous faint red (2.5YR 4/6) clay films on faces of peds and in pores; common continuous faint clay films on rock fragments; 60 percent gravel, 10 percent cobble; noneffervescent; neutral (pH 6.9); clear wavy boundary. (8 to 15 inches thick)

Btk1--12 to 23 inches; red (2.5YR 5/8) extremely gravelly sandy clay, red (2.5YR 4/8) moist; moderate very fine and fine subangular blocky structure; slightly hard, friable, very weakly cemented, sticky and plastic; common to many fine and medium roots matted around stones; few to common very fine and fine interstitial and tubular pores; common faint red (2.5YR 4/6) clay films on faces of peds and in pores; few very fine and fine threads and soft masses of lime; 60 percent gravel, 10 percent cobble; slightly effervescent; slightly alkaline (pH 7.8); gradual wavy boundary.

Btk2--23 to 36 inches; red (2.5YR 5/8) extremely gravelly sandy clay, red (2.5YR 4/8) moist; moderate very fine and fine subangular blocky structure; slightly hard, friable, very weakly cemented, sticky and plastic; common to many fine and medium roots matted around stones; few to common very fine and fine interstitial and tubular pores; common distinct manganese or iron-manganese coats throughout; common faint red (2.5YR 4/6) clay films on faces of peds and in pores; few very fine and fine threads and soft masses of lime; 70 percent gravel, 10 percent cobble; strongly effervescent; slightly alkaline (pH 7.8); abrupt wavy boundary. (Combined thickness of the Btk horizons is 9 to 24 inches)

Bkkm--36 to 60 inches; pinkish white (7.5YR 8/2) strongly cemented petrocalcic horizon, pink (7.5YR 7/4) moist; massive; extremely hard; few very fine and fine roots in fractures; violently effervescent.

TYPE LOCATION: Pima County, Arizona; 350 feet east and 1000 feet north of the southwest corner of section 26, T. 14 S., R. 6 E.

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.

Soil temperature - 66 to 72 degrees F.

Depth to Hardpan - 20 to 40 inches

Organic Matter - 0.1 to 0.5 percent in the upper 16 inches

Calcium carbonate - None in the upper 10 inches. Increases to 15-75 percent calcium carbonate equivalent above 40 inches

Rock Fragments - 35 to 85 percent by volume gravel and cobble

average percent clay in the control section: 35 to 60 percent

A horizon
Hue: 5YR, 7.5YR
Value: 4, 5, 6, or 7 dry, 3, 4, or 5 moist
Chroma: 3 through 6, dry or moist
Reaction: slightly acid through slightly alkaline

Bt horizon
Hue: 2.5YR, 5YR
Value: 3 through 6 dry
Chroma: 3 through 8, dry or moist
Texture: clay, sandy clay, sandy clay loam, clay loam
Reaction: neutral through moderately alkaline

Btk horizon
Hue: 2.5YR, 5YR
Value: 3 to 6 dry, 3 to 5 moist
Chroma: 4 through 8, dry or moist
Texture: sandy clay, sandy clay loam, clay, clay loam
Reaction: slightly or moderately alkaline

COMPETING SERIES: This is the Caracara (AZ) series. Caracara soils have conglomerate bedrock below the petrocalcic horizon.

GEOGRAPHIC SETTING: Nahda soils are on fan terraces. Slope is 1 to 45 percent. They formed in fan alluvium derived dominantly from igneous and metamorphic rock. Elevation ranges from 1,800 to 3,770 feet. The mean annual precipitation is 10 to 12 inches. The mean annual air temperature ranges from 64 to 70 degrees F. The frost-free period is 220 to 280 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Continental, Delnorte and Tubac series. The Continental and Tubac series are fine textured and lack petrocalcic horizons within 40 inches of the surface. The Delnorte series lacks an argillic horizon and is shallow to a petrocalcic horizon.

DRAINAGE AND PERMEABILITY: Well drained; medium runoff; slow permeability.

USE AND VEGETATION: Used mainly for livestock grazing and wildlife habitat. Vegetation is triangle bursage, paloverde, ironwood, saguaro, chainfruit cholla, cane cholla, prickly pear, bisnaga and ocotillo.

DISTRIBUTION AND EXTENT: Southern Arizona. This series is moderately extensive. MLRA 40.

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

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

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon - the zone from 0 to 2 inches (E horizon)

Argillic horizon - the zone from 2 to 36 inches (Bt, Btk1, Btk2 horizons)

Petrocalcic horizon - the zone from 36 to 60 inches (Bkm horizon)

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

Revised for the correlation of AZ661, 2/2009, WWJ

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

National Cooperative Soil Survey
U.S.A.