LOCATION AZTEC                   NV+NM

Established Series
Rev. ELS/RPZ/ET
04/2015

AZTEC SERIES

The Aztec series consists of very deep, well drained soils that formed in mixed alluvium with a large component of gypsum. The Aztec soils are on erosional fan remnants. Slopes are 2 to 30 percent. The mean annual precipitation is about 5 inches and the mean annual temperature is about 66 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, mixed, active, thermic Typic Calcigypsids

TYPICAL PEDON: Aztec very gravelly sandy loam-desert wildlife habitat. (Colors are for dry soil unless otherwise noted.)

A--0 to 2 inches; light yellowish brown (10YR 6/4) very gravelly sandy loam, dark yellowish brown (10YR 4/4) moist; weak very thick platy structure; soft, very friable, nonsticky and nonplastic; common very fine roots; common very fine vesicular pores; 55 percent pebbles, 4 percent cobbles; slightly effervescent; slightly alkaline (pH 7.8); abrupt wavy boundary. (l to 3 inches thick)

C--2 to l5 inches; light yellowish brown (10YR 6/4) extremely gravelly sandy loam, dark yellowish brown (10YR 4/4) moist; massive; soft, very friable, nonsticky and nonplastic; many very fine and few fine roots; 75 percent pebbles, 6 percent cobbles; slightly effervescent; moderately alkaline (pH 8.0); gradual wavy boundary. (5 to l5 inches thick)

Ck--l5 to 30 inches; light brown (7.5YR 6/4) very gravelly sandy loam, dark brown (7.5YR 4/4) moist; massive; soft, very friable, nonsticky and non- plastic; many very fine and few fine roots; 55 percent pebbles; few thin lime coatings on pebbles; strongly effervescent; slightly alkaline (pH 7.8); clear wavy boundary. (l0 to 24 inches thick)

Cyk--30 to 5l inches; light reddish brown (5YR 6/4) very gravelly sandy loam, reddish brown (5YR 4/4) moist; massive; slightly hard, very friable, nonsticky and nonplastic; common very fine and few medium roots; 60 percent pebbles; many distinct gypsum crystals and gypsum pendants on pebbles; some masses weakly cemented by gypsum; strongly effervescent; slightly alkaline (pH 7.8); clear wavy boundary. (l5 to 30 inches thick)

Cy--5l to 63 inches; light reddish brown (5YR 6/4) extremely gravelly loamy coarse sand, reddish brown (5YR 4/4) moist; massive; slightly hard, very friable, nonsticky and nonplastic; few fine and medium roots; 75 percent pebbles; many distinct gypsum crystals and thin gypsum pendants on pebbles; some masses weakly cemented by gypsum; slightly effervescent; slightly alkaline. (pH 7.8)

TYPE LOCATION: Clark County, Nevada; approximately 300 feet south of Highway 93, about 2,l00 feet west of the southeast corner of section l2 T. l3 S., R. 63 l/2 E.

RANGE IN CHARACTERISTICS:

Soil moisture: Usually dry. Moist for short periods throughout the moisture control section December through March. Moist above and periodically in upper part of moisture control section, 1 to 10 days cumulative, June through August. Soil temperature: 63 to 70 degrees F.

Control section
Texture of fine earth: Stratified, but averages sandy loam or fine sandy loam.
Percent clay: 3 to l5.
Rock fragments: 35 to 80 percent, mostly pebbles.
Depth to the gypsic horizon: l0 to 30 inches.
Reaction: Neutral through strongly alkaline.

A horizon
Hue: l0YR, 7.5YR or 5YR.
Value: 6 or 7 dry, 4 through 6 moist.
Chroma: 2 through 4.

C horizon
Hue: l0YR, 7.5YR or 5YR.
Value: 6 through 8 dry, 4 through 7 moist.
Chroma: l through 4.

Cyk horizon
Cementation: Weak cementation, continuous in some pedons.

Cy horizon
Other features: Weak, discontinuous cementation in some pedons.

COMPETING SERIES: This is the Arrolime series. Arrolime soils contain l8 to 35 percent clay and less than l5 percent fine through coarse sand in the fine earth fraction of the control section.

GEOGRAPHIC SETTING: Aztec soils are on erosional fan remnants. These soils formed in mixed alluvium with a large component of gypsum. Slopes are 7 to 30 percent. Elevations are l,600 to 5,400 feet. The climate is arid with hot dry summers and mild winters. The mean annual precipitation is 4 to l0 inches; mean annual temperature is 65 to 72 degrees F., and the frost-free season is l80 to 270 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arizo, Caliza, and Knob Hill series. Arizo and Caliza have sandy-skeletal control sections. Knob Hill soils have less than 35 percent rock fragments.

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

USE AND VEGETATION: Rangeland and wildlife habitat. The present vegetation is mainly creosotebush and white bursage.

DISTRIBUTION AND EXTENT: Southern Nevada and southern New Mexico, Nevada in MLRA 30. These soils are moderately extensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California

SERIES ESTABLISHED: Clark County, (Las Vegas and El dorado Valleys Area) Nevada. l964.

REMARKS: The type location has been moved to the present location to better represent the present series concept. Aztec soils were formerly classified as loamy-skeletal, mixed, thermic Typic Haplogypsids. The classification was revised in March of 2003 recognizing the calcic horizon above the gypsic and adding the CEC activity class using the second edition to Soil Taxonomy. Competing series were not checked at that time. -ET

Responsibility for this series was transferred from Davis to Phoenix 4/2015. The last revision to the series was 3/2003. ET

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National Cooperative Soil Survey
U.S.A.