LOCATION LAJITAS            TX+AZ
Established Series
Rev. CCC/CEM
08/2009

LAJITAS SERIES


The Lajitas series consists of very shallow and shallow, well drained, moderately rapid over very slowly permeable bedrock. The soils developed in residuum and colluvium from slightly fractured volcanic bedrock. These soils are on hills and mountains. Slopes range from 5 to 60 percent. The mean annual precipitation is about 11 inches and the mean annual air temperature is about 67 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, nonacid, thermic Lithic Torriorthents

TYPICAL PEDON: Lajitas extremely cobbly loam--rangeland. (Colors are for dry soil unless otherwise noted.)

A1--0 to 1 inch; yellowish brown (10YR 5/4) extremely cobbly loam, dark yellowish brown (10YR 4/4) moist; weak thick platy structure; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; common very fine vesicular pores; 65 percent scoria cobbles and 15 percent gravel; noncalcareous; slightly alkaline; clear smooth boundary. (1 to 3 inches thick)

A2--1 to 4 inches; yellowish brown (10YR 5/4) extremely cobbly loam, dark yellowish brown (10YR 4/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; 70 percent cobbles; noncalcareous; slightly alkaline; abrupt irregular boundary. (3 to 20 inches thick)

R--4 inches; basalt scoria with common coarse Fe-MN stains on rock.

TYPE LOCATION: Pima County, Arizona; about 1,050 feet north and 1,710 feet west of the southeast corner of section 15, Township 14 S, and Range 13 E. Latitude: 32 degrees, 12 minutes 35 seconds N; Longitude: 111 degrees 0 minutes 0 seconds W.

RANGE IN CHARACTERISTICS:

Soil moisture: Intermittently moist in some part of the soil moisture control section during July-September and typic aridic soil moisture regime.

Depth to bedrock: 4 to 20 inches

Reaction: neutral to moderately alkaline

A horizons
Hue: 5YR, 7.5YR, 10YR
Value: 3 to 6, dry or moist
Chroma: 2 to 4, dry or moist
Texture: fine sandy loam, loam, sandy loam
Clay content: 5 to 27 percent
Rock fragments: 35 to 85 percent gravel, cobble, and stones
Some pedons have coatings of calcium carbonate on the surfaces of the fractures in the bedrock

COMPETING SERIES: These are the Cellar (AZ) and Nipton (NV) series. Cellar soils contain granite fragments, have a lithic contact with granite, and generally have B or C horizons. Nipton soils are moist in some part of the soil moisture control section for less than 20 days cumulative between July and September.

GEOGRAPHIC SETTING: Lajitas soils are on hills and mountains and formed from slope alluvium, colluvium and residuum weathered from basalt, andesite and other volcanic rocks. Slopes are from 5 to 60 percent. Mean annual precipitation is 10 to 12 inches. Mean annual air temperature is 64 to 70 degrees F. Frost-free period is 220 to 280 days, and elevation is 2,000 to 4,500 feet.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lehmans, Delthorny, and Bosa soils. Lehmans and Bosa soils have argillics. Delthorny soils have a petrocalcic horizon.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate to moderately rapid. Runoff is very high.

USE AND VEGETATION: Used mostly for livestock grazing. Vegetation consists of tanglehead, ocotillo, creosotebush, pricklypear, bush muhly, jojoba, paloverde, white brittle bush, and triangle bursage.

DISTRIBUTION AND EXTENT: Southern Arizona. This soil occurs in LRR-D, MLRAs 40 and 41. The series is of moderate extent.

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

SERIES ESTABLISHED: Brewster County, Texas; 1982.

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

Ochric epipedon - 0 to 1 inches (A horizon)

Lithic contact - the boundary with hard rock at 4 inches (R horizon)

Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Tenth Edition, 2006.

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

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

Type location was moved in July 2009. A temperature study in West Texas was completed and the original type location located in Big Bend National Park was determined to have a hyperthermic temperature regime. The original pedon was correlated to Studybutte. The type location was moved to AZ669 Pima County, AZ, Eastern Part to keep the series concept in the thermic temperature regime consistent with the original concept. The range in characteristics was slightly adjusted to reflect the correlated data from AZ661, AZ669, AZ675, and AZ703. CEM


National Cooperative Soil Survey
U.S.A.