LOCATION COSTAVAR                AZ+TX

Established Series
Rev. CRP/DWD/PDC
10/2012

COSTAVAR SERIES

The Costavar series consists of very shallow and shallow to unweathered bedrock, well drained soils that formed in colluvium and residuum from volcanic rock such as dacitic breccia, basalt and rhyolite. Costavar soils are on hills and mountains. Slopes range from 30 to 75 percent. The mean annual precipitation is about 20 inches and the mean annual air temperature is about 59 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Aridic Lithic Argiustolls

TYPICAL PEDON: Costavar very gravelly sandy clay loam - recreation and wildlife habitat (colors are for dry soil unless otherwise noted).

A1--0 to 2 inches; brown (7.5YR 5/2) very gravelly sandy clay loam, very dark brown (7.5YR 2.5/3) moist; weak thick platy structure parting to moderate fine granular; slightly hard, very friable, slightly sticky and slightly plastic; few very fine roots; common very fine irregular pores; 40 percent gravel, 5 percent cobble; slightly effervescent; moderately alkaline (pH 8.2); abrupt wavy boundary.

A2--2 to 6 inches; brown (7.5YR 5/2) very gravelly sandy clay loam, very dark brown (7.5YR 2.5/3) moist; moderate fine subangular blocky structure parting to moderate fine granular; slightly hard, friable, slightly sticky and slightly plastic; common very fine and few fine roots; common very fine irregular and few fine tubular pores; 35 percent gravel, 5 percent cobble; strongly effervescent; moderately alkaline (pH 8.2); clear smooth boundary (combined thickness of the A horizons is 5 to 8 inches).

Bt--6 to 15 inches; reddish gray (5YR 5/2) very gravelly sandy clay loam, dark reddish brown (5YR 3/3) moist; strong very fine and fine subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine, fine, medium, and coarse roots; common very fine irregular and few fine and medium tubular pores; common faint, few distinct clay films on faces of peds and in pores; 45 percent gravel, 5 percent cobble; strongly effervescent; moderately alkaline (pH 8.2); abrupt irregular boundary (8 to 12 inches thick).

R--15 inches; hard, dacitic breccia with few very fine fractures between clastic rocks and tuffaceous matrix; fractures are fine enough to generally exclude roots.

TYPE LOCATION: Cochise County, Arizona; located at a latitude of 31 degrees, 20 minutes, 49 seconds North and longitude of 110 degrees, 16 minutes, 51 seconds West.

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. Aridic ustic soil moisture regime

Soil temperature: 59 to 64 degrees F.

Rock fragments: 35 to 80 percent dominated by gravel

Clay content: 20 to 35 percent

Organic matter: 1 to 3 percent

Calcium carbonate equivalent: 1 to 10 percent

Depth to unweathered bedrock: 6 to 20 inches

Some pedons have 1 to 3 inches of paralithic materials over the unweathered bedrock

A horizons
Hue: 7.5YR, 10YR
Value: 3 to 5 dry, 2 toh 3 moist
Chroma: 2 or 3, dry or moist
Texture: loam, sandy loam, sandy clay loam

Bt horizon
Hue: 5YR, 7.5YR, 10YR
Value: 3 to 6 dry, 2 to 4 moist
Chroma: 2 to 4, dry or moist
Texture: loam, clay loam, sandy clay loam

COMPETING SERIES: These are the Atascosa (I-AZ), Guaynaka (I-AZ), Silktassel (I-NM) and Woodcutter (AZ) series. Woodcutter soils are moderately acid to neutral. Atascosa, Guaynaka, and Silktassel soils are inactive.

GEOGRAPHIC SETTING: Costavar soils are on hills and mountains at elevations of 4,500 to 6,900 feet. Slopes range from 30 to 75 percent. These soils formed in colluvium and residuum from volcanic rock such as dacitic breccia, basalt and rhyolite. The mean annual precipitation is 15 to 23 inches and occurs as thunderstorms during July to September and as gentle rains during December to February. The mean annual air temperature is 57 to 62 degrees F. The frost-free period is 160 to 220 days

GEOGRAPHICALLY ASSOCIATED SOILS: This is the competing Guaynaka soils.

DRAINAGE AND PERMEABILITY: Well drained; rapid or very rapid runoff; moderate permeability.

USE AND VEGETATION: Used for livestock grazing, recreation and wildlife habitat. Vegetation includes sideoats grama, birchleaf mountain mahogany, bullgrass, pinyon pine, alligator juniper.

DISTRIBUTION AND EXTENT: Southeast Arizona and West Texas. Costavar soils are of minor extent. MLRAs 41 and 42.

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

SERIES ESTABLISHED: Cochise County, Arizona. Soil survey of Coronado National Memorial; 1996.

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

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

Argillic horizon - the zone from 6 to 15 inches (Bt horizon)

Lithic contact - the boundary at 15 inches (R horizon)

Classification changed to an Aridic Lithic subgroup in 2006. This change was made to be consistent with the moisture regime.

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

Updated competing series section 3/18/08, CEM

Revised for the correlation of Presidio County, Texas ; Oct, 2012, WWJ

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National Cooperative Soil Survey
U.S.A.