LOCATION LEYVA                   TX

Established Series
Rev. DWM/JG
07/2012

LEYVA SERIES

The Leyva series consists of very shallow and shallow, well drained soils that formed in colluvium and residuum weathered from rhyolitic bedrock. Leyva soils are on mountainsides and hill slopes. Slope ranges from 1 to 60 percent. The mean annual precipitation is about 13 inches and the mean annual air temperature is about 65 degrees F.

TAXONOMIC CLASS: Clayey-skeletal, mixed, superactive, thermic Lithic Ustic Haplargids

TYPICAL PEDON: Leyva very gravelly loam - rangeland. (Colors are for dry soil unless otherwise stated.)

A--0 to 4 inches; brown (7.5YR 4/2) very gravelly loam, dark brown (7.5YR 3/2) moist; 26 percent silicate clay; moderate fine subangular blocky structure parting to moderate fine granular structure; friable, slightly hard; common fine and very fine roots throughout; 35 percent angular igneous gravel, 10 percent angular igneous cobbles; noneffervescent; neutral(pH 7.3); clear smooth boundary. (2 to 7 inches thick)

Bt--4 to 15 inches; brown (7.5YR 4/3) very gravelly clay loam, dark brown (7.5YR 3/3) moist; 38 percent silicate clay; moderate medium subangular blocky structure parting to moderate fine subangular blocky structure; friable, moderately hard; common fine and very fine roots throughout; few continuous distinct clay films on all faces of peds and common continuous distinct clay films on rock fragments; 45 percent angular igneous gravel, 10 percent angular igneous cobbles; noneffervescent; neutral (pH 7.1); very abrupt smooth boundary. (4 to 14 inches thick)

R--15 inches; very strongly cemented rhyolitic bedrock, noneffervescent, neutral.

TYPE LOCATION: Brewster County, Texas; from junction of US Highway 385 and State Highway 118, 4.8 miles west on State Highway 118, 0.1 miles north in rangeland; The Basin, TEXAS USGS 7.5 minute topographic quadrangle; NAD83. UTM coordinates: 667516 meters E, 3248102 meters N, Zone 13. Located at latitude of 29 degrees, 21 minutes, 3.30 seconds North and a longitude of 103 degrees, 16 minutes, 27.83 seconds West.

RANGE IN CHARACTERISTICS:

Soil Moisture: Ustic aridic

Soil Temperature: 64 to 70 degrees F.

Depth to bedrock: 7 to 18 inches

Particle-size control section (weighted average)
Clay content: 35 to 50 percent
Calcium carbonate equivalent: 0 to 5 percent
Rock fragments: 40 to 80 percent

A horizon
Hue: 5YR, 7.5YR
Value: 3 to 5 dry, 2.5 to 4 moist
Chroma: 2 to 4, dry or moist
Texture: sandy loam, loam, sandy clay loam, clay loam
Clay content: 17 to 40 percent
Rock fragments: 20 to 70 percent
Reaction class: neutral

Bt horizon
Hue: 5YR, 7.5YR
Value: 3 to 5 dry, 2.5 to 4 moist
Chroma: 2 to 6, dry or moist
Texture: clay loam, clay
Clay content: 35 to 50 percent
Rock fragments: 45 to 80 percent
Reaction: neutral

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING:
Leyva soils are on mountains and hill. They formed in colluvium and residuum from rhyolitic rock. Slope ranges from 1 to 60 percent. Elevation is from 2,400 to 5,500 feet. The mean annual mean annual air temperature is 62 to 67 degrees F. and the mean annual precipitation is 12 to 16 inches. They receive precipitation in all months. The driest period is November through April with peak rainfall occurring as high intensity rainfall during convectional afternoon thunderstorms from June through September. The frost-free period is 210 to 250 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lingua and Pantak soils.
Lingua and Pantak soils are loamy-skeletal and occur on similar landforms.

DRAINAGE AND PERMEABILITY: Well drained; Runoff is high on 10 to 20 percent slopes; and very high on slopes over 20 percent; moderately slow permeability.

USE AND VEGETATION: This soil is used mainly for livestock grazing and wildlife habitat. Woody plants include skeletonleaf goldeneye, lechuguilla, sotol, mariola, ocotillo, elbowbush, catclaw mimosa, and Torrey yucca. Grasses include black grama, sideoats grama, tanglehead, fluffgrass, bush muhly, Halls panicum, and spider threeawn.

DISTRIBUTION AND EXTENT: LRR D, MLRA 42-Southern Desertic Basins, Plains, and Mountains. The series is moderately extensive.

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

SERIES ESTABLISHED: Big Bend National Park, Brewster County, Texas; 2010. The name is taken from Leyva Canyon in Big Bend Ranch State Park.

REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 4 inches (A horizon)
The soil may meet all requirements for a mollic epipedon, except some part of the epipedon is moist for less than 90 days (cumulative) in normal years during times when the soil temperature at a depth of 20 inches is 41 degrees F.

Argillic horizon - the zone from 4 to 15 inches (Bt horizon)

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

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

Revised for the correlation of Hudspeth County, Texas (Main Part) and Culberson County, Texas (Main Part); July, 2012, NMS

ADDITIONAL DATA: Local lab analysis included calcium carbonate equivalent, electrical conductivity, particle-size analysis, pH, and sand fractions on 3 pedons from Big Bend National Park.

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National Cooperative Soil Survey
U.S.A.