LOCATION BOLUDO                  TX

Established Series
Rev. LEL/JLR/ACT
10/2012

BOLUDO SERIES

The Boludo series consists of soils that are very shallow and shallow to a petrocalcic horizon, and hard ignimbrite (welded tuff) bedrock. They are well drained, moderately permeable soils over a very slowly permeable petrocalcic horizon. These undulating soils formed in residuum weathered from the Mitchell Mesa Ignimbrite. They are on summits and crests of bedrock-capped mesas. Slopes range from 1 to 8 percent. The mean annual precipitation is about 12 inches and the mean annual air temperature is about 66 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Calcic Lithic Petrocalcids

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

A--0 to 4 inches; grayish brown (10YR 5/2) very gravelly clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky parting to moderate fine and medium granular structure; hard, firm; many very fine and fine roots throughout; 20 percent subrounded detached caliche pebbles, and 20 percent subrounded detached caliche cobbles; violently effervescent; moderately alkaline; clear smooth boundary (3 to 9 inches thick).

Bk--4 to 11 inches; brown (10YR 4/3) very gravelly clay loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure parting to moderate fine and medium granular; hard, firm; many very fine and fine roots throughout; many prominent continuous white (10YR 8/1) calcium carbonate coatings on rock fragments; 25 percent subrounded detached caliche gravel, 20 percent subrounded detached caliche cobbles, and 5 percent subrounded ignimbrite gravel; violently effervescent; moderately alkaline; abrupt smooth boundary (4 to 9 inches thick).

Bkkm--11 to 17 inches; strongly cemented caliche with indurated laminar cap 1 to 5 mm thick, violently effervescent; abrupt smooth boundary (3 to 7 inches thick).

R--17 to 80 inches; unweathered ignimbrite bedrock, moist; indurated; noneffervescent.

TYPE LOCATION: Brewster County, Texas; from the junction of U.S. Highways 90 and 67 in Marfa, 7.2 miles south-southwest on U.S. Highway 67 to junction with FM 169, 24.4 miles south on FM 169 to Plata, 6.2 miles south on Casa Piedra Road to intersection, 3.3 miles south and southeast on county road to intersection, 9.5 miles southeast and south on county road, 0.75 mile east-northeast on ranch road to Bennett Ranch headquarters, 3.45 miles east-northeast on ranch road climbing dipslope of Bandera Mesa, 0.2 mile southeast to water storage tank, 200 feet southwest in rangeland. (Latitude: 29 degrees, 37 minutes, 45 seconds North; Longitude: 103 degrees, 46 minutes, 46 seconds West; NAD 1927). Bandera Mesa North USGS 7.5 minute quadrangle.

RANGE IN CHARACTERISTICS:

Depth to a petrocalcic horizon: 7 to 18 inches

Depth to a lithic contact: 10 to 20 inches

Clay content PSCS: 20 to 35 percent

Rock fragments: 35 to 80 percent (Ignimbrite and detached caliche)

Mean annual soil temperature: 66 to 70 degrees F.

Soil Moisture: dry in all parts for less than three fourths of the cumulative days per year when the soil temperature at a depth of 50 cm from the soil surface is 5 degrees centigrade or higher. The soils occur in ustic aridic soil moisture regime.

A horizon
Hue: 7.5YR, 10YR
Value: 3 to 5, dry or moist
Chroma: 2 or 3, dry or moist
Texture: loam, clay loam
Rock fragments: 35 to 80 percent (Ignimbrite and detached caliche)
Reaction: slightly alkaline to moderately alkaline

Bk horizon
Hue: 7.5YR, 10YR
Value: 3 to 5, dry or moist
Chroma: 2 to 4, dry or moist
Texture: loam, clay loam
Rock fragments: Ignimbrite and detached caliche fragments range from 45 to 80 percent
Calcium carbonate equivalent: 20 to 40 percent
Reaction: moderately alkaline

Bkkm horizon
It is strongly or very strongly cemented caliche. Most pedons have an indurated laminar cap 1 to 5 mm thick.

R layer
It is indurated, noncalcareous, unweathered Mitchell Mesa Ignimbrite.

COMPETING SERIES: These are the Delthorny (AZ) and Manzanillo (TX) series. Delthorny soils have less than 18 percent clay and are in the typic aridic soil moisture regime. Manzanillo soils have 10 to 25 percent clay in the particle-size control section and formed over fanglomerate on fan remnants.

GEOGRAPHIC SETTING: Boludo soils are on bedrock-capped mesas. Slopes range from 1 to 8 percent. These soils formed in residuum weathered from the Mitchell Mesa Ignimbrite (welded tuff). Mean annual precipitation ranges from 10 to 15 inches, with most occurring from July through September. Mean annual air temperature ranges from 62 to 68 degrees F. Frost free period ranges from 210 to 260 days. Elevation ranges from 3,500 to 5,000 feet.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Decoty, Ohtwo, Sauceda, and Reduff series. None of these soils have a petrocalcic horizon. Decoty soils have a calcic horizon and are similar positions. Ohtwo soils are deep soils that are on lower steep to very steep colluvial scarps below the Mitchell Mesa Ignimbrite. They are on lower hills and scarps. Sauceda soils are very shallow and shallow to Mitchell Mesa Ignimbrite and are on more sloping areas near incised drainageways. Reduff soils are very shallow and shallow to tuffaceous bedrock of the Duff and Pruett Formations.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate in the surface layer and slow or very slow in the petrocalcic horizon and welded tuff bedrock. Runoff is medium on 1 to 3 percent slopes, high on 3 to 5 percent slopes, and very high on 5 to 8 percent slopes.

USE AND VEGETATION: This soil is used for livestock grazing. Woody species consist of mesquite, lechuguilla, creosotebush, prickly pear, redberry juniper, mariola, sacahuista, and narrowleaf forsteria. Grasses include black grama, sideoats grama, blue grama, threeawn, fluffgrass, tobosa, and plains bristlegrass.

DISTRIBUTION AND EXTENT: West Texas. MLRA 42. The soil is moderately extensive.

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

SERIES ESTABLISHED: Brewster County, Texas, 1997. The name is taken from Boludo Mountain in eastern Presidio County, Texas.

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

Ochric epipedon - The zone from 0 to 4 inches (A horizon)

Calcic horizon - The zone from 4 to 11 inches (Bk horizon)

Petrocalcic horizon - The zone from 11 to 17 inches (Bkm horizon)

Lithic contact - The boundary at 17 inches (R layer)

The soil meets all requirements for a mollic epipedon except some part of the epipedon is moist for less than 3 cumulative months in 8 out of 10 years.

Superactive cation exchange activity class - CEC to percent clay ratio is 0.60 or greater. This is assumed from the abundant zeolitic minerals in the Mitchell Mesa Ignimbrite, and from laboratory data from similar soils from Presidio County, Texas.

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

Update and revisions for Recorrelation of Brewster County, TX, Main Part, 2/7/08, CEM.

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

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National Cooperative Soil Survey
U.S.A.