LOCATION LOMAPEDRO NMEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Pachic Argiustolls
TYPICAL PEDON: Lomapedro loam, on a northwest facing, planar, 5 percent slope in rangeland at an elevation of 8,400 feet. (Colors are for dry soil unless otherwise noted.) When described the soil was slightly moist from 30 to 52 inches.
A1--0 to 2 inches; dark grayish brown (10YR 4/2) loam, very dark brown (10YR 2/2) moist; weak fine platy structure 1/4 inch thick over weak fine granular; soft, very friable, slightly sticky and slightly plastic; many very fine roots; neutral (pH 6.6); clear smooth boundary. (1 to 8 inches thick)
A2--2 to 8 inches; very dark grayish brown (10YR 3/2) loam, black (10YR 2/1) moist; weak fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine roots; slightly acid (pH 6.4); clear smooth boundary. (4 to 8 inches thick)
A3--8 to 20 inches; brown (10YR 4/3) loam, very dark brown (10YR 2/2) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots; few very fine and fine irregular pores; 5 percent gravel and 5 percent cobbles; slightly acid (pH 6.4); clear smooth boundary. (12 to 24 inches thick)
Bt1--20 to 26 inches; brown (7.5YR 5/2) clay loam, dark brown (7.5YR 3/4) moist; moderate medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few distinct clay films on faces of peds; few fine and medium roots; common very fine and fine irregular pores; 5 percent gravel and 5 percent cobbles; slightly acid (pH 6.4); abrupt smooth boundary. (7 to 18 inches thick)
Bt2--26 to 37 inches; light brown (7.5YR 6/4) clay, dark reddish gray (5YR 4/2) moist; strong medium prismatic structure parting to strong medium subangular blocky; extremely hard, extremely firm, very sticky and very plastic; common prominent clay films on faces of peds; few fine and medium roots; few very fine and fine irregular pores; 5 percent gravel and 5 percent cobbles; slightly acid (6.4); clear smooth boundary. (2 to 11 inches thick)
Bt3--37 to 52 inches; brownish yellow (10YR 6/6) clay loam yellowish brown (10YR 5/4) moist, common medium distinct light gray (10YR 7/2) lithochromic mottles; moderate fine subangular blocky structure; very hard, very firm, moderately sticky and moderately plastic; common distinct clay films on faces of peds; few fine and medium roots; few very fine and fine irregular pores; 5 percent gravel and 5 percent cobbles; slightly alkaline (pH 7.4); abrupt smooth boundary. (8 to 23 inches thick)
Cr--52 inches; interbedded sandstone and shale.
TYPE LOCATION: Rio Arriba County, NM; about 2 miles east of Horse Lake; located in an unsurveyed area, about 2650 feet west, and 500 feet north of the SE corner, section 18, T. 30 N., R. 2 E.; Horse Lake USGS quad; lat. 36 degrees 52 minutes 17 seconds N. and long. 106 degrees 47 minutes 15 seconds W., NAD 27.
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is affected by precipitation that is evenly distributed throughout the year with the exception of a significant peak during July and August, and a significant decrease from April through June. June is the driest month. Typic ustic moisture regime.
Mean annual soil temperature: 42 to 45 degrees F
Mean summer soil temperature: 58 to 62 degrees F
Depth to paralithic contact: 40 to 60 inches to interbedded sandstone and shale
Depth to argillic horizon: 7 to 26 inches
Thickness of the mollic epipedon: 20 to 41 inches
Particle-size control section (weighted average):
Clay content: 36 to 48 percent
Sand content: 16 to 35 percent
Rock fragments:
Content: 0 to 15 percent
Size: stone, cobble, gravel
Kind: subrounded sandstone
A horizon:
Hue: 7.5YR or 10YR
Value: 2 to 5 dry, 2 or 3 moist
Chroma: 1 to 3
Reaction: neutral to slightly acid
Bt1 horizon:
Hue: 7.5YR to 10YR
Value: 4 to 5 dry, 2 to 3 moist
Chroma: 2 to 4
Texture: loam or clay loam
Reaction: neutral to slightly acid
Bt2 horizon:
Hue: 7.5YR to 10YR
Value: 5 to 6 dry, 4 to 5 moist
Chroma: 2 to 4
Texture: clay or clay loam
Reaction: neutral to slightly acid
Bt3 horizon:
Hue: 7.5YR to 10YR
Value: 4 to 6
Chroma: 2 to 4
Texture: clay or clay loam
Reaction: neutral to slightly alkaline
COMPETING SERIES: These are the Encicado, Gaines, Robolata, and Seeprid series. Encicado soils have a discontinuity with clayey-skeletal materials in the subsoil. . Gaines and Seeprid soils have hard bedrock at 40 to 60 inches. Robolata soils are very deep.
GEOGRAPHIC SETTING:
Parent material: slope alluvium over residuum derived from sandstone and shale
Landform: cuestas, mesas, and structural benches
Slopes: 1 to 15 percent
Elevation: 7000 to 8700 feet
Mean annual temperature: 42 to 45 degrees F
Mean annual precipitation: 16 to 20 inches
Precipitation pattern: Precipitation falls year round but peaks in July and August, and declines in spring. April, May, and June are the driest months. Total snowfall averages about 4 to 5 feet with snowmelt lasting through April.
Frost-free period: 80 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Stout, Suposo, and Zau series. The Stout soils are shallow and on ridges. Zau soils are moderately deep and on similar positions. The Suposo soils are very deep and are in swales.
DRAINAGE AND PERMEABILITY: Well drained, low to medium runoff, slow permeability.
USE AND VEGETATION: The major uses are livestock grazing and wildlife habitat. The native plant community is western wheatgrass, needleandthread, little bluestem, blue grama, prairie junegrass, scattered Gambel's oak, and ponderosa pine.
DISTRIBUTION AND EXTENT: Northern New Mexico, RM-2 subresource area, MLRA 36; small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Rio Arriba County, New Mexico, Jicarilla Area, Parts of Rio Arriba and Sandoval Counties Soil Survey, 2000. The name Lomapedro is taken from a local mesa name.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Particle-size control section: The zone from 20 to 40 inches. (Bt1, Bt2, Bt3 horizons)
Mollic epipedon: The zone from 0 to 20 inches. (A1, A2, A3 horizons)
Argillic horizon: The zone from 20 to 52 inches. (Bt1, Bt2, Bt3 horizons)
Paralithic contact: The contact with interbedded sandstone and shale at 52 inches. (top of Cr layer)
Taxonomic Version: Tenth Edition, Keys, 2006
ADDITIONAL DATA:
Texture by hydrometer analysis for horizons in the 0 to 37 inch zone, Intermountain Labs Inc., Farmington, NM.