LOCATION WILMAC NMEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, mesic Aridic Haplustalfs
TYPICAL PEDON: Wilmac loam, on a north facing, convex, 3 percent slope in rangeland at an elevation of 7,470 feet. (Colors are for dry soil unless otherwise noted.) When described on June 6, 1990 the soil was slightly moist from 0 to 38 inches.
A--0 to 3 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; soft, very friable, slightly sticky and slightly plastic; common very fine and fine roots; slightly effervescent, slightly alkaline (pH 7.6); clear smooth boundary. (2 to 6 inches thick)
Bt--3 to 16 inches; brown (10YR 5/3) clay loam, dark grayish brown (10YR 4/2) moist; moderate fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine, fine, and medium roots; common very fine tubular pores; common distinct clay films on faces of peds; strongly effervescent, slightly alkaline (pH 7.8); clear smooth boundary. (10 to 20 inches thick)
Btk--16 to 38 inches; light brownish gray (10YR 6/2) clay loam, brown (10YR 5/3) moist; moderate fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few very fine, fine and medium roots; common very fine tubular pores; common distinct clay films on faces of peds; common fine segregated carbonate filaments, strongly effervescent; 3 percent subangular shale gravels; moderately alkaline (pH 8.2); clear smooth boundary.
Cr--38 inches; soft shale; strongly effervescent
TYPE LOCATION: Rio Arriba County, New Mexico, Jicarilla Apache Indian Reservation; about 1 mile northwest of the town of Brazos; 1530 feet east, 2250 feet south of the NW corner, Sec. 36, T. 30 N., R. 3 E.; Brazos USGS quad; lat. 36 degrees 46 minutes 38 seconds N, long. 106 degrees 34 minutes 23 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. (Ustic moisture bordering on aridic.)
Mean annual soil temperature: 45 to 52 degrees F
Mean summer soil temperature: 55 to 65 degrees F
Depth to paralithic contact: 20 to 40 inches
Depth to secondary calcium carbonate: 9 to 23 inches
Particle-size control section (weighted average)
Clay content: 35 to 45 percent
Sand content: 20 to 50 percent
Rock fragments: 0 to 5 percent
A horizon
Value: 4 to 5 dry 3 to 4 moist
Chroma: 2 or 3
Clay content: 15 to 25 percent
Rock fragments: 0 to 5 percent
Content: 0 to 5 percent
Size: gravel
Kind: subrounded siltstone
Content: 0 to 5 percent
Size: cobble
Kind: rounded metamorphic (old riverwash)
Reaction: neutral to slightly alkaline
Bt horizon:
Value: 4 to 6
Chroma: 2 to 4
Texture: clay loam or clay
Clay content: 35 to 45 percent
Rock fragments: 0 to 5
Size: pebbles
Kind: subrounded shale and siltstone
Calcium carbonate equivalent: 0 to 5 percent
Reaction: neutral to slightly alkaline
Btk horizon:
Value: 4 to 7
Chroma: 2 or 3
Texture: clay loam or clay
Clay content: 35 to 45 percent
Rock fragments: 0 to 5 percent
Size: gravel
Kind: subangular shale and siltstone
Calcium carbonate equivalent: 0 to 10 percent
EC (mmhos/cm): 0 to 2
Gypsum: 0 to 5 percent
SAR: 0 to 5
Reaction: slightly to moderately alkaline
COMPETING SERIES: These are the Hosta, Prater, and Tinian series. Hosta and Prater soils are very deep. Tinian soils are overlying hard sandstone bedrock.
GEOGRAPHIC SETTING:
Parent material: alluvium and residuum derived from Mancos shale
Landform: shale hills
Slopes: 1 to 10 percent
Elevation: 6,900 to 7,700 feet
Mean annual temperature: 45 to 48 degrees F
Mean annual precipitation: 14 to 17 inches
Precipitation pattern: Precipitation falls mostly during the months of November through March and July through October. June is the driest month. Total snowfall averages about 3 to 4 feet with snowmelt lasting into April.
Frost-free period: 90 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hosta, Menefee, and Millpaw series. The Hosta and Millpaw soils are very deep and are in valleys, swales and drainageways. The Menefee soils are shallow and are on backslopes and ridges.
DRAINAGE AND PERMEABILITY: Well drained, medium runoff, slow permeability.
USE AND VEGETATION: The major uses are livestock grazing. The native plant community is western wheatgrass, blue grama, galleta, Rocky mountain juniper.
DISTRIBUTION AND EXTENT: Northwestern New Mexico; MLRA 36; moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Rio Arriba County, New Mexico, Jicarilla Apache Area, Parts of Rio Arriba and Sandoval Counties Soil Survey. The name Wilmac is coined.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Particle-size control section: The zone from 3 to 23 inches. (Bt, Btk horizons)
Ochric epipedon: The zone from 0 to 3 inches. (A horizon)
Argillic horizon: The zone from 3 to 38 inches. (Bt, Btk horizons)
Paralithic contact: The contact with shale at 38 inches. (Cr horizon)
Other features: carbonate, gypsum and pH increase with proximity to shale.
The assignment of the cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
Taxonomic Version: Second Edition, 1999
ADDITIONAL DATA: Lincoln Lab characterization sample taken within a Wilmac mapunit S92NM-039-003.