LOCATION VALTO CO+NM
Established Series
Rev. JPP/TWH/KLS
03/2018
VALTO SERIES
The Valto series consists of shallow, well drained soils that formed in slope alluvium or colluvium derived mainly from sandstone. Valto soils are on mountain slopes, canyon sideslopes, ridges, hillslopes, and breaks. Slopes range from 3 to 65 percent. Mean annual precipitation is about 635 cm and the mean annual temperature is about 6.1 degrees C.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Lithic Haplustepts
TYPICAL PEDON: Valto very stony fine sandy loam, on a south facing, simple, 20 percent slope in ponderosa pine woodland at an elevation of 2,560 meters. (Colors are for dry soil unless otherwise noted.)
Oi--0 to 5 cm; forest litter of pine needles and leaves. (0 to 8 cm thick)
A--5 to 10 cm; dark reddish gray (5YR 4/2) very stony fine sandy loam, dark reddish brown (5YR 2/2) moist; weak medium platy structure parting to weak fine granular; soft, very friable, nonsticky and nonplastic; 20 percent stones, 30 percent cobbles, and 10 percent gravel; neutral (pH 7.0); abrupt smooth boundary. (3 to 10 cm thick)
Bw--10 to 36 cm; light reddish brown (5YR 6/3) very stony fine sandy loam, reddish brown (5YR 5/3) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; 20 percent stones, 30 percent cobbles, and 10 percent gravel; neutral (pH 7.0); clear smooth boundary. (13 to 48 cm thick)
R--36 cm; hard sandstone.
TYPE LOCATION: La Plata County, Colorado; about 8 kilometers north of Durango, Colorado; in Durango Hills subdivision about 1 kilometer on Sagebrush Trail from junction with Stagecoach Road; located about 610 meters east of the northwest corner of Sec. 7, T. 35 N., R. 8 W. Durango East USGS quad.; Lat. 37 degrees, 19 minutes, 26 seconds N., and Long. 107 degrees, 47 minutes, 18 seconds W., NAD 27.
RANGE IN CHARACTERISTICS: (depths given are measured from the mineral soil surface)
Mean annual soil temperature: 6.1 to 8.3 degrees C.
Mean annual summer soil temperature: 15.6 to 18.3 degrees C.
Depth to lithic contact: 15 to 51 cm to sandstone
Lithology of rock fragments: sandstone
Particle-size control section:
Clay content: 5 to 18 percent
Silt content: 5 to 50 percent
Sand content: 40 to 80 percent
Rock fragment content: 30 to 70 percent angular stones and cobbles, 5 to 20 percent gravel
A horizon
Hue: 2.5YR to 7.5YR
Value: 4 to 6 dry, 2 to 4 moist
Chroma: 2 to 4, dry and moist
Texture, fine earth fraction: fine sandy loam, sandy loam
Rock fragment content: 30 to 70 percent
Reaction (pH): 6.1 to 7.3
Bw horizon
Hue: 2.5YR to 7.5YR
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 2 to 4, dry and moist
Texture, fine earth fraction: fine sandy loam, sandy loam
Rock fragment content: 30 to 70 percent
Reaction (pH): 6.1 to 7.3
COMPETING SERIES:
Cinnadale (NM) - have greater than 50 percent silt in the Bw horizon
Cypher (NM) - have hues yellower than 7.5YR
Devilfence (MT) - have horizons of secondary carbonate accumulation
Deville (MT) - have rock fragments of shale
Kounter (MT) - have horizons of secondary carbonate accumulation; have paralithic contact above the lithic contact
Quaint (MT) - have horizons of secondary carbonate accumulation and hues redder than 7.5YR
Roegulch (MT) - have a paralithic contact above the lithic contact
Shamoom (MT) - have hues yellower than 7.5YR
Sharrott (MT) - have rock fragments of argillite or quartzite
Villareal (CO) - have rock fragments of andesite
GEOGRAPHIC SETTING:
Landform - mountain slopes, canyon sideslopes, hillslopes, ridges, and breaks.
Elevation - 2,130 to 3,050 meters
Slopes - 3 to 80 percent
Parent material - slope alluvium or colluvium derived mainly from sandstone, however some pedons formed in material derived from limestone or quartzite.
Mean annual air temperature - 4.4 to 7.8 degrees C.
Mean annual precipitation - 410 to 760 mm
Precipitation pattern - July and August are wettest months, May and June are driest months, however the soils are still moist from snowmelt.
Frost-free period - 75 to 115 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained, moderately high runoff, moderate or moderately rapid permeability.
USE AND VEGETATION: These soils are used for timber production, livestock grazing, and wildlife habitat. Native vegetation is ponderosa pine, Gambel oak, Arizona fescue, mountain muhly, Thurber's fescue, and bluegrasses, with some minor amounts of Rocky Mountain Douglas fir.
DISTRIBUTION AND EXTENT: Southwestern Colorado, northern New Mexico. LRR D, E; MLRA 36, 48A; moderate extent.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: La Plata County Area, Colorado, 1982. Series proposed in 1975. The name is modified from the name of a local reservoir.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Cambic horizon: 5 to 30 cm (Bw horizon)
Lithic contact: 36 cm to hard sandstone bedrock
Particle size control section: 5 to 36 cm (A and Bw horizons)
Valto soils have a frigid temperature regime and are in an ustic soil moisture regime with a typic subclass.
The 06/2002 revision changed the classification from Lithic Ustorthents to Lithic Haplustepts. This change meant that very shallow soils could no longer be included in the series (because the cambic horizon must extend deeper than 10 inches). Very shallow soils were determined to be of minor extent. This revision also restricted the moisture regime to typic ustic, and deleted Engelmann's spruce and white fir from the characteristic plant community.
The series concept needs to be narrowed further, particularly the climatic properties.
National Cooperative Soil Survey
U.S.A.