LOCATION UMBARG COEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Cumulic Haplustolls
TYPICAL PEDON: Umbarg loam, on a southwest facing, simple, 3 percent slope in irrigated pasture at an elevation of 6,580 feet. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 7 inches; dark grayish brown (10YR 4/2) loam, very dark brown (10YR 2/2) moist; moderate medium subangular blocky structure parting to weak very fine subangular blocky; slightly hard, friable; slightly sticky and nonplastic; strongly effervescent; 5 percent pebbles; slightly alkaline (pH 7.4); clear smooth boundary. (5 to 10 inches thick)
A--7 to 17 inches; dark grayish brown (10YR 4/2) loam, very dark brown (10YR 2/2) moist; moderate medium subangular blocky structure parting to weak very fine subangular blocky; slightly hard, friable, slightly sticky and nonplastic; strongly effervescent; 5 percent pebbles; moderately alkaline (pH 8.2); clear wavy boundary. (5 to 20 inches thick)
AC--17 to 29 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; strongly effervescent; moderately alkaline (pH 8.2); gradual smooth boundary. (10 to 30 inches thick)
C--29 to 60 inches; light brownish gray (10YR 6/2) clay loam, dark grayish brown (10YR 4/2) moist; massive; hard, friable, slightly sticky and slightly plastic; strongly effervescent; common distinct yellowish brown (10YR 5/6) redox features; slightly alkaline (pH 7.6).
TYPE LOCATION: La Plata County, Colorado; about 12 miles southwest of Hesperus, Colorado, on the west side of the La Plata River; located about 2,000 feet west and 600 feet north of the southeast corner of Sec. 5, T. 33 N., R. 12 W.; Mormon Reservoir USGS quad.; Lat. 37 degrees, 07 minutes, 39 seconds N., and Long. 108 degrees, 10 minutes, 15 seconds W.; NAD 27
RANGE IN CHARACTERISTICS:
Soil moisture regime: Ustic moisture regime. The moisture control section is dry for 15 consecutive days from June 1 to July 15 when the soil temperature at 20 inches is greater than 41 degrees F. It is not dry in all parts of the moisture control section for at least 45 consecutive days following the summer solstice to October 20, and for at least 90 cumulative days during that period.
Soil temperature regime: mesic
Mean annual soil temperature: 47 to 54 degrees F
Mean annual summer soil temperature: 60 to 65 degrees F
Particle-size control section: 18 to 35 percent clay, 15 to 60 percent sand, and 15 to 60 percent silt
Depth to redox concentrations: 24 to 60 or more inches
Thickness of the mollic epipedon: 20 to 40 or more inches
Water table: depth is 3 to 5 feet, kind is apparent, months are May and June
Organic carbon: decreases irregularly with depth
Some pedons have buried A horizons
A horizon:
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 1 to 3
Texture: loam or clay loam
Rock fragments: 0 to 5 percent
Calcium carbonate equivalent: 0 to 1 percent
Reaction: neutral to moderately alkaline
AC horizon: if present
Value: 4 or 5 dry, 2 to 4 moist
Chroma: 2 or 3
Texture: loam or clay loam
Rock fragments: 0 to 5 percent
Calcium carbonate equivalent: 1 to 10 percent
Reaction: slightly alkaline or moderately alkaline
Bw horizon: some pedons have a cambic horizon but it is not required
C horizon:
Hue: 2.5Y or 10YR
Value: 4 to 6 dry, 3 or 4 moist
Chroma: 2 or 3
Texture: loam, clay loam, or silty clay loam
Rock fragments: 0 to 5 percent typically, but may range up to 60 percent below one meter in some pedons
Calcium carbonate equivalent: 1 to 10 percent
Reaction: slightly alkaline or moderately alkaline
COMPETING SERIES: These are the Bon, Manzano, Merrick, and St. Onge series. Potential competitors that do not yet have CEA class assigned are the Draper, Frazwell, Humbarger, Lynx, Maskell, Pack, and Shanta series. Bon, Humbarger, Maskell, Merrick, and St. Onge soils are in a climatic setting that receives about 3/4 of their precipitation between April and September. In addition, these soils occur at low elevations and the Humbarger soils have mean annual temperature of greater than 54 degrees F. Bon and St. Onge soils are moist in some parts of the moisture control section from May 15 to July 15. Draper, Frazwell, Lynx, Maskell, Merrick, and Pack soils are leached of carbonates to a depth of 30 inches or more. In addition, Frazwell soils have a buried horizon at 34 to more than 60 inches. Manzano soils have a Bw horizon and a consistent k horizon. Shanta soils have 5 to 20 percent rock fragments in the particle size control section.
GEOGRAPHIC SETTING:
Parent material: alluvium derived from mixed sources
Landform: alluvial fans, low terraces, flood plains, and drainages that dissect uplands
Slopes: 0 to 6 percent
Elevation: 5,400 to 7,400 feet
Mean annual air temperature: 45 to 52 degrees F
Mean annual precipitation: 13 to 20 inches
Wettest months: except for May and June, monthly precipitation is about the same
Driest months: May and June receive the least precipitation, however the soils are still moist from snowmelt through May.
Frost-free period: 100 to 130 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Sycle and Tefton soils.
Sycle soils are underlain by sand, gravel, and cobble.
Tefton soils are somewhat poorly drained soils on flood plains of lower elevations.
DRAINAGE AND PERMEABILITY: moderately well drained, negligible to high runoff, moderately slow to moderate permeability
USE AND VEGETATION: This soil is used mainly for irrigated crops and pasture and livestock grazing. Native vegetation consists of western wheatgrass, needlegrass, mountain muhly, sagebrush, serviceberry, and Gambel oak.
DISTRIBUTION AND EXTENT: Western and southwestern Colorado LRR D, MLRA 39. This series is of minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: La Plata County Area, Colorado, 1982.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon: The zone from 0 to 29 inches. (Ap, AC, and A2 horizons)
Cumulic feature: Has a mollic epipedon more than 20 inches thick and organic carbon does not decrease regularly with depth.
Redoximorphic features: Redox concentrations at 29 to 60 inches.
Soil Taxonomy Second Edition, 1999