LOCATION BLACKMAN COTentative Series
TAXONOMIC CLASS: Fine, smectitic, frigid Udic Haplusterts
TYPICAL PEDON: Blackman clay loam - range. (Colors are for dry soil unless otherwise noted.)
A--0 to 7 inches; grayish brown (10YR 5/2) clay loam, very dark grayish brown (10YR 3/2) moist; moderate, medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; neutral (pH 7.2); clear wavy boundary. (5 to 11 inches thick)
Bw--7 to 14 inches; light brownish gray (10YR 6/2) clay, dark grayish brown (10YR 4/2) moist; weak fine subangular blocky structure; hard, firm, very sticky and very plastic; slightly effervescent; mildly alkaline (pH 7.4); gradual wavy boundary. (7 to 31 inches thick)
Bk--14 to 60 inches; light brownish gray (2.5Y 6/2) stratified clay loam and silty clay loam, dark grayish brown (2.5Y 4/2) moist; massive; hard, firm, sticky and plastic; few roots; few very fine pores; fine inconsistent seams of secondary calcium carbonates; strongly effervescent; mildly alkaline (pH 7.8)
TYPE LOCATION: Ouray County, Colorado; about 3-1/2 miles east of Ridgway, in the northeast 1/4 southeast 1/4 of Sec. 11, T. 45 N., R. 8 W.
RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges from 43 to 45 degrees F., and mean summer soil temperature ranges from 58 to 62 degrees F. These soils have cambic horizons that may be noncalcareous in some part. Depth to uniformly calcareous material ranges from 7 to 40 inches. Exchangeable sodium ranges from 0 to 15 percent in most subhorizons of the particle- size control section. There is no subhorizon as much as 3 inches thick above a depth of 20 inches that has as much as 15 percent. Depth to continuous subhorizons of genetically concentrated visible secondary calcium carbonate and/or sulfate ranges from 14 to 50 inches. Mollic colors range from 5 to 10 inches. The 10 to 40 inch particle-size control section is usually clay or heavy clay loam, but on a weighted average basis clay ranges from 35 to 60 percent, silt from 5 to 45 percent, and sand from 15 to 55 percent with more than 15 percent being fine or coarser sand. Rock fragments range from 0 to 35 percent in most subhorizons of the particle-size control section and are mainly 1/2 to 10 inches in diameter. A majority of subhorizons above a depth of 50 inches have a hue of 7.5YR or yellower. Mottling ranges from no mottles to a few faint mottles with the chroma of both matrix and mottles exceeding 2. These soils are dry in some or all parts of the moisture control section more than one-half the time the soil temperature is greater than 41 degrees F.
The A horizon has hue of 2.5Y through 7.5YR, value of 3 through 5 dry, 2 or 3 moist, and chroma of 1 through 3. It is neutral to moderately alkaline.
The Bw horizon, if present, has hue of 2.5Y through 7.5YR, value of 5 through 7 dry, 4 through 6 moist, and chroma of 1 through 6. It ranges from neutral to moderately alkaline.
The Bk horizon has hue of 2.5Y through 7.5YR, value of 5 or 6 dry, 4 or 5 moist, and chroma of 2 through 4. It is moderately or strongly alkaline. Calcium carbonate equivalent of the fine earth ranges from 4 to 14 percent.
COMPETING SERIES: This is the (T) Kissick series. Kissick soils have tonguing in the major part of the particle-size control section and have a lithologic discontinuity at depths of 20 to 32 inches.
GEOGRAPHIC SETTING: Blackman soils are on alluvial fans, terraces, and old flood plains. Slopes range from 0 to 15 percent. The soil formed in alluvium and residuum derived from shale with some influence from glacial materials. Elevation ranges from 7,200 to 8,000 feet. Average annual precipitation ranges from 15 to 20 inches. Average annual temperature ranges from 40 to 44 degrees F. The frost-free period is 70 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cerro and Sunburst soils. Both soils lack extensive cracking.
DRAINAGE AND PERMEABILITY: Moderately well drained; moderate to rapid runoff; slow to very slow permeability.
USE AND VEGETATION: These soils are used for native rangeland and irrigated hayland. Native vegetation consists mainly of western wheatgrass, mountain big sagebrush, and muttongrass.
DISTRIBUTION AND EXTENT: Western Colorado. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: Plateau Valley Soil Conservation District, Mesa County, Colorado, 1945.
REMARKS: This revision documents changes in classification from Vertic Haploborolls and type location transfer from Mesa County, Colorado, to Ouray County, Colorado.