LOCATION ATRAC NM+UTEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Ustic Haplocambids
TYPICAL PEDON: Atrac loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 3 inches; brown (10YR 5/3) loam, dark brown (10YR 4/3) moist; weak fine granular structure; soft, very friable, slightly sticky and slightly plastic; few fine roots; few fine pores; mildly alkaline (pH 7.6); abrupt smooth boundary. (1 to 4 inches thick)
Bw1--3 to 9 inches; yellowish brown (10YR 5/4) sandy clay loam, dark brown (10YR 4/3) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common medium and fine roots; few fine pores; mildly alkaline; clear smooth boundary. (0 to 11 inches thick)
Bw2--9 to 24 inches; light brown (7.5YR 6/4) sandy clay loam, dark brown (7.5YR 4/4) moist; moderate medium subangular blocky structure; hard, very friable, sticky and plastic; few fine and medium roots; few fine pores; moderately alkaline; clear smooth boundary. (6 to 20 inches thick)
C1--24 to 44 inches; pale brown (10YR 6/3) sandy clay loam, yellowish brown (10YR 5/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few fine and medium roots; few fine pores; violently effervescent; carbonates disseminated; strongly alkaline; clear smooth boundary. (6 to 40 inches thick)
C2--44 to 56 inches; pale brown (10YR 6/3) sandy loam, yellowish brown (10YR 5/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; few fine pores; violently effervescent; carbonates disseminated; strongly alkaline; abrupt smooth boundary. (O to 20 inches thick).
C3--56 to 60 inches; very pale brown (10YR 7/3) sandy clay loam, yellowish brown (10YR 5/4) moist; massive; hard, friable, slightly sticky and slightly plastic; few fine roots; few fine pores; violently effervescent; carbonates disseminated; strongly alkaline.
TYPE LOCATION: San Juan County, New Mexico; northern part near Colorado state boundary; 1,900 feet north, 1,700 feet east of southwest corner of sec. 29, T. 32 N., R. 11 W.
RANGE IN CHARACTERISTICS: The average annual soil temperature ranges from 47 to 54 degrees F. These soils are usually dry in all parts of the soil moisture control section more than one-half of the time but less than three-fourths of the time, the soil temperature is above 41 degrees F. Forty to fifty percent of the total precipitation comes during July, August, September and October. Less than 4 inches of precipitation is received in July and August and the SMCS is moist intermittently in some part during this period. Twenty-five percent of the yearly precipitation comes in the 120 days following the winter solstice and the SMCS is moist in all parts for about 30 consecutive days during this period. The base of the cambic horizon ranges from 6 to 35 inches in depth. The 10- to 40-inch control section is sandy clay loam, loam, or clay loam and averages 18 to 35 percent clay. Below the control section the texture is loamy sand, sandy loam, loam, sandy clay loam, or clay loam. Some pedons are stratified below the control section. Atrac soils have less than 15 percent calcium carbonate equivalent and does not have secondary carbonates. Depth to bedrock is more than 60 inches.
The A horizon has hue of 10YR or 7.5YR, value of 4 through 6, 2 through 4 moist and chroma of 2 through 4 dry or moist. It is sandy loam, sandy clay loam, loam, very fine sandy loam, or silt loam. It is neutral or mildly alkaline.
The B horizon has hue of 7.5YR through 2.5Y, value of 5 or 6 dry, 4 or 5 moist and chroma of 3 through 6. It is neutral to moderately alkaline.
The C horizon has hue of 7.5YR through 2.5Y, value of 5 through 7 and 4 through 6 moist, with chroma of 2 through 6. It is moderately alkaline or strongly alkaline.
COMPETING SERIES: These are the Edgar, La Fonda, McRae, and Zigweid series. Edgar soils have a calcic horizon. La Fonda soils are not moist for 30 consecutive days following the winter solstice and have secondary carbonates. McRae soils have sola less than 14 inches thick. Zigweid soils have free carbonates within 6 inches of the soil surface.
GEOGRAPHIC SETTING: Atrac soils are on upland hills, benches, terraces, slopes and breaks. They formed in loamy alluvial material derived from sandstone and shale. Slopes range 1 to 15 percent. Elevation range is 6,000 to 7,200 feet. Mean annual precipitation is 10 to 13 inches. Average annual air temperature is 45 to 52 degrees F. The frost-free period is about 100 to 150 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Poleo, Buckle, Shingle, and Travessilla soils. Poleo and Buckle soils have an argillic horizon. Shingle and Travessilla soils have bedrock at a depth of less than 20 inches.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderate permeability.
USE AND VEGETATION: Rangeland. Present vegetation is western wheatgrass, sideoats grama, blue grama, oneseed juniper, pinyon pine, Indian ricegrass, antelope bitterbrush, and big sagebrush.
DISTRIBUTION AND EXTENT: Uplands in northwestern New Mexico, Southern Utah, possibly extending into Colorado. Atrac soils are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: San Juan County, Eastern Part, New Mexico, 1978.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to a depth of about 7.5 cm. (A horizon)
Cambic horizon - the zone from about 7.5 cm. to 61 cm. (Bwl, Bw2 horizons).
OSED scanned by SSQA. Last revised by state on 11/83.