LOCATION AMODAC WYEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Sodic Ustic Haplocambids
TYPICAL PEDON: Amodac fine sandy loam--rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 4 inches; pale brown (10YR 6/3) fine sandy loam, dark grayish brown (10YR 4/2) moist; weak fine granular structure; soft, very friable, slightly sticky and slightly plastic; many fine roots; slightly effervescent, carbonates disseminated; moderately alkaline (pH 8.0); abrupt smooth boundary. (1 to 5 inches thick)
BA--4 to 7 inches; yellowish brown (10YR 5/4) sandy clay loam, dark grayish brown (10YR 4/2) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; slightly effervescent, carbonates disseminated; moderately alkaline (pH 8.2); clear wavy boundary. (0 to 6 inches thick)
Bw--7 to 15 inches; light brownish gray (2.5Y 6/2) loam, dark grayish brown (2.5Y 4/2) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; hard, friable, slightly sticky and slightly plastic; few fine roots; strongly effervescent, carbonates disseminated and as common distinct coatings on faces of peds; strongly alkaline (pH 9.0); clear wavy boundary. (6 to 17 inches thick)
Bn--15 to 21 inches; light brownish gray (2.5Y 6/2) loam, dark grayish brown (2.5Y 4/2) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; hard, friable, slightly sticky and slightly plastic; few fine roots, strongly effervescent, carbonates disseminated and as common distinct coatings on faces of peds; very strongly alkaline (pH 9.4); clear wavy boundary. (4 to 18 inches thick)
Bnk--21 to 26 inches; grayish brown (2.5Y 5/2) sandy clay loam, dark grayish brown (2.5Y 4/2) moist; massive; hard, friable, slightly sticky and slightly plastic; violently effervescent, carbonates disseminated and as common medium soft masses; very strongly alkaline (pH 9.4); gradual wavy boundary. (4 to 9 inches thick)
C--26 to 60 inches; grayish brown (2.5Y 5/2) sandy clay loam, dark grayish brown (2.5Y 4/2) moist; weak medium platy shale rock structure; hard, friable, slightly sticky and slightly plastic; violently effervescent, carbonates disseminated and as few filaments and soft masses between plates inherited from the parent material; very strongly alkaline (pH 9.2).
TYPE LOCATION: Natrona County, Wyoming; about 2.7 miles NW of the town of Powder River; 1,700 feet east and 2,400 feet north of the SW corner of sec. 21, T. 36 N., R. 85 W.
RANGE IN CHARACTERISTICS: Depth to the base of the cambic horizon ranges from 11 to 25 inches. The cambic horizon includes the Bw and Bn horizons. Calcium carbonate equivalent is less than 15 percent throughout. The particle-size control section is loam, sandy clay loam, or clay loam with 20 to 35 percent clay and 15 to 35 percent fine sand or coarser. The mean annual soil temperature ranges from 47 to 52 degrees F.
The A horizon has hue of 10YR or 2.5Y, value of 5 or 6 dry, 3 through 5 moist, and chroma of 2 or 3. A vesicular crust is on some pedons. EC is less than 2 mmhos. It is moderately alkaline or strongly alkaline.
The Bw horizon has hue of 10YR or 2.5Y, value of 5 or 6 dry, 3 through 5 moist, and chroma of 2 through 4. EC is less than 2 mmhos. It is moderately alkaline or strongly alkaline.
The Bn horizon has hue of 10YR or 2.5Y, value of 5 or 6 dry, 4 or 5 moist, and chroma of 2 or 3. ESP ranges from 15 to 30. EC ranges from 2 to 4 mmhos.
The Bnk or Bnky horizon in some pedons has hue of 10YR or 2.5Y, value of 5 or 6 dry, 4 or 5 moist, and chroma of 2 or 3. ESP ranges from 15 to 30 percent. EC ranges from 2 to 4 mmhos. It is strongly alkaline or very strongly alkaline.
The C horizon has hue of 10YR or 2.5Y, value of 5 or 6 dry, 4 or 5 moist, and chroma of 2 or 3. Soft masses of carbonate, gypsum, and more soluble salts are inherited from the parent material. EC is greater than 4 mmhos. It is strongly alkaline or very strongly alkaline.
COMPETING SERIES: These are the Atrac, Edgar, La Fonda, McRae, Querencia, and Zigweid series. These soils have less than 15 percent exchangeable sodium in the control section.
GEOGRAPHIC SETTING: Amodac soils are on convex slopes of rolling uplands. They formed in material weathered from sodic shale. Slopes range from 2 to 12 percent. The mean annual precipitation ranges from 10 to 14 inches, and the mean annual temperature is 45
to 51 degrees F. Elevation ranges from 5,000 to 6,100 feet. The frost-free season ranges from 110 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cadoma, Hiland, and Keyner soils. Cadoma soils are fine and have a paralithic contact at 20 to 40 inches. Hiland soils have an argillic horizon. Keyner soils have a natric horizon.
DRAINAGE AND PERMEABILITY: Well drained; runoff is medium or rapid; permeability is moderately slow.
USE AND VEGETATION: These soils are used mainly for livestock grazing and wildlife habitat. Native vegetation is mainly rhizomatous wheatgrass, prairie junegrass, Sandberg bluegrass, and birdfoot sagebrush.
DISTRIBUTION AND EXTENT: Central Wyoming. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Natrona County, Wyoming; 1985.