LOCATION MCRAE MT+WYEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Aridic Haplustepts
TYPICAL PEDON: McRae loam - cultivated. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 5 inches; light brownish gray (2.5Y 6/2) loam, dark grayish brown (2.5Y 4/2) moist; coatings on granules of grayish brown (2.5Y 5/2) dry and very dark grayish brown (2.5Y 3/2) moist; weak medium granular structure; slightly hard, very friable, slightly sticky, nonplastic; abrupt boundary.
B2--5 to 11 inches; grayish brown (2.5Y 5/2) loam, dark grayish brown (2.5Y 4/2) moist; coatings on peds of dark grayish brown (2.5Y 4/2), very dark grayish brown (2.5Y 3/2) moist; moderate medium prismatic structure; hard, very friable, slightly sticky, slightly plastic; thin patchy clay films; clear boundary. (6 to 9 inches thick)
C1ca--11 to 34 inches; pale olive (5Y 6/3) loam, olive (5Y 5/3) moist; very weak coarse prismatic structure in upper part, becoming massive and stratified in lower part; hard, friable, slightly sticky, slightly plastic; moderate effervescence with few seams and soft nodules of segregated lime; gradual boundary. (20 to 30 inches thick)
C2--34 to 60 inches; pale olive (5Y 6/3) loam, olive (5Y 5/3) moist; massive; slightly hard, friable, slightly sticky, slightly plastic; moderate effervescence.
TYPE LOCATION: Yellowstone County, Montana; 1,350 feet south and 330 feet east of W1/4 corner sec. 19, T.4N., R.33E.
RANGE IN CHARACTERISTICS: The McRae soils are usually dry between depths of 4 and 12 inches but are not dry in all parts above 12 inches for more than half the time that soil temperature at 20 inches is more than 41 degrees F. The mean annual soil temperature is about 48 degrees F. The solum is 11 to 14 inches thick. The soil between depths of 10 and 40 inches is loam or light clay loam with 18 to 30 percent clay and more than 15 percent fine and coarser sands. The soil is moderately or strongly alkaline. Conductivity of the saturation extract ranges from 1 to 3 millimhos per cm. These soils are generally nonsaline. The Ap and B2 horizons are noncalcareous or weakly calcareous. Hue is 10YR through 5Y.
The Ap horizon has value of 5 or 6 dry and 3.5 through 5 moist. Its granules are coated one-half to one unit of value darker.
The B2 horizon has dry and moist value of the crushed soil the same as in the Ap horizon, and has coated colors one-half unit darker. The chroma is 2 or 3.
The C horizon has value of 5 or 4 moist. It has less than 5 percent mottles of segregated lime and has an estimated 8 to 12 percent CaC03 equivalent.
COMPETING SERIES: These are the Edgar and Menoken series. Edgar soils have a prominent horizon of lime accumulation with dry value of 7 or more. Menoken soils have less than 15 percent fine and coarser sand in the 10- to 40-inch control section.
GEOGRAPHIC SETTING: McRae soils are on terraces of rivers and streams, alluvial fans in valleys, and footslopes in the uplands. They formed in calcareous loam alluvium from soils developed over sedimentary rocks. The mineralogy of the alluvium is mixed. The climate is semiarid with a mean annual precipitation of 8 to 14 inches and mean annual temperature of 45 to 50 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bainville, Cushman, Elso, Fort Collins, Havre, and Midway soils. Bainville, Cushman, Elso and Midway soils are on the uplands occupying hills and ridges, and the Fort Collins and Havre soils are in valleys. Bainville, Cushman, Elso and Midway soils have shale bedrock at depths ranging shallower than 40 inches, and Cushman and Fort Collins soils have Bt horizons. Havre soils occur on river and stream flood plains and have no horizonation.
DRAINAGE AND PERMEABILITY: Well-drained; moderate permeability; slow to medium runoff.
USE AND VEGETATION: Principally used for irrigated cripland. Used also for rangeland. Principal native vegetation is mixed short and mid grasses and forbs.
DISTRIBUTION AND EXTENT: Southeastern Montana where they are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Treasure County, Montana, 1961.
REMARKS: The McRae soils were formerly classified as Brown soils.
OSED scanned by SSQA. Last revised by state on 6/71.