LOCATION GRASSNA ND+MT SDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Pachic Haplustolls
TYPICAL PEDON: Grassna silt loam - on an east-facing concave slope of 1 percent under cropland. When described the soil was moist throughout. (Colors are for dry soil unless otherwise stated)
Ap--0 to 7 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak medium and fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; many roots; many fine pores; neutral; abrupt boundary.
A--7 to 17 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak coarse prismatic structure parting to moderate coarse and medium subangular blocky with some blocks separating to weak platy; hard, friable, slightly sticky and slightly plastic; common roots; many fine pores; neutral; gradual wavy boundary. (Combined A horizons 7 to 20 inches thick)
Bw1--17 to 30 inches; dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak coarse prismatic structure parting to moderate medium and fine subangular blocky; hard, friable, slightly sticky and slightly plastic; common fine roots; common fine pores; few very dark brown (10YR 2/2) moist; clay films on faces of peds; neutral; gradual wavy boundary.
Bw2--30 to 40 inches; dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate coarse and medium prismatic structure parting to moderate medium and fine angular blocky; very hard, friable, slightly sticky and slightly plastic; few fine roots; common fine pores; neutral; clear wavy boundary. (Combined Bw horizons 8 to 30 inches thick)
Bk--40 to 50 inches; pale yellow (2.5Y 7/3) silt loam, light olive brown (2.5Y 5/4) moist; weak subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few fine roots; common fine pores; common fine white carbonate masses; violent effervescence; moderately alkaline; gradual wavy boundary. (7 to 30 inches thick)
C--50 to 60 inches; pale yellow (2.5Y 7/3) silt loam, light olive brown (2.5Y 5/4) moist; common medium distinct gray (5Y 5/1) moist redoximorphic depletions and common fine prominent dark yellowish brown (10YR 4/4) moist redoximorphic concentrations; massive; hard; friable, slightly sticky and slightly plastic; few fine pores; few small carbonate masses; strong effervescence; moderately alkaline.
TYPE LOCATION: Emmons County, North Dakota; 11 miles south of Strasburg; 350 feet south and 45 feet west of the northeast corner, sec. 26, T. 129 N., R. 76 W.
RANGE IN CHARACTERISTICS: The 10- to 40-inch particle-size control section averages between 18 and 30 percent clay. The mollic epipedon typically is more than 30 inches thick but ranges from 16 to 40 inches. Saline phases are recognized.
The A horizon has hue of 10YR, value of 3 to 5 and 2 or 3 moist, and chroma of 1 or 2 dry and 2 moist. It typically is silt loam, but, some is silty clay loam, loam or clay loam with 10 to 30 percent very fine sand. It is slightly acid to slightly alkaline.
The Bw horizon has hue of 10YR, value of 4 or 5 and 2 to 4 moist, and chroma of 2 or 3. In the lower part, it has hue of 2.5Y in of some pedons. Texture is silt loam, loam, clay loam or silty clay loam. It is neutral to moderately alkaline.
The Bk horizon has hue of 10YR or 2.5Y, value of 5 to 7 and 4 or 5 moist, and chroma of 2 to 5. It is silt loam. It is slightly alkaline or moderately alkaline. Some pedons have BC, BCk or 2Bk horizons.
The C horizon has hue of 2.5Y, value of 6 or 7 and 4 to 6 moist, and chroma of 2 to 4. It is silt loam, but, coarser or finer textures are below depths of 40 inches in some pedons. It is neutral to moderately alkaline. Some pedons have visible gypsum in the lower part. Some pedons have Ab horizons below 50 inches.
COMPETING SERIES: These are the Makoti and Wilton series. Makoti soils contain 30 to 35 percent clay in the particle-size control section. Wilton soils have loam or clay loam glacial till horizons within depths of 40 inches.
GEOGRAPHIC SETTING: Grassna soils are on concave, level to gently sloping swales, fans, and foot slopes mainly on silt mantled uplands. Slope ranges from 0 to 6 percent. The soil formed in silty sediments. The climate is cool, semiarid. Mean annual air temperature ranges from 34 to 45 degrees F, and mean annual precipitation ranges from 13 to 18 inches. About three-fourths of the precipitation comes in the spring and summer.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Wilton soils and the Bowbells, Linton, Mandan, Morton, Sen, Temvik and Williams soils. Bowbells, Linton, Morton, Sen, Temvik and Wilton soils are on convex uplands adjacent to the Grassna soils. Mandan soils are on nearby terraces and uplands nearer to the source of loess. Williams soils on nearby glacial till uplands. Bowbells and Williams have argillic horizons and are fine-loamy. Linton and Mandan soils are coarse-silty. In addition, the Linton soils have mollic epipedons less than 16 inches thick. Morton soils have argillic horizons. Sen soils have mollic epipedons less than 16 inches thick and soft siltstone at depths of 20 to 40 inches. Temvik soils have mollic epipedons less than 16 inches thick, and in addition, have glacial till within depths of 20 to 40 inches.
DRAINAGE AND PERMEABILITY: Well or moderately well drained. Runoff ranges from negligible to medium depending on slope. Moderate permeability. Grassna soils receive some runoff from higher lying uplands. A seasonal high water table is at a depth of 3.5 to 5.0 feet at some time during the period of April through June in the moderately well drained phase. It is at a depth of 4 to more than 6 feet during the same period in the well drained phase.
USE AND VEGETATION: Almost all areas of Grassna soils are cropped to small grains, flax, and corn. Native vegetation is green needlegrass, big bluestem, western wheatgrass, and needleandthread grass.
DISTRIBUTION AND EXTENT: Central and western North Dakota and north-central South Dakota. Mainly in the Missouri River basin loess areas. The series is of large extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Burleigh County, North Dakota, November, 1971.
REMARKS: Diagnostic horizons and features recognized in this pedon are: mollic epipedon - the zone from the surface of the soil to a depth of 40 inches (Ap, A, Bw1, and Bw2 horizons).
ADDITIONAL DATA: Laboratory Sample SU74ND-29-2.