LOCATION PACTOLA SD
Established Series
Rev. ACM-KEC
12/2021
PACTOLA SERIES
The Pactola series consists of deep and very deep,well drained soils formed in residuum from steeply dipping beds of metamorphic rock on mountains. They have moderate permeability. Slopes range from 6 to 60 percent. Mean annual air temperature is about 40 degrees F, and the annual precipitation is about 22 inches.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Glossic Hapludalfs
TYPICAL PEDON: Pactola loam - on a 20 percent convex southeast-facing slope under a ponderosa pine forest at 53l5 feet elevation. When described the soil was dry throughout. (Colors are for dry soil unless otherwise stated.)
Oi--0 to 1 inch: forest litter and partially decayed litter. (l to 3 inches thick)
A--1 to 3 inches; dark gray (10YR 4/1) loam, black (10YR 2/1) moist; weak thin platy structure parting to weak very fine granular; soft, very friable; many fine roots; few fine fragments of rock; slightly acid; abrupt smooth boundary. (0 to 2 inches thick)
E--3 to 10 inches; light gray (10YR 7/2) very channery silt loam, dark grayish brown (10YR 4/2) moist; weak thin platy structure; soft, very friable; many fine and medium roots; 45 percent by volume of fragments of rock; moderately acid; clear wavy boundary. (4 to 14 inches thick)
B/E--10 to 23 inches; grayish brown (10YR 5/2) very channery clay loam, dark grayish brown (10YR 4/2) moist (Bt) and light gray (10YR 7/2) channery silt loam, dark grayish brown (10YR 4/2) moist (E); weak fine and medium subangular blocky structure; slightly hard, friable; common fine and medium roots; 50 percent by volume of fragments of rock; moderately acid; gradual wavy boundary. (0 to 15 inches thick)
Bt--23 to 46 inches; brown (10YR 5/3) extremely flaggy clay loam, brown (10YR 4/3) moist; moderate fine subangular blocky structure of fine earth; slightly hard, firm, slightly sticky and slightly plastic; common fine to coarse roots; 75 percent by volume of fragments of rock; moderately acid; diffuse wavy boundary. (12 to 25 inches thick)
C--46 to 60 inches; light olive brown (2.5Y 5/3) extremely flaggy silt loam, very dark grayish brown (2.5Y 3/2) moist; massive; soft, friable; few medium and coarse roots; 75 percent by volume of fragments of rock; slightly acid.
TYPE LOCATION: Lawrence County, South Dakota; about 5 miles west and 3 miles south of Nemo; 550 feet north and 1340 feet west of the southeast corner of sec. 11, T. 2 N., R. 4 E.
RANGE IN CHARACTERISTICS: Depth to consolidated bedrock ranges from 40 to 60 inches or more. Depth to fractured bedrock containing soil material and with evidence of rock structure is between depths of 20 and 50 inches. The bedrock is tilted. Content of rock fragments ranges from 25 to 70 percent by volume the solum and 40 to 80 percent of the C horizon. Interfingering of the albic horizon into the argillic horizon is in most pedons. The B/E horizon is part of the argillic horizon. The control section averages between 27 and 35 percent clay.
The A horizon has hue of 10YR, value of 4 or 5 and 2 or 3 moist, and chroma of 1 or 2. It is loam, silt loam, channery loam, or channery silt loam, very channery loam, and very channery silt loam. It is moderately acid or slightly acid.
The E horizon has hue of 10YR or 2.5Y, value of 5 to 7 and 3 to 6 moist, and chroma of 1 to 3. Color with value of 3 moist is inherent to the bedrock. It is silt loam and loam, and contains up to 60 percent channers. It is moderately acid or slightly acid.
The B/E horizon has colors of the Bt and E horizon. It is silty clay loam and clay loam and contains 35 to 60 percent channers. It is moderately acid or slightly acid.
The Bt horizon has hue of 10YR or 2.5Y, value of 5 to 7 and 4 to 6 moist, and chroma of 3 to 5. It is clay loam or silty clay loam, and contains 35 to 70 percent channers and flagstones. Content of clay ranges between 27 and 35 percent but some pedons contain up to 40 percent clay in the upper part. It is moderately acid or slightly acid.
The BC horizon when present has hue of 10YR or 2.5Y, value of 5 to 7 and 4 to 6 moist, and chroma of 2 to 5. It is loam or silt loam and contains 50 to 80 percent flagstones. It ranges from moderately acid to neutral.
The C horizon has hue of 10YR or 2.5Y, value of 5 to 7 and 4 to 6 moist, and chroma of 2 to 5. It is loam or silt loam and contains 50 to 80 percent flagstones. It ranges from moderately acid to neutral.
COMPETING SERIES: These are the
Abreu,
Grizzly,
Macmeal,
Mocmont,
Rockoa,
Tecolote,
Vanocker,
Wahatoya, and
Yourame series. Abreu and Macmeal soils do not have a E horizon. In addition, Abreau soils have igneous pebbles and Macmeal soils have carbonates at depths of 24 to 55 inches. Grizzly soils contain more clay in the lower part of the argillic (Bt) horizon and have thicker E horizons. Rockoa soils contain more sand and have coarse fragments of sandstones as stones. Tecolote soils have redder hue in the argillic horizon.
Trapps and Vanocker soils have horizons with accumulations of carbonates. Wahatoya soils contain more sand and have sandstone pebbles and cobbles. Yourame soils have thicker combined E and E/B or B/E horizons.
GEOGRAPHIC SETTING: Pactola soils are on sloping to very steep mountains at elevations of 3600 to 6300 feet. Slope gradients range from 6 to 60 percent. These soils formed in residuum from metamorphic rocks containing mica. Mean annual temperature ranges from 37 to 45 degrees F, and the mean annual precipitation ranges from 18 to 26 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing
Grizzly series and the
Buska,
Heely,
Hisega, and
Virkula series. The Buska, Grizzly, and Virkula soils are on similar landscapes. Buska soils contain more mica.
Citadel and Virkula soils contain less than 35 percent coarse fragments of rock. Heely soils are on similar landscapes and have a mollic epipedon. Hisega soils typically are on steeper landscapes and do not have argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained. Runoff is medium to very rapid. Permeability is moderate.
USE AND VEGETATION: Used for timber production, for recreation and wildlife, and for grazing. Native vegetation is dominantly ponderosa pine with lesser amounts of Black Hills spruce, aspen, and birch. The understory is sparse amounts of shrubs and grasses.
DISTRIBUTION AND EXTENT: Black Hills in western South Dakota and possibly eastern Wyoming. The Pactola series is of moderate extent.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Salina, Kansas
SERIES ESTABLISHED: Lawrence County, South Dakota, 1977.
REMARKS: Diagnostic horizons and features recognized in this pedon are: ochric epipedon - the zone from the surface of the soil to a depth of about 10 inches (A, E horizons); argillic horizon - the zone from about 10 to 46 inches (B/E, Bt horizons). Depths were adjusted to account for the current standard of measuring O horizons. JCW 12/21.
ADDITIONAL DATA: NSSL lab data 76PO716-20 is for the typical pedon.
National Cooperative Soil Survey
U.S.A.