LOCATION SONYOK                  MT

Established Series
Rev. MJH-GLS-KLS
05/2023

SONYOK SERIES

The Sonyok series consists of very deep, very poorly drained sodium affected soils in swales and on low fan terraces in the Hot Springs Valley. These soils formed in alluvium and lacustrine deposits. Slopes are 0 to 4 percent. Elevation is 790 to 880 meters. The average annual precipitation is about 310 mm; the average annual air temperature is about 7 degrees C.

TAXONOMIC CLASS: Fine, mixed, active, nonacid, frigid Aeric Halaquepts

TYPICAL PEDON: Sonyok silty clay loam, 0 to 4 percent slopes, in pasture. (Colors are for moist soils unless otherwise noted.)

Oi--0 to 8 cm; undecomposed and partially decomposed matted roots.

Ap--8 to 26 cm; grayish brown (10YR 5/2) silty clay loam, light gray (10YR 7/2) dry; many fine distinct light olive brown (2.5Y 5/6) redox concentrations; moderate medium subangular blocky structure; hard, firm sticky and plastic; many very fine, fine, and medium roots; common fine tubular pores; neutral (pH 6.8); clear smooth boundary. (15 to 20 cm thick)

Bwn1--26 to 46 cm; brown (10YR 4/3) silty clay, very pale brown (10YR 7/3) dry; many fine distinct light olive brown (2.5Y 5/6) redox concentrations; strong medium angular blocky structure; very hard, very firm, sticky and plastic; common fine and medium roots; many fine tubular pores; slightly alkaline (pH 7.4); clear smooth boundary. (15 to 25 cm thick)

Bwn2--46 to 71 cm; yellowish brown (10YR 5/4) silty clay, pale brown (10YR 6/3) dry; many fine distinct light olive brown (2.5Y 5/6) redox concentrations; moderate coarse subangular blocky structure; very hard, very firm, sticky and plastic; few fine roots; few fine tubular pores; slightly alkaline (pH 7.6); abrupt smooth boundary. (Combined thickness - 35 to 90 cm thick)

C--71 to 160 cm; pale brown (10YR 6/3) silty clay, light gray (10YR 7/2) dry; massive, distinct, 3 to 6 mm varves; very hard, very firm, sticky and plastic; moderately alkaline (pH 8.0).

TYPE LOCATION: Sanders County, Montana; about 775 meters south and 400 meters west of the NE corner of sec. 2, T. 21 N., R. 24 W.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature--6 to 8 degrees C
Soil moisture control section--approximately 10 to 30 cm
Depth to seasonal high water table--ponded to 30 cm
Depth to varved lake sediments--50 to 150 cm

Ap horizon
Hue--10YR or 2.5Y
Value--6 or 7 dry; 4 or 5 moist
Chroma--1 or 2
Clay content--27 to 40 percent
Sodium adsorption ratio--4 to 13
Reaction--pH 6.6 to 7.3

Bwn1 & Bwn2 horizons
Hue--10YR, 2.5Y or 5Y
Value--6 or 7 dry; 4 or 5 moist
Chroma--3, 4, or 6
Texture--silty clay or silty clay loam
Clay content--35 to 60 percent
Electrical conductivity--1 to 4 mmhos/cm
Sodium adsorption ratio--13 to 40
Reaction--pH 7.4 to 7.8

C horizon
Value--6, 7 or 8 dry; 5, 6 or 7 moist
Texture--silty clay, clay, or silty clay loam
Clay content--35 to 50 percent
Electrical conductivity--1 to 3 mmhos/cm
Sodium adsorption ratio--4 to 30
Reaction--pH 7.9 to 8.4

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING:
Landform--broad swales and on lake plains and terraces
Elevation--790 to 880 meters
Slope--0 to 4 percent
Parent material--alluvium and lacustrine material
Climate--long, cold winters; moist springs and falls; hot, dry summers
Mean annual precipitation--250 to 360 mm
Mean annual air temperature--5 to 7 degrees C
Frost-free period--105 to 125 days

GEOGRAPHICALLY ASSOCIATED SOILS: None listed.

DRAINAGE AND PERMEABILITY: Very poorly drained; very slow permeability.

USE AND VEGETATION: Sonyok soils are used mainly for pasture and hayland. There are no known areas of native vegetation. Estimated potential native vegetation is grasses, sedges and rushes.

DISTRIBUTION AND EXTENT: Sonyok soils are of limited extent in the Hot Springs Valley of northwestern Montana; MLRA 44A.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Sanders County, Montana, 1997.

REMARKS: Soil interpretation record: MT1222.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon--8 to 26 cm (Ap horizon)
Cambic horizon--26 to 71 cm (Bwn horizons)
Aquic conditions; horizons with distinct high chroma mottles--8 to 71 cm (Ap, Bwn horizons)
Particle-size control section--25 to 100 cm

Sonyok soils have a frigid temperature regime and an aquic soil moisture regime.

Converted to metric and O horizons were updated to start at zero. Competing series section was not updated. 05/2023

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National Cooperative Soil Survey
U.S.A.