Tokul -- Washington State Soil

Photograph of hilly and mountainous terrain. The landscape vegetation is a forest with occasional openings.

Photograph of the profile of a typifying pedon of Tokul soil series.

Tokul Soil Profile

Surface layer: organic material
Subsurface layer: very dark grayish brown gravelly loam
Subsoil - upper: dark brown gravelly loam
Subsoil - lower: light yellowish brown gravelly loam
Substratum: light brownish gray and dark gray gravelly sandy loam (very hard, dense glacial till cemented by a combination of iron, aluminum, and organic matter)
The name “Tokul” is derived from a small community and creek in King County, Washington. The State of Washington has more than 1,000,000 acres of Tokul soils. These soils are on the western side of the Cascade Mountains along the Puget Trough, from south of Seattle north to the Canadian border. Washington was the first state to recognize soils that formed in volcanic ash (Andisols) as a state soil.

Tokul soils are among the most productive soils in the world. These soils support Douglas-fir and other conifer trees, which are the source of Washington’s nickname, “the Evergreen State.” The State of Washington has hundreds of soils that are influenced by volcanic ash. These “volcanic” soils are used for crop production, timber production, livestock grazing, recreation, and watershed. Most areas of Tokul soils are used for timber production, but some of the smaller areas are used as pasture and for urban development. Tokul soils are limited as sites for homes. Water perches above the dense glacial till during wet periods, making steep slopes unstable.

Small scale map of the state of Washington showing the distribution of Kokul soil series.

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