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United States Department of Agriculture

Agricultural Research Service

Title: Bentonite Mine Spoil Revegetation and Long-Term Assessment

item Schuman, Gerald

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: March 6, 2002
Publication Date: March 6, 2002

Interpretive Summary: Abandoned bentonite mine land reclamation is very difficult because of the high clay content, high salinity, and sodicity of the spoil material and the arid-semiarid climate of the region. This paper reviews long-term research that was initiated in 1979 and completed in 2000. Long-term assessment has shown that the use of sawmill byproducts (sawdust, bark and woodchips) and gypsum can successfully be used to correct the high salts, sodium and clay content of these spoil materials and that revegetation is sustainable and productive. This research led to the development of a reclamation technology that has been used to reclaim over 6000 hectares of abandoned bentonite mine spoils in Wyoming and has the potential to be utilized to reclaim over 10,000 additional hectares in Montana and South Dakota.

Technical Abstract: Abandoned bentonite mine spoils are prehaps the most difficult material to successfully rehabilitate because of the nature of the spoil and the climate of the region where bentonite is mined. The major U.S. deposits of bentonite are in the tri-state region of Montana, South Dakota, and Wyoming, an area that is characterized by an arid to semi-arid climate. Bentonite deposits are associated with Cretaceous Age shallow seas which results in the spoil material being of high salinity, high sodium, and high clay content. These conditions combine to create severe water relation problems in the spoil and osmotic stress to plant seedlings. In 1979, research was initiated to evaluate the potential of sawmill residues and gypsum as spoil amendments that would enable water movement into the spoil, ameliorate the high sodium, and allow leaching of the salts and sodium from the root zone. The technology developed by this research has been shown to be effective in rehabilitating abandoned bentonite spoils and has been used to reclaim over 5000 hectares of these lands in Wyoming. Long-term assessment has shown that the highly aline, sodic nature of these spoils can be successfully ameliorated and these lands restored to productivity.

Last Modified: 3/29/2015
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