Biochar and Other Amendments Promote Douglas fir Survival and Growth on Mine Tailings
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In the western US, there are over 33,000 abandoned sites where heavy metal contaminated mine tailings contaminate local ground and surface water sources. At these sites, revegetation is required to prevent further erosion of heavy metal contaminated soils into nearby waters. However, successful growth of plants is often limited by degraded soil conditions, including low soil pH and associated high soil heavy metal concentrations, poor soil structure, diminished water holding capacity, limited soil fertility, soil carbon, and microbial activity. In a field study, we evaluated the effects of a mixture of amendments (lime, biosolids, biochar, locally effective microbes) on spoil pH and metal concentrations and subsequent impacts on injury, growth and needle elemental concentrations for Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] growing in mine spoil at the Formosa mine Superfund site in southwestern Oregon. Two years past amendment application, the spoil had a pH increase and lowered metal availability, resulting in enhanced seedling survival, growth, and needle N contents; while reducing needle heavy metal concentrations, such as Cu. This study indicates that biochar, along with lime and nutrients, can enhance tree seedling growth and affect needle elements in mine affected spoils.