Designing Amendments to Improve Plant Performance for Mine Tailings Revegetation
To provide recommendations for establishment of plants on a low pH mine tailings, we conducted greenhouse studies on the effects of gasified conifer softwood waste biochar (BC) plus other amendments to improve the survival and growth of plants. Experiment 1 indicated that 1% lime (by weight) raised tailings pH, permitting Douglas fir (Pseudotsuga menziesii) seedling growth. However, high biosolids (BS, 2% by weight) were phytotoxic likely due to salts associated with high electrical conductivity (EC). Biochar (BC. 1, 2.5 or 5% by weight) plus lime and BS, caused an additional increase in pH, a decrease in EC, and enhanced growth of Douglas fir. Experiment 2 with Douglas fir had additional amendments: lime ( 0.5 and 1% by weight), two nutrient sources (BS and mineral fertilizer), three nutrient levels, (0.2, 0.5, 2%), BC (0 and 2.5%), and Locally-Sourced Microbes (LSM) or no LSM. While there were many interactions among amendments, in general Douglas fir growth again was enhanced with lime, biochar, and lower concentrations of nutrients. LSM had no effect on Douglas fir seedlings in either study. These studies indicated optimum additions of BC in combination with other amendments to enhance revegetation of low pH, metal-contaminated mine tailings.