RECLAMATION OF FOREST SITES DISTURBED BY MINING ACTIVITY USING ORGANIC AMENDMENTS

With over 30,000 abandoned mines on Forest Service land, efficient and affordable reclamation methods are needed to restore forest resources and productivity. Surface applied organic amendments, biochar, biosolids, and woodchips, provide cheap, sustainable solutions that will improve soil quality and promote re-vegetation. In this project we are investigating amendment effects on soil quality at an abandoned dredge tailings site in the Umatilla Forest of NE Oregon. Experimental plots of the three amendments, applied singly and in combination, are being sampled bi-annually over the course of three years to measure changes in soil quality and plant success. Available nutrients were analyzed at two depths. Soil moisture and temperature were monitored with in-situ data loggers, and soil water holding properties were measured using pressure plates and a Dew Point potentiometer. Results from the first year of monitoring show increases in pH, organic carbon, macronutrients (K, P, Ca), and total nitrogen in all treatments. Biosolids had the most improvement in soil quality parameters. Nutrient changes were observed in plots containing woodchips and biochar, however weathering of these larger particles takes time under field conditions, and thus changes in soil nutrient availability will likely take longer than 1 year. Amendments caused an increase in water content at field capacity, especially in the surface layer of all amendment plots. Although changes are pronounced in single amendment applications, the combination of all three amendments may induce longer lasting, more stable plant growth by providing a combination of soil quality improvements. Results suggest that surface amendment of biochar, woodchips, and biosolids for land reclamation of disturbed forest sites are a promising technology for remediating degraded soils in the Pacific Northwest.