There are approximately 38,500 abandoned mine-sites in Washington, Oregon, and Idaho that need to be reclaimed so they no longer pose a hazard to humans or wildlife. Revegetation is often hampered on these sites because there is little organic matter within the soil. Using organic amendments may help increase soil organic matter and water holding capacity, leading to successful revegetation of these sites.
RMRS scientists and their collaborators used biochar, wood chips, and biosolids alone and in combination to determine if they can be used to restore soil physical, chemical, and biological functions on abandoned mines in forests across the western United States. In addition, they are evaluating the best methods for revegetation (seeding vs. planting) so that mineral soil organic matter can be rebuilt over time.
Field plots have been initiated on abandoned gold mine dredge sites near Sumpter, Oregon. Researchers collaborated with the Umatilla National Forest to apply biochar, biosolids and/or wood chips. One-half of each plot was seeded while the other one-half was planted with locally adapted seed. Soil temperature and moisture are being recorded every four hours.
Organic amendments have increased soil water holding capacity. Biosolids add a significant amount of nutrients to the site, but because there is little vegetation to use these nutrients, they leach out of the root zone. However, on the planted side of each plot, plants in the biochar and biosolid amended plots are larger and have a greater root mass.