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Restoring abandoned mine soil with organic amendments

Date: August 23, 2017

There are over 161,000 abandoned mine sites in the western US that are not vegetated. To improve the soil to begin growing vegetation, we used biochar, wood chips, and/or biosolids. All amendments increased soil cover and increased grass and forb success


Restoring abandoned mine sites with no environmental hazard or chemical contamination can be expensive because of the inhospitable (hot, dry) environment.  However, the large number of abandoned mine sites located across the west make it imperative to begin restoration activities to help shade streams, reduce erosion, provide habitat, and generally improve soil properties. 


To reclaim soils disturbed from mining activity on National Forests new cost-effective strategies are needed. In addition, disposal of waste wood from local timber harvest operations or biosolids from waste water treatment plants can be expensive. Therefore, using organic byproducts for soil reclamation activities on National Forests may provide an opportunity to increase soil cover and productivity, and decrease restoration costs. To test the effectiveness of these amendments for reclamation, a field study was established using organic amendments applied to gold dredgings capped with 10 centimeters of loam and with little regenerating vegetation within the Umatilla National Forest in northeastern Oregon. Study plots had biochar (11 megagrams/hectare), biosolids (17 megagrams/hectare), or wood chips (22 megagrams/hectare) applied singly or in combination. Each plot was divided in half. One half of the plot was seeded with native grasses and forb and the other half was planted with a combination of California brome (Bromus carinatus Hook & Am.) and Jepson’s blue wildrye (Elymus glaucus Buckl.). After two growing seasons, there were no significant differences in plant cover between the planted or seeded plots. Biosolids, biosolid + biochar + wood chips, and biosolid + wood chips had greater grass and forb planted cover after two years; seeded plots on the biosolid + biochar + wood chips and biosolid + wood chip treatments had the greatest grass and forb cover. Soil properties were significantly altered by individual treatments; combination treatments improved nutrient availability and soil moisture, resulting in up to twice as much plant cover than in the control plots. Forest managers can produce biochar and wood chips from the abundant forest waste generated during harvest operations, and class “A” biosolids are available in Oregon from local municipalities. Using these three amendments in combination to restore disturbed mine soils can provide an affordable and effective strategy.

Soil amendment treatments (wood chips, biochar, and biosolids) alone or in combinations applied to an abandoned mine site near Sumpter, OR
Soil amendment treatments (wood chips, biochar, and biosolids) alone or in combinations applied to an abandoned mine site near Sumpter, OR

Key Findings

  • Locally-sourced organic amendments (biochar, wood chips, biosolids) were effective at increasing soil cover and plant growth.

  • Soil amendments were relatively inexpensive

  • Building soil organic matter with forbs and grasses will help improve the soil for supporting trees in the future.


Featured Publications

Page-Dumroese, Deborah S. ; Ott, M. R. ; Strawn, D. G. ; Tirocke, Joanne M. , 2018

Principal Investigators - External: 
Daniel Strawn - University of Idaho (co-PI)
Monica Ott - University of Idaho graduate student
Research Location: 
Oregon, Region 6, Umatilla NF