Alternatives to Topsoil: A Five-Year Case Study in Mine Site Revegetation

Quality topsoil is often a limited resource in mine site revegetation. For this reason, a series of demonstration plots was installed to evaluate the suitability of alternative growth media for revegetation projects in the Coeur d'Alene Mining District of northern Idaho. Plot treatments included biosolids, composts, log yard wastes, and two organic soil treatments. Each plot was seeded with a standardized seed mix and evaluated for revegetation success, nutrient runoff, and soil erosion from 2003 through 2007. All treatments were successful in promoting a self-sustaining vegetative cover. The level of available nitrogen had a strong impact on vegetation coverage, species distribution and extent of unseeded vegetation. For example, high nitrogen treatments promoted a grass-dominated/low forb profile with a low content of unseeded vegetation. In contrast, low nitrogen treatments promoted a more diverse grass-forb mixture with greater susceptibility to unseeded vegetation establishment. The species distribution within most plots also changed over time. In grass-dominated plots, wheatgrass declined with a concurrent increase in brome and fescue. The remaining plots exhibited increases in yarrow, white clover, and milkvetch.