Sewage Sludge as a Coal Mine Spoil Amendment for Revegetation in Colorado

Abstract

AbstractUse of digested municipal sewage sludge as an amendment for revegetation of a Colorado coal mine spoil was evaluated as a function of application rate. Plant growth responses to sewage sludge additions were compared to inorganic nitrogen (N) and phosphorus (P) fertilizer treatments on a grass pasture mixture. Sewage sludge additions resulted in significant increases in aboveground biomass and percent canopy cover over the control for two seasons of growth following sludge application. Sewage sludge rates < 83 Mg ha−1 yielded greater plant growth than any of the inorganic N and P fertilizer treatments for both growing seasons. However, the lowest level of sewage sludge (14 Mg ha−1) resulted in equivalent total N and total P concentrations of the seeded grasses when compared to the highest inorganic fertilizer treatments. The superior growth associated with sewage sludge additions at less than 83 Mg ha−1 was likely due to measured increases in nutrient availability, improved physical condition of the spoil and a possible stimulation of microbial activity. The highest level of sewage sludge (83 Mg ha−1) was detrimental to seeded grass growth when compared to the lower sludge rates in 1984. This may have been due to increased soluble salt concentrations, an increase in competition by invading annual forbs, and/or elemental toxicities. Further research is necessary to determine the exact causes.