Influence of biosolids and fertilizer amendments on physical, chemical and microbiological properties of copper mine tailings

Abstract

A 3-yr field study was conducted on two texturally different tailings sites at the Highland Valley Copper Partnership mine in south-central British Columbia to determine the effects of fertilizer and biosolids amendments on selected soil physical, chemical and microbiological properties. Soil bulk density and penetration resistance decreased in the upper 15 cm of tailings with increasing dry biosolids application rates of 50, 100, 150, 200 and 250 Mg ha-1. The addition of biosolids increased gravimetric water retention at field capacity and wilting point, but no significant changes occurred in the gravimetric water-holding capacity as both field and wilting point increased proportionally. Increasing biosolids decreased volumetric water-holding capacity on the silt loam, but had no effect at the sandy site because of decreased bulk density. Soil pH was not impacted by the treatments while electrical conductivity, soil organic matter, total carbon and cation exchange capacity increased with increasing levels of biosolids applied. Biosolids enhanced biological activity by increasing total aerobic, total anaerobic, iron reducing, sulfate reducing and denitrifying microorganisms near the surface. The fertilizer amendment did not alter soil physical or chemical properties from those of the control. The addition of biosolids was more effective at enhancing properties related to soil quality and fertility and therefore more effective for building soil organic matter on reclaimed tailings sites than the traditional use of inorganic fertilizer.