Sediment, Nutrient, and Bacteria Runoff from Biosolids and Commercial Fertilizers under Simulated Rainfall

Pollutants from biosolids and commercial fertilizer (CF) land applications may be included in surface runoff and contribute to nonpoint-source pollution. Rainfall simulations were conducted in 2009 to determine the efficacy of a narrow vegetative filter strip (VFS) in reducing nutrient losses. No differences were detected among treatments for total suspended solids (TSS) and colony-forming units (CFUs). Statistically lower nutrient losses were also not detected between CF treatments, yet some forms of nutrients were nearly three times higher in the runoff when a VFS was not employed. Lower levels of certain nutrients were observed when fertilizing with a low rate of biosolids (LB) with a VFS vs. a LB without a VFS orthogonal contrast. These results indicate VFS have the potential to reduce pollutant levels in surface runoff from biosolids and CF. In addition, rainfall simulation studies were performed in 2010 to compare pollutant losses from biosolids or CF amended plots with or without pre-irrigation before a runoff producing event. Differences among treatments were not observed for TSS and CFUs. Pre-irrigation significantly decreased certain forms of nitrogen (N) and phosphorus (P) in surface runoff. Losses of these nutrients were greatest from the non-irrigated CF treatments, which received similar N and P levels as the LB treatments. Results of this study suggest that under similar conditions of vegetative cover and rainfall, CF can contribute more pollutants to surface runoff than biosolids, but nutrient loading is reduced if small rainfall events precede a runoff event