Fecal Indicator Bacteria in Subsurface Drain Water Following Swine Manure Application

Abstract

Appropriate manure application parameters are necessary to maximize nutrient utilization by plants from manure while minimizing water pollution potential. This study focused on the movement of bacteria to receiving tile drains following swine manure application. Specifically, the impacts of different manure application regimes on fecal coliform (FC), Enterococcus (EN), and Escherichia coli (EC) densities in subsurface tile drain water were examined for three years. Manure treatments, including fall, spring, and late winter application at a recommended rate of 168 kg N ha-1 (1X) and at 336 kg N ha-1 (2X) were compared with a non-manure treatment where commercial urea-ammonium nitrate (UAN) was applied. Results indicate that flow-weighted average and maximum observed EN and EC levels in tile water were significantly higher where manure had been applied during late winter at the 2X rate versus the UAN and fall treatments. Levels of FC were highly variable, and the spring injection 1X treatment yielded the highest flow-weighted average and maximum tile water FC levels. Results of this study suggest that manure broadcast onto frozen ground may lead to significantly elevated EN and EC levels in tile water in similar environments, especially when applied in excess of crop nutrient requirements.