TRANSPORT OF SALMONELLA SPP. AND INDICATOR BACTERIA TO DRAINAGE TILE WATERS UNDER CORNFIELDS RECEVING POULTRY MANURE

E. coli and enterococci are commonly used as pathogen indicators in surface water, however, the transport of these bacteria to drainage tiles from manure application fields and the correlation of these indicators to pathogens in this setting is poorly understood. Salmonella spp. is prevalent in poultry litter and is a pathogen that has the potential to be transported to tile waters and ultimately to impact waters that are used for recreation. In this study, concentrations of E. coli, enterococci and Salmonella spp. were measured in tile waters below chisel-plowed and no-till cornfields where poultry manure was applied in late spring (May). Samples were obtained from early May to September in 2010 and 2011. Record high precipitation fell during the sampling period in 2010 and very little precipitation occurred in 2011. Grab samples were taken directly from flowing tiles after every significant rainfall event (>2 cm) and samples were collected hourly throughout selected events using automatic samplers. The combined effects of flow, tillage, time elapsed after application, and application rates were analyzed. Bacteria concentrations in grab samples were consistently higher under no-till plots, where macropores are connected to the surface. Event samples showed bacterial concentrations rose first during or shortly after the rainfall event (prior to any significant increase in tile flow), then a second peak occurred as the tile flow increased sharply due to the event (the rising limb of the hydrograph). This macropore signature occurred under both chisel-plowed and no-till plots. Salmonella spp. were detected on selective media in the majority of post-application samples, however, counts were highly variable due to interference from other bacteria and analysis by qPCR is ongoing.