Citation:

Molina, M., G. Whelan, AND Tom Purucker. Effect of Season on the Persistence of Bacterial Pathogens in Runoff from Agricultural Plots. Presented at International Symposium on Waterborne Pathogens, Savannah, GA, April 13 - 14, 2015.

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Presented at the International Symposium on Waterborne Pathogens in Savannah, GA, April 13-14, 2015.

Description:

Runoff from agricultural fields undergoing manure applications may carry a variety of chemical and microbial contaminants that compromise water quality and increase the possibility of human exposure to pathogenic microorganisms when recreational waters are impacted. A series of rainfall simulation experiments were implemented to understand and compare microbial release, persistence, and transport mechanisms of fecal pathogens and indicators from animal-derived sources during runoff-producing rainfall events. A set of four rainfall simulations were conducted over different seasons on a field containing 36 plots (0.75 x 2m each). Chicken litter, liquid swine manure, and solid cattle manure were applied to all individual plots the first week ofthe experiment and aged for up to two weeks under field conditions before rainfall application. A constant rate of simulated rainfall was applied for 60 minutes after initiation of runoff, with applications occurring at 0, 1, and 2 weeks. Runoff was collected at various time intervals throughout the rainfall application and analyzed for E. coli 0157, Salmonella, Giardia, Cryptosporidium, enterococci, and E. coli. Results indicated that most of the Giardia was recovered during the first day after application, with negligible amounts recovered one and two weeks after application. Analysis of the effect of season on the persistence of all individual pathogens and indicators by fecal source revealed shorter half-lives for rainfall events occurring during hotter, drier, summer conditions (events 3 and 4} versus events occurring during colder, wetter, winter conditions (events 1 and 2}. In contrast, up to 50% of applied Cryptosporidium was recovered up to two weeks after application during drier conditions. Low levels of Salmonella were also recovered up to two weeks after application, only from plots fertilized with chicken litter during the drier months. This study revealed that aged manures can be a considerable source of fecal indicator and pathogen contamination to surface waters. The type of pathogen surviving in aged manures and transported in runoff depends on the type of livestock manure used as fertilizer and the season when application occurs.

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