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Fecal bacterial losses in runoff from conventional and no-till pearl millet fertilized with broiler litter

Jenkins, M. B., Truman, C. C., Franklin, D. H., Potter, T. L., Bosch, D. D., Strickland, T. C., Nuti, R. C.
Agricultural water management 2014 v.134 pp. 38-0
Escherichia coli, Pennisetum glaucum, Salmonella, Ultisols, agricultural runoff, bacteria, conventional tillage, glyphosate, irrigation, no-tillage, nonpoint source pollution, pathogens, poultry manure, public health, rain intensity, risk, soil amendments, soil treatment, soil water content, water pollution, weeds, Georgia
Georgia farmers are increasing preemergence applications of soil residual herbicides to control glyphosate resistant weeds. To be effective these herbicides must be activated by post-application irrigation. Broiler litter is often applied to fields before these herbicides. This wetting-in practice increases surface soil water content and may increase runoff and transport of broiler litter borne fecal bacteria into surface waters during subsequent storm events. Our objective was to determine differences in loads of fecal bacteria, Escherichia coli and Salmonella spp., in runoff from conventional tillage (CT) and no-till (NT) systems after herbicides were watered into an Ultisol fertilized with broiler litter. To replicated 6 m2-plots (n = 3) variable rainfall intensity was simulated for 70 min with composite runoff samples collected every 5 min and analyzed for E. coli and Salmonella spp. Although total runoff from the CT plots was significantly greater than from NT plots, no differences in total load of E. coli and Salmonella were observed. No differences in percent of total loads of E. coli and Salmonella recovered in runoff between tillage systems were observed. Total percentage of Salmonella recovered in runoff from both tillage systems was, however, four log10 orders of magnitude greater than the percentage of E. coli that was recovered. Difference in percentage recovered between the fecal indicator bacterium, E. coli, and the pathogen, Salmonella, underscores an apparent difference in hydrologic transport characteristics of these two fecal bacteria and casts doubts on the efficacy of E. coli as an indicator of risk to public health.