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Storm events that increase flow rates can disturb sediments and produce overland runoff in watersheds with animal agriculture, and, thus, can increase surface water concentrations of fecal bacteria and risk to public health. We tested the hypothesis that strategically designed and placed ponds in watersheds with animal agriculture would attenuate downstream fluxes of fecal bacteria. We measured concentrations and fluxes of fecal indicator bacteria (commensal Escherichia coli and fecal enterococci) and manure pathogens (Salmonella and E. coli 0157:H7) in in- and outflows of Bishop Pond in the Southern Piedmont of Georgia during three storm events and in- and outflow concentrations and fluxes of fecal indicator bacteria at Ponds A and C in the Coastal Plain of Georgia during two storm events. Mean concentrations and fluxes of fecal indicator bacteria associated with pond in- and outflow during hydrograph rise, peak, fall, and 5-days after peak flow at Bishop Pond were significantly greater than their mean base flow concentrations and fluxes. In storm flow Bishop Pond significantly reduced the outflow concentrations and fluxes of fecal indicator bacteria compared with corresponding inflow measurements. Unlike fecal indicator bacteria, Bishop Pond appeared not to reduce outflow concentrations and fluxes of Salmonella or E. coli 0157:H7. At Ponds A and C in the Coastal Plain mean in- and outflow concentrations and fluxes of the fecal indicator bacteria associated with the hydrograph rise and peak flows of the storms were not different. Bishop Pond, with a length to width ratio of 3.3, attenuated downstream fluxes of fecal bacteria. In contrast, Ponds A and C were not effective at reducing downstream fluxes of fecal bacteria under storm flow conditions. The ineffectiveness of Ponds A and C may be attributed to their having length to width ratios of 1.2 and 2.5, respectively, both of which are below the minimum for effective pond performance. Our results indicated that in the humid Southeast an appropriately placed and configured pond in watersheds with animal agriculture can reduce storm flow loads of fecal indicator bacteria but not necessarily pathogenic E. coli 0157:H7.

Georgia farmers are increasing preemergence applications of soil residual herbicides to control glyphosate resistant weeds. To improve efficacy these herbicides are often activated by post-application irrigation. Broiler litter is commonly applied to fields before these herbicides. The herbicide 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. On replicated 6 m 2 -plots ( n = 3) simulated rainfall was applied for 70 min with composite runoff samples collected every 5 min and analyzed for E. coli and Salmonella spp. Although total runoff volume from the CT plots was significantly greater than from NT plots, no significant differences in total load of E. coli and Salmonella or the 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 log 10 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.

In the Southeastern Coastal Plain (USA) farmers with access to irrigation commonly water in herbicides following their preemergence application to improve efficacy of the herbicide. This practice increases near surface soil water content and may promote increased runoff during subsequent storm events. The objective of our study was to determine differences in P and N runoff from conventional tillage (CT) and no tillage (NT) systems when herbicides were watered into loamy sand Ultisols fertilized with broiler litter. Simulated rain with variable intensity was applied for 70 min with runoff samples collected every 5 min and analyzed for total P and N, PO 4 3− , NH 4 + and NO 3 − . Results indicated the no-tillage treatment lost significantly more PO 4 3− and NH 4 + than the conventional tillage treatment. However, total P and N and NO 3 − runoff losses were significantly less in the no-tillage treatment. The proportion of total P and N leached through NT residues was 5.6% and 22% of the P and N applied as broiler litter, and the proportion of total P and N in runoff was 0.8% and 1.2% of the P and N applied in broiler litter. Overall 3.4 times more N and 2.7 more P were lost in runoff from the CT treatments than for the NT treatments. Reduced tillage was found to reduce N and P losses when combined with watering-in of surface applied broiler litter.