Date of this Version
Research Report. Public Heath/Worker Safety. NPB #12-012
The objective of this study was to determine the effects of narrow grass hedges on the fate and transport of antimicrobials and antimicrobial resistance genes (ARGs) in runoff and in soil following the land application of swine manure slurry. Swine manure slurry was land applied to 0.75m wide by 4.0m long plots established on an Aksarben silty clay loam soil located in southeast Nebraska. Swine manure was applied at a rate to meet the 3-year nitrogen (N) requirements for corn. Swine manure was applied to plots with and without a narrow grass hedge to evaluate the effect of the hedge on antmicrobial and ARG occurrence in runoff following 3 30-min simulated rainfall events. The grass hedge proved to be consistently effective in reducing concentrations of the antimicrobial tylosin in runoff (p=0.016), and the total mass of tylosin transport in the runoff was reduced by an order of magnitude in plots with the grass hedge compared to plots without the grass hedge. Because we did not observe significant differences in the total amount of runoff between plots, we can attribute the reduction in mass loading to the decrease in tylosin concentration in plots with the grass hedge. The results of the grass hedge on removal of ARGs in runoff was less clear cut. The effect of the grass hedge on removal of erm(B) was not statistically significant (p=0.2465), however, the grass hedge did significantly reduce the amount of 16S rRNA in the runoff. rANOVA results suggest that the narrow grass hedge had a significant effect on removal of microbial genes in runoff (p – 0.0014). To our knowledge, this is the first effort to evaluate the effect of common and low cost best management practices such as narrow grass hedges on the transport of microbial genes in runoff.