Effect of Manure Application Rate and Timing on the Leaching Potential of Antibiotic Resistant Bacteria.

Antibiotics are used in swine production for therapeutic and growth promotion purposes. Because land application is the most common method of disposing of swine lagoon effluent, there exists the potential threat of contaminating the underlying groundwater with antimicrobial-resistant bacteria (ARB) and associated genes.  Our study is centered on gaining improved scientific understanding on the effect of liquid swine manure application rate and timing on soil leaching of ARB and associated genes. We hypothesize that these two management practices – manure application rate and timing – will have significant effects on the leaching potential of ARB and associated genes through soil. Specifically, we applied swine lagoon effluent known to contain ARB through soil columns packed with either a fine sand or loamy sand at two manure application rates and three time intervals (1 day, 1 week, or 3 weeks) between manure application and first rainfall-induced leaching event.