Antibiotics Losses from Swine Manure Application on Tile Drained Soils

Since their discovery, antibiotics have been instrumental in treating infectious diseases that were previously known to kill humans and animals. However, their widespread use as animal feed additive has raised concerns about the contamination of water and food supplies as well as in the emergence of antibiotic-resistant microorganisms. As much as 80% of the antibiotics added in animal feed may be excreted in urine or manure. Once excreted, these antibiotics can enter surface and/or ground waters through non-point source pollution from manure-applied fields. This study quantified antibiotics losses in runoff and drainage from swine manure application on a tile drained Webster clay loam. The experiment was a randomized split-plot design with four replications. The main plots were two primary tillage treatments (fall moldboard plowing versus chisel plowing) and the sub-plots were two nutrient sources (fall injected liquid swine manure versus spring-applied urea). At recommended N application rate, chlortetracycline and tylosin applications rates were 229 g/ha and 256 g/ha in 2001; and 199 g/ha and 165 g/ha in 2002. Field studies showed very little transport of dissolved chlortetracycline and tylosin through Webster soil into tile drains. There was almost no transport of dissolved chlortetracycline in surface runoff. Only about 0.07% of the applied tylosin was transported as dissolved tylosin in surface runoff. Soil analysis showed that most of the manure-applied antibiotics remained in place but there was some off-site transport of these antibiotics with sediment. Batch and flow through adsorption studies showed these two antibiotics are tightly adsorbed by soils. X-ray diffraction analysis showed chlortetracycline adsorption in the clay lattice as compared to surface adsorption of tylosin. The paper discusses the implications of these results for land application of antibiotic laden swine manure on tile drained clay soils.