TILE DRAINAGE MANAGEMENT INFLUENCES ON NUTRIENT, BACTERIA, AND VETERINARY ANTIBIOTIC MOVEMENT TO GROUNDWATER AND SURFACE WATER FOLLOWING LIQUID MANURE APPLICATION

Agricultural tile drainage systems are known to be significant sources of surface water contamination within intensively farmed regions such as Southern Ontario and the US Midwest. Tile drainage management, or controlled tile drainage (CD), is a beneficial management practice that is gaining popularity because of its ability to mitigate off-field losses of potential surface water contaminants, and to retain nutrients within the soil profile. In this presentation, we will look at the results from a set of field and modelling experiments that were designed to assess the efficacy of CD for reducing the movement of liquid swine manure constituents, which included nutrients, indicator and pathogenic bacteria, veterinary antibiotics, and tetracycline resistant genes, to surface water following manure application on a macroporous clay loam soil. To aid with the characterization of the flow and transport processes, rhodamine WT was used as an additional chemical tracer and monitored in both the tile effluent and shallow groundwater with relatively high temporal resolution. Results from this work give a detailed assessment of the impact that tile drain effluent can have on surface water quality in agricultural watersheds, and on the ability of CD to reduce these potential impacts.