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Preferential flow has been identified as a major contributor to the rapid and unexpected transport of agricultural chemicals to groundwater. Unfortunately, the scope and magnitude of preferential flow, as well as its impact on and relevance to field-scale contaminant transport, have not been quantified and resolved. These limitations were, in large part, due to conventional sampling protocols which are inappropriate for measuring the impact of soil processes that are highly dynamic in both spatial and temporal domains. A method using tile drains was developed which allows subsurface fluxes of surface applied solutes to be accurately determined. Since larger pores may become hydraulically active as the soil profile becomes wetter, the impact of preferential flow paths on contaminant transport may be strongly influenced by rain intensity and duration. This presentation will use data collected from tile drain experiments to demonstrate the relevance and impact of agricultural management, specifically irrigation on preferential fluid dynamics.