Modeling Pesticide Transport Via Subsurface Drainage Under Different Tillage and Application Rates At Nashua Iowa Using RZWQM.

Pesticide transport from agricultural fields via runoff and subsurface drainage are mutually dependant processes. Conservation tillage can reduce pesticide loss via runoff but can increase pesticide transport via subsurface drainage. The ability to accurately model pesticide transport in subsurface drainage under different conditions and tillage practices would improve our understanding of the effects of conservation practices on both chemical and biological transport (e.g., pesticides, pharmaceuticals, E. coli). Furthermore, the use of well tested models would help with designing the most effective systems to protect the environment. A well cited recent review article suggests that the effects of tillage on pesticide losses via drainage and leaching are insufficiently known and unpredictable (Reichenberger et al., 2007). However, recommendations have been published concerning the use of the Root Zone Water Quality Model (RZWQM) to simulate pesticide leaching under different tillage conditions. Our objectives are to test RZWQM using 6 years of atrazine data from fields with subsurface drainage near Nashua Iowa under several different treatments. These monitored field plots include different rates of atrazine application along with both no-till and moldboard plow treatments. Preliminary results suggest that RZWQM accurately simulates atrazine concentrations in subsurface drainage at Nashua Iowa.