Chapter 13 Mobility and Dissipation of Clopyralid Herbicide in Turfgrass Field Lysimeters

摘要

The mobility and dissipation of clopyralid herbicide was studied in undisturbed soil monoliths (lysimeters) on Long Island, NY, June through October, 2000. Clopyralid was applied at a rate of 280 g acid equivalent (ae) per hectare to lysimeters containing undisturbed sand, considered highly vulnerable to leaching, with turfgrass cover. Bromide (Br) was applied to track water movement. Natural rainfall was supplemented weekly with sprinkler irrigation to achieve at least 130% of normal precipitation. Downward movement of clopyralid was limited to the upper 15-cm soil profile, dissipating rapidly in soil with a first-order field half-life of 9 days. For the entire 4-month study period, clopyralid was undetected (detection limit 0.4 ppb) in leachate even after rainfall plus irrigation totaled 552 mm or 173% of normal. Cumulative leachate volume totaled 310 mm, or 56% of on-site rainfall plus irrigation, and bromide tracer breakthrough was well established. Although some physico-chemical properties of clopyralid are characteristic of pesticides having a potential to leach, this study demonstrated that leaching potential in the field, under turfgrass use conditions, is extremely low, being offset by plant interception, rapid soil degradation and/or increased soil sorption with increased residence time.