Leaching of Post-Emergence Herbicides into Shallow Groundwater during Transition from Conventional Tillage to No-Tillage on Des Moines Lobe Soils of Central Iowa

摘要

In a four-year field study carried out on a 96-ha field, we have evaluated the impact on shallow groundwater quality of transition from conventional-till to no-till for two herbicides now commonly used in minimum-till corn/soybean systems. Nicosulfuron and imazethapyr were studies. Well water samples were obtained from shallow piezometers using manual bailers and residue analyses carried out in our laboratory. Methods utilized SPE cartridge chemistry followed by HPLC/MS/MS techniques. providing a 10 part per-trillion quantitation limit in two-liters of filtered groundwater. By January of 1993, ten months following initial application, imazethapyr, nicosulfuron, and one nicosulfuron degradate had been detected in the well water and confirmed by MS/MS. During the 1993 through 1995 sampling seasons, average concentration in the piezometer samples was 131 and 125 part-per-trillion for nicosulfuron and imazethapyr, respectively. The data show that these widely used ALS-inhibiting chemicals are capable of leaching to shallow groundwater during tillage transition.