Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 23, 1999
Publication Date: N/A
Technical Abstract: Groundwater quality changes attendant to the transition from deep disking to no-till were evaluated by monitoring well water chemistry for residues of the post-emergent grass herbicides, nicosulfuron and imazethapyr. The "leaching potential" of these chemicals on a glacial till soil was studied on a 120-ha tile-drained field farmed as a split corn/soybean rotation. Each year, nicosulfuron (ACCENT) was applied to the corn acreage and imazethapyr (PURSUIT) to the soybean acreage, both at the recommended label rate. Paired wells were installed at fourteen locations distributed across the field relative to landscape position and soil association. Each pair was screened at 6-12 ft depth, above and below the nearest tile line. During 1993-1994, monthly samples were collected between April-October. Residue analysis for nicosulfuron and imazethapyr involved cartridge extraction of an acidified water sample, followed by HPLC separation. Identification was by retention time matching and quantitation by electrospray MS using the M+H ion for multi-point calibration.