Submitted to: American Chemical Society Symposium Series
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 1997
Publication Date: N/A
Technical Abstract: In the deep loess hills along the Missouri River valley of southwestern Iowa, field studies are underway to determine the impact of continuous corn production on surface water quality. Chemical quality of runoff for nitrate-N, atrazine and metolachlor are compared for four field-sized watersheds under different tillage practices. Beneath the snow cover of early March 1993, a diurnal freeze-thaw cycle was observed which resulted in displacement of both nitrate-N and parent herbicides in surface runoff generated by melting snowcover. During the five days of repetitive events, the nitrate-N and the herbicide displacement patterns are different for the conventional, terraced, and ridge-till fields. The effects of topography, tillage, and the kinetics of diffusion and dispersion on the release of both nitrate and herbicide are presented. The minimum total mass of nitrogen and herbicide displaced over the 5 day period is estimated for each field.