Submitted to: Symposium on the Fate and Chemistry of Modern Pesticides Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 22, 2008
Publication Date: October 22, 2008
Citation: Koskinen, W.C., Papiernik, S.K., Yates, S.R., Barber, B.L. 2008. Metolachlor Dissipation Following Fall and Spring Application to Eroded and Rehabilitated Landscapes of the US Corn Belt. Symposium on the Fate and Chemistry of Modern Pesticides Proceedings. October 22-25, 2008. Marseille, France. p. 73. Technical Abstract: A study was conducted to evaluate the effects of landscape position and soil properties on the rate of metolachlor dissipation and weed control efficacy of fall- and spring-applied metolachlor in eroded and rehabilitated landforms in the midwestern United States. Soil-landscape rehabilitation resulted in large changes in surface soil properties, i.e. surface soil organic carbon contents in upper slope positions averaged 14 g/kg in unrestored plots and 35 g/kg in restored plots, however the rate of metolachlor dissipation in the top 1 m of soil was not drastically different in rehabilitated and undisturbed plots. There was little degradation of fall-applied metolachlor during the first two weeks after application. Samples collected the following spring showed that, averaged over the entire site, < 20% of the applied metolachlor still remained in the root zone during emergence and early crop growth. Similar results were observed for the bromide tracer. In contrast, 30-40% of the spring-applied metolachlor remained in the root zone 3 to 7 weeks after application. It appears that in contrast to springapplied chemical, fall-applied metolachlor may have been transported out of the root zone resulting in poor weed control and increased potential for contamination of surface and ground waters. Our results suggest that metolachlor should not be fall applied in the northern Corn Belt of the United States.