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Fig. 9. Maps of the Morgan Creek watershed showing the total mass of metolachlor and metabolites applied or produced, transformed, leached, and residual in the unsaturated zone as of October 2004. A total of five corn-soybean rotations from 1995 through 2004 are simulated. All areas with corn–soybean rotation received a loading of 1.36 kg ha–1 of metolachlor preceding the corn crops. This resulted in a total load of 6.8 kg ha–1 for the 10 yr except for the intensive study field which received only four applications for a total of 5.44 kg ha–1. The pattern shows the location of corn and soybean fields, with greater leaching in areas with thinner unsaturated zones, and also greater residuals for areas that were in corn in 2004. Units are kg ha–1. White areas indicate values of zero.
