Runoff losses of norflurazon : effect of runoff timing

Norflurazon was applied (2.24 kg/ha) in 1988 and 1989 to plots that contained subsurface drains 1 m deep. After soybeans were planted, runoff losses of the herbicide were measured each sermon for about 300 days. The 1988-1989 sermon was atypical in that rainfall was insufficient to produce runoff until 171 days after application. From day 171 until day 302, 61 mm of runoff removed 1.5 g/ha (0.07% of application) of herbicide from the plots. In 1989-1990, runoff was measured for 301 days after application. In this period 50.7 g/ha norflurazon (2.3% of the amount applied) was lost from the plots in runoff