Leaching losses of norflurazon through Mississippi River alluvial soil

The pre-emergence weedkiller, norflurazon (4-chloro-5-(methylamino)-2-(3-trifluoromethyl)-phenyl-3(2H)-pyrid a zi none), is widely used in Louisiana for the control of broadleaf of weeds. Results are reported from studies on the leaching of this compound in subsurface-drained plots on alluvial soil. The concentrations of the weedkiller in the top 15 cm of the soil at various periods after application in 2 successive years are tabulated and the concentrations in subsurface drains and cumulative losses in drains are presented in graphs. The results from the present study and from a previous study on leaching of atrazine are summarized in a table and discussed in relation to the difference in rainfall in different years. Soil leaching of norflurazon could be an important pathway for disappearance of this chemical.