Response of runoff diazinon concentration to formulation and post-application irrigation

Evans, J.R.; Edwards, D.R.; Workman, S.R.; Williams, R.M.

Response of runoff diazinon concentration to formulation and post-application irrigation

1998

Evans, J.R. | Edwards, D.R. | Workman, S.R. | Williams, R.M.

Pesticides used in urban environments can be transported in runoff to downstream waters and cause adverse environmental consequences. This experiment assessed the effects of post-application irrigation depth (0, 6.4, and 12.7 mm) and formulation (liquid and granular) on concentration and transport of diazinon (a pesticide commonly used for lawn insect control) in runoff from "tall" fescue (Festuca arundinacea Schreb.) plots. The post-application irrigation was applied using rainfall simulators immediately following diazinon application. The rainfall simulators were again used approximately 2 h after diazinon application to apply the equivalent of a heavy rainfall (64 mm/h for approximately 1.5 h) to generate runoff. Runoff was sampled and analyzed for diazinon using the enzyme-linked immuno-sorbent assay method. Post-application irrigation depth had no effect on diazinon concentration but increased diazinon mass transported off the plot by increasing plot runoff Flow-weighted mean runoff diazinon concentration for the liquid formulation of diazinon was roughly double that of the granular formulation (0.59 vs 0.29 mg/L), attributed to the higher solubility of the liquid formulation relative to the granular formulation. The results indicate that post-application irrigation can increase runoff losses of diazinon for heavy rainfall occurring soon after application, but that these losses can be reduced by use of the granular formulation.

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