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Persistence and Movement of Chlorpyrifos in Sprinkler - Irrigated Soilč

Department of Entomology, Washington State University, Irrigated Agriculture Research and Extension Center, Prosser,
Washington 99350

J. Econ. Entomol. 74: 385 - 388 (1981)
© 1981 Entomological Society of America


The chemical persistence and vertical movement of chlorpyrifos 4EC in a loam soil were compared with respect to time of post-treatment sprinkler irrigation. Irrigation intervals of 0, 2, and 6 days post-treatment, together with a non-irrigated control, were assessed.

Sprinkler irrigation (2 ha - cm of water) immediately after insecticide treatment reduced the dissipation rate of chlorpyrifos compared with delayed irrigation or no irrigation. Chemical persistence was least in non-irrigated plots. Chlorpyrifos dissipation rates were rapid during the 2 weeks after treatment. Thereafter, chlorpyrifos dissipation proceeded more slowly in all plots but relative rates were greater in non-irrigated plots. Vertical movement of the insecticide in the soil after sprinkler irrigation was minimal; greater than 99% of the total chlorpyrifos residue were found in the top 2.5 - cm layer.