ARS | Publication request: Diazinon accumulation and dissipation in Oryza sativa L. following simulated agricultural runoff amendment in flooded rice paddies

Submitted to: Water, Air, and Soil Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 24, 2008
Publication Date: June 15, 2009
Citation: Kroger, R., Moore, M.T., Cooper, C.M., Holland, M.M. 2009. Diazinon accumulation and dissipation in Oryza sativa L. following simulated agricultural runoff amendment in flooded rice paddies. Water, Air and Soil Pollution 201:209-218.

Interpretive Summary: In late fall and early winter, pesticide runoff from certain crops (i.e. stone fruits)poses a potential risk to downstream aquatic receiving systems such as rivers or lakes. This time frame also coincides with rice fields lying dormant post-harvest with organic residue remaining in the production acreage. An experiment was conducted to determine the degradation of an organophosphate insecticide on dead / dying plant material over a period of four months. Samples of plant materials in decomposition bags over the study duration indicated rice plants were effective at adsorbing the insecticide and preventing it from leaching back out to the water for possible contamination.

Technical Abstract: Flooded post-harvest rice paddies were examined as potential best management practices for reducing diazinon (organophosphate insecticide) concentrations in stormwater runoff. Two rice paddies were cultivated in Oryza sativa L. and amended with a 3hr, 0.1% simulated stormwater diazinon runoff event. Initial diazinon adsorption peaked at 347 'g kg-1 and 571 'g kg-1 mean rice aboveground plant tissue concentrations for each pond respectively. Subsequent senescence of aboveground tissue showed significant decreases in tissue mass (r2 = 0.985) and adsorbed diazinon mass (90±4% and 82±1%) within one month of amendment, with no corollary increases in water column diazinon concentration. Diazinon was below detection in all aboveground tissue samples from either rice ponds three months post application. This study shows the relative effectiveness of diazinon adsorption by post-harvest rice plants and a potential mitigation strategy of senescence and pesticide degradation for contaminated tailwater.