Evaluation of the management practice for controlling herbicide runoff from paddy fields using intermittent and spillover-irrigation schemes |
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| Authors: | Hirozumi Watanabe Youji Kakegawa Son Hong Vu |
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| Institution: | (1) Tokyo University of Agriculture and Technology, 3-5-8, Saiwaicho, Fuchu Tokyo, 183-8509, Japan |
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| Abstract: | Two water management practices, an intermittent irrigation scheme using automatic irrigation system (AI) and a spillover-irrigation
scheme (SI), were compared for the fate and transport of commonly used herbicides, mefenacet (MF) and bensulfuron-methyl (BSM)
in experimental paddy plots. Maximum mefenacet concentrations in paddy water were 660 and 540 μg L−1 for AI and SI plot, respectively. The corresponding values for bensulfuron-methyl were 46.0 and 42.0 μg L−1. Dissipation of the herbicides in paddy water appeared to follow the first-order kinetics with half-lives (DT50) of 1.9–4.5 days and DT90 (90% mass dissipation) of 7.8–11.3 days. The AI plot had no surface drainage, hence no herbicide was lost through paddy-water
discharge. However, SI plot lost about 38 and 49% of applied mefenacet and bensulfuron-methyl, respectively. The intermittent
irrigation scheme using automatic irrigation system with a high drainage gate was recommended to be a best management practice
for controlling the herbicide losses from paddy fields. The paddy field managed by spillover-irrigation scheme may cause significant
water and herbicide losses depending on the volume of irrigation and precipitation. The water holding period after herbicide
application was suggested to be at least 10 days according to the DT90 index. |
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| Keywords: | Herbicide loss Water management practice Water holding period Mefenacet Bensulfuron-methyl |
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