かけ流し灌漑水田からの農薬排出量の削減

概要

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Two methods for reducing the amounts of pesticides discharged from continuously irrigated rice paddies were evaluated by molinate and simetryn. The first method used a secondary outlet installed near the irrigation water inlet on the short side of an experimental paddy (0.5ha). The original outlet on the opposite side of the inlet was closed and pesticides were applied. Runoff from the secondary outlet began 1.25 hours after irrigation (1.7l·sec-1) starting, and the pesticide concentrations were measured at the secondary outlet as well as around the midpoint of the long side of the paddy. The loads from the secondary outlet were 0.114g·ha-1 of molinate and 0.035g·ha-1 of simetryn, whereas the loads from the original outlet were estimated from the concentrations at the midpoint to be 5.48 and 1.44g·ha-1, respectively, that is, a 98% reduction in the pesticide runoff load. In the second method, an experimental paddy (0.07ha) was irrigated for four days with 0.63l·sec-1 after pesticides application. The drainage from this paddy was discharged through a secondary paddy (0.08ha). The inflows of molinate and simetryn to the secondary paddy were 477 and 83.0g·ha-1, and the outflows were reduced to 257 and 32.8g·ha-1, respectively.
社団法人　日本水環境学会の論文
2007-11-10