Behavior of Molinate in Paddy and River Water

Abstract

The fate of molinate in surface water of paddies and rivers was investigated in two river systems of Hiroshima Pref. using Mamet^® granules (molinate 8%, symetryne 1.5%, MCPB 0.8%). In the paddy water, the maximum concentration occurred within a day after application of the granules irrespective of the degree of leaking. The half-lives in the heavily leaking paddies fell in with 0.6 day, and the half-lives in the slightly leaking paddies with or without overflowing water fell in with 2.5 or 4.4 days, respectively. In the river water, the maximum concentration was higher and reached later in the river with smaller discharge than in the one with larger discharge. The half-lives in the river with smaller discharge in the average and year of increased discharge by rain fall fell in with 6.6 or 5.4 days respectively, and the half-lives in the river with larger discharge fell in with 1.9 days. Total molinate amount which flowed from paddies into rivers was estimated to be 3-4% of the applied one irrespective of the degree of leaking, precipitation and river discharge.