Performance evaluation of lysimeter experiments for simulating pesticide dissipation in paddy fields. Part 2:...

Comparative experiments investigating the dissipation of four nursery-box-applied pesticides and three foliar-applied pesticides were conducted using lysimeters and in actual paddy fields. In the lysimeter experiments, there were test plots for submerged application for both application types. Analytical concentrations of the pesticides in paddy water were evaluated using appropriate kinetic models. The detection levels of pesticides in the paddy water for the nursery-box and foliar applications were 10-77% and 42-79% of the submerged application, respectively. The times required for 50% dissipation (DT ₅₀s) in case of the nursery-box and foliar applications were 0.8-10.4 days and 0.5-2.7 days, respectively. Although overall dissipations were affected by the physicochemical properties of the pesticide and the experimental design in the test plots, the initial detection levels in the lysimeters, governed by the runoff at transplanting and the deposition at spraying, were comparable with those in the actual paddy fields.