Performance evaluation of lysimeter experiments for simulating pesticide dissipation in paddy fields. Part 1: Submerged application of granular pesticides

Abstract

Three-year comprehensive experiments were conducted to compare the dissipation patterns of a total of 16 pesticides, including 3 metabolites, as granular formulations applied in lysimeters and paddy fields with two soil types. Analytical concentrations of the target pesticides in paddy water were analyzed using a granular kinetic model consisting of the following parameters: release rate, decrease rate, and dissolved concentration. Results of parameter grouping analyses of the kinetic models showed that 56% of data reproducibility (entire grouping) was obtained between replicates for the lysimeters. In comparisons between the lysimeters and paddy fields, 48% of decrease rates and 34% of release rates were grouped, although significant differences were observed with a nearly 90% difference for dissolved concentrations. These differences might be attributed to the hydrological components such as water management and meteorological covariates in paddy fields, the daily percolation in lysimeters and the adsorption-desorption kinetics between paddy water and soil.

Inverse analysis to estimate site‐specific parameters of a mathematical model for simulating pesticide dissipations in paddy test systems

“…Finally, the datasets of simetryn and molinate in one of the replicates for the lysimeters (LA‐S1 and LV‐S1 plots in a previous study relabeled as LA and LV plots, respectively) and the paddy fields with alluvial and volcanic ash soils (FA and FV plots) were prepared for the inverse analysis. The detailed experimental design and analytical procedure can be found elsewhere …”

“…The applicability of this procedure in the PCPF-1 model is verified by reproducing the dissipation data of granule paddy herbicides obtained from lysimeters and paddy fields under a standard experimental design in Japan. 27,28 Finally, we conduct a case study to improve the current experimental design for a more realistic simulation of the actual condition.…”

Performance evaluation of lysimeter experiments for simulating pesticide dissipation in paddy fields. Part 2: Nursery-box application and foliar application

“…Note that the experiment in 2012 was conducted under a submerged application scenario, and some of the results were reported in the previous report. 1) Table 1 lists the commercial products, their active ingredients, application date, rates, and the theoretical maximum concentration of pesticides (C max ), which was defined as all pesticides were dissolved in paddy water with 5 cm ponding depth. Detailed explanations of the experimental conditions and testplot designs are available in the previous report.…”

“…In our previous report, 1) the performance of the flooded lysimeter (hereafter denoted as lysimeter) was compared with that in the actual paddy field involving the submerged application of granular formulations. The results indicated that the current experimental design of the lysimeter could reproduce nearly 50% of the decrease rate of granular pesticides used under actual paddy field conditions, although significant differences in the maximum concentrations were observed owing to variations in hydrological and meteorological factors.…”

“…The fundamental description of the experiments involving the lysimeters and paddy fields, the analytical methods, and data processing can be found in the previous report. 1) Materials and Methods…”