Simulation of mefenacet concentrations in paddy fields by an improved PCPF‐1 model

Abstract

An improved simulation model (PCPF-1) has been evaluated for the prediction of the fate of mefenacet in an experimental paddy field. This model simulates the fate and transport of pesticide in paddy water and the top 1 cm of paddy soil. Observed concentrations of mefenacet in the paddy water and the surface soil exponentially decreased from their maximum concentrations of 0.70 mg litre(-1) and 11.3 mg kg(-1), respectively. Predicted mefenacet concentrations both in the water and surface soil were in excellent agreement with those measured during the first 2 weeks after herbicide application, but concentrations in paddy water were appreciably overestimated thereafter. The model simulated mefenacet losses through runoff, percolation and degradation to be respectively 41.9%, 6.4% and 57.3% of applied, and the mass balance error was about -6%. The model simulation implied that drainage and seepage control, especially shortly after application when herbicide concentrations are high, is essential for preventing pesticide losses from paddy fields. In focusing on pesticide concentrations in this early period the PCPF-1 model can be a beneficial tool for risk assessment of pesticide losses and in the evaluation of agricultural management for reducing pesticide pollution associated with paddy rice production.

Behavior of nursery-box-applied imidacloprid in micro paddy lysimeter

“…Pesticide fate and transport in the water-soil system in a paddy eld is subjected to pesticide desorption from paddy soil, and the adsorption and degradation of pesticides, as well as water management, which greatly in uence pesticide dissipation. 43) A limitation of MPL is its small scale. ere are only 4 rice plants per MPL, which may cause errors in the applied mass of pesticide; thus, the pesticide should be weighed with care.…”

Herbicide discharge from rice paddy fields by surface runoff and percolation flow: A case study in paddy fields in the Lake Biwa basin, Japan

“…At this plot, the surface runoff flow rate was second highest (0.11 L/s); however, the herbicide was applied 2 days prior, and the concentration in the paddy water was estimated to be high. Previous studies 15,19,25) show large pesticide losses result from spillover irrigation management. The current study indicates that surface runoff from even a single paddy plot with not only a large amount of water flow but also flow over an especially short duration after application has the potential to significantly affect pesticide discharge from the watershed.…”

“…The other is percolation flow caused by deep percolation and lateral seepage through bunds. Previous reports 5,[20][21][22][23] of field observations and model simulations 15,19,22,24,25) revealed that surface runoff, especially that which occurred a few days after pesticide application, is responsible for a significant amount of pesticide discharge from paddy fields because of the high concentrations of pesticides in paddy water. Based on this information, spillover water management has been recognized as an inappropriate farm practice.…”

“…In field-monitoring studies of rivers [2][3][4][5][6][7][8][9][10] and lakes, [11][12][13] pesticides commonly used in rice paddy plots during the cultivation period have been detected frequently. In addition to field observations, simulation models such as PADDY [14][15][16] (Pesticide Paddy Field Model) and PCPF-1 [17][18][19] (The Pesticide Concentration in a Paddy Field model) were developed in Japan to assess and manage the potential environmental risks associated with pesticide discharge from paddy fields.…”

Effects of insecticides on aquatic ecosystems in Bangladesh

“…To investigate the relevance of the pesticide exposure caused via water runoff events during the rice-growing season we parameterised the PEARL model (Leistra et al, 2001) which was modified for applications in (flooded) paddy rice according to Ter Horst et al (2014). Although other models simulating pesticide fate in paddy rice exist (MED- Rice, 2003;Karpouzas et al, 2006;Inao et al, 2008;Inao and Kitamura, 1999;Watanabe et al, 2006;Young, 2012) the PEARL model was selected because it is a field scale model that simulates the runoff and pesticide concentrations in the runoff. Furthermore, the model is freely available and allows calibration without an extensive dataset being available (Ter Horst et al, 2014).…”