Modelling the transfer of 2 herbicides in drained clay soil over a 10-year period
Résumé
The ability of the pesticide leaching model MACRO to predict the transfer of isoproturon (IPU) and diflufenican (DFF) to drains was evaluated using data originating from La Jaillière in Western France. The dataset comprises 10 years of monitoring data for drainage and runoff volumes of water and associated pesticide concentrations under typical agricultural practice. The model was parameterised on the basis of information on particle size distribution, organic matter content and the structure of the soil. Batch experiments were also undertaken to establish the sorption characteristics of the soil horizons. A key objective of the work was to assess the performance of MACRO without resorting to significant calibration. The magnitude as well as the timing of water fluxes and the transfer of isoproturon were adequately simulated by the model. The fact that such good fits can be obtained without any calibration is rare. Initial runs for diflufenican resulted in an underestimation of transfers, but this could be addressed by using literature values for sorption as opposed to on-site measurements. Implications for the development of national scenarios for surface waters in France will be discussed.