Measurement and modelling of water flows and pesticide leaching under low input cropping systems

16 páginas, 7 tablas, 1 figura

One current challenge in sustainable agriculture is to redesign cropping systems to reduce the use and impacts of pesticides, and by doing so protect the environment, in particular groundwater, and human health. As a large range of systems could be explored and a wide number of pesticides used, field experiments cannot be carried out to study the sustainability of each of them. Thus, the objectives of this work were (1) to measure water flows and pesticide leaching in six contrasted low input cropping systems based on sunflower-wheat rotation, oilseed rape-wheat-barley rotation, and maize monoculture, experimented for three years in three different soil and climatic conditions, and (2) to assess and to compare the ability of three pesticide fate models (MACRO, PEARL, PRZM) to simulate the observed water flows and pesticide concentrations. The systems were designed using various crop rotations, including cover crops and intercrops. The models were parameterized with generic parameter estimation routines as done for regulatory risk assessment, and a method was developed to parameterize intercrops, not represented in the models: the use of average crop factors, maximum LAI, crop height and rooting depth of the crops constituting the intercrop allowed acceptable simulations of cumulative water flows, but not their dynamic. Twelve pesticides of 70 applied were quantified in lysimeter samples (e.g. bentazone, glyphosate, S-metolachlor), and their concentrations exceeded 0.1 μg L-1 in several occasions. The performance of the models to reproduce pesticide concentrations was generally poor illustrating the great challenge and the progress needed to simulate accurately pesticide transfers into the soil. The best fits to measured data were attained using "worst-case" pesticide sorption and degradation parameters. Overall, MACRO performed better than PEARL and PRZM. The method developed to parameterize intercrops could be used for risk assessment of groundwater contamination by pesticides in low input cropping systems, but the use of the three models without any calibration is likely to underestimate pesticide leaching in several situations.

The authors are grateful to Pascal Farcy (INRAE, Unité Expérimental d'Epoisse (U2E), Bretenière), Simon Giuliano, Gael Rametti and François Perdrieux (INP-EI Purpan – UMR 1248 AGIR, Lamothe), and Arnaud Coffin and Frédéric Lombard (Agroécologie, INRAE, Institut Agro, Univ. Bourgogne, Univ. Bourgogne Franche Comté) for providing field experimental data. They are also very grateful to Dr. Nick Jarvis (Swedish University of Agricultural Sciences) for his contribution to the development of the unofficial release of MACRO. This project was supported by the research program “For the Ecophyto plan (PSPE1)” funded by the French Ministry in Charge of Agriculture (Perform project), by the research program “Assessing and reducing environmental risks from plant protection products” funded by the French Ministries in charge of Ecology and Agriculture (Ecopest project), and by the research program “Multi-criteria evaluation and quantitative modelling of low pesticideuse systems in multi-site networks” of the French Ministry in Charge of Agriculture funded by ONEMA (System-Eco-Puissance4 project).

Peer reviewed