The management of underground water resources and their contamination is a significant factor in the supply of good quality drinkable water. Since groundwater contamination only becomes visible after many years, it is essential to anticipate the flow of plant protection products (PPPs) capable of reaching it. For this reason, since 2006, the maximum permissible concentrations of pesticides in groundwater are equivalent to those set for drinking water, i.e. 100 ng.L-1 per substance and 500 ng.L -1 for total substances.
The originality of the SolPhyLy project is based on the use of lysimeters. Our own devices are 1.5-metre high, 1-metre diameter, soil-filled stainless steel cylinders buried 50 cm deep in agricultural plots. These recover the water that seeps through to a depth of 2 metres. This makes it possible to determine the flow of pesticides passing through the soil and reaching the groundwater. It is believed that, below a depth of 1 metre, these compounds are no longer broken down by the soil and will therefore reach the groundwater sooner or later.
The project thus helps improve our understanding of the decomposition of PPPs in the soil, both in actual field conditions and in various farming practices (whether or not these involve ploughing, restitution of crop residues etc.), as well as flows towards underground waters. It also offers an alternative to the use of glyphosate.
SolPhyLy is a three-year project that was launched during the 2018-2019 season. During this first year, extensive work has been done on refining methods that enable the analysis of 39 soil pesticides and 61 water pesticides and metabolites. An experiment dedicated to the search for alternatives to chemical weed control in cereals has also been implemented by Gembloux Agro-Bio Tech.
Although they are provisional and were obtained within the context of the 2018 drought, the results recorded so far show concordance between the treatments performed and the residues observed in soil and water, thus confirming the relevance of the lysimetric tool in the observation of PPP flows and, where applicable, in the prevention of groundwater contamination.
This multidisciplinary project is funded by the Wallonia Public Service (DGO3) and is the result of a collaboration between the CRA-W and Gembloux Agro-Bio Tech "Sol" and "Phytotechnie"
Further information on this project can be found on: https://www.cra.wallonie.be/fr/sol-phy-ly