Influence of technical routes and water quality at the drainage outlet

Abstract

The presence of an land drainage network is, beyond its hydraulic interest, an interesting tool for monitoring the dynamics of solutes leaving the plot. This is the work that has been carried out at Arvalis de la Jaillière station since the late 1980s. The improvement of the soil's water status in winter allows for a better regulation of crop yields. Better still, wheat yields are improved by about eight quintals per hectare, thanks to artificial sanitation. Concerning the transfer of solutes, behaviours vary according to the compound studied. Thus, nitrogen is transferred more in drained plots than in undrained plots, where most transformation processes are blocked due to temporary excess water. Phosphorus and most of the plant protection products studied are mainly associated with diffuse transfer by runoff, but also with rapid preferential circulation, induced by the simplification of tillage. In all the cases studied, the establishment of an land drainage network contributes significantly to the reduction of runoff, and therefore to the associated transfers. Moreover, draining means seeking to secure the production system, in particular by optimizing all farming practices, from tillage to input control. All these elements contribute to preserving water quality when leaving agricultural plots.