Gérer les adventices sans travail du sol ni herbicides n'est pas possible dans les systèmes de grande culture.

The aim of this study was to investigate the links between reduced tillage, reduced herbicide use and eeds with surveys and simulations with the FLORSYS model. In the 395 cropping systems identified during farm surveys the herbicide treatment frequency index increased when the frequency of tillage decreased. The simulations showed that eliminating tillage without any other change in management practices doubled the yield loss due to weeds. We identified (1) which weed traits increased when tillage was deleted, (2) which cropping systems were robust to tillage deletion, and (3) which management techniques were associated with a reduction in tillage, in herbicides, and in yield loss. No no-till herbicidefree system was able to reduce yield loss. This simulation study confirms that two pillars of Conservation Agriculture (diversified rotations, permanent soil cover) must be respected to manage weeds in systems that reduced both tillage and herbicides.