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RESEARCH PRODUCT

Highlighting the role of diversity in driving weed dynamics and weed-crop interactions

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EAGESTAD INRA; Weeds are responsible for crop losses and their management, mainly through herbicide applications, has led to resistances and environmental impacts. Integrated Weed Management encourages the use of “many little hammers” such as crop rotation, mechanical weeding, stale seedbed technique and delayed sowing … i.e. more complex and diversified cropping systems, in order to increase cropping system sustainability. However, research is still required to test the effectiveness of combinations of these alternative tactics in a wide range of agricultural contexts. Furthermore, the cropping system approach considers all these individual hammers, whose effects on agricultural weeds have been studied separately, as a coherent whole. This provides a unique framework to study how a meaningful set of agricultural practices impacts weed community assembly, i.e. what are the traits that allow species to persist in IWM cropping systems? Moreover, we can expect that a greater diversity of agricultural practices will lead to a greater diversity of weed species and weed traits. This brings into question: what are the beneficial aspects of more diversified weed communities? Can we expect them to limit yield losses? Is the demography of diversified weed communities more stable in time? These are the different research questions I will try to tackle during the next three years through the analysis of a diversity of datasets (23 year old factorial experiment in Pisa, 16 and 6 year old cropping system experiment in Dijon and Toulouse, a “O pesticide” network of cropping system experiments in 8 sites in France and a field experiment aiming to monitor the evolution of the weed/(weed+crop) biomass ratio during the cropping season in a variety of weed contexts). The final objective is to design cropping systems whom maintain yield potential and weed diversity while minimizing negative environmental impacts.