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RESEARCH PRODUCT

Strategic tillage in Conservation Agriculture : consequences on weed communities and winter wheat productivity

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In Europe, Conservation Agriculture is currently challenged by higher weed pressure, potential glyphosate ban andreduced crop yield. The introduction of strategic tillage could be a viable option to diversify selection pressures onweeds and increase crop yield. Three types of fallow management (ploughing (CT), reduced tillage (RT), no-till withglyphosate (NT)) were compared on four fields after 17 years of no-plough, which ended with 7 years of NT. Weeddensity, weed composition, crop productivity and yield components were assessed in the following winter wheat.The reintegration of tillage after 17 years of Conservation Agriculture proved to be a major driver of weed communities before weeding (density, richness and composition). Weed density and species richness before weeding wasgreatest in RT, intermediate in CT and lowest in NT. Density of Alopecurus myosuroides, the most problematic weedof the experiment was higher in RT than in CT or NT. Differences in weed community composition were discussedin terms of weed seed longevity and weed seed movements associated to RT and CT. The number of grains perear and crop yield increased with tillage intensity (+11% for RT, +31% for CT). Specific weight and protein contentwere not affected by tillage treatments. Differences in winter wheat productivity were possibly related to enhancedsoil structure and increased mineralization of soil organic matter. Strategic ploughing could be a viable solutionto manage herbicide-resistant weeds in no-till cropping systems. Potential benefits will depend on the density andcomposition of the newly upwelled weed seedbank.