Grass weed management: what levers are used by growers?

The GRAMICOMBI project was launched as part of the PARSADA program. Spearheaded by Terres Inovia, its aim is to develop combinations of levers for integrated grass weed management and to deploy them on a national scale.

To find out what hinders the adoption of agronomic levers for better grass weed management, a survey was carried out among farmers. " It was carried out as part of the Objectif Cultures Propres (OCP) network in Bourgogne Franche Comté, which aims to assess the effectiveness and feasibility of combining grass management levers at the cropping system level, by monitoring and implementing an action plan for five years on 32 farmers' plots ", explains Victor Fleury, development engineer at Terres Inovia. The network is run by nine partners: Terres Inovia, Arvalis, Alliance BFC, the departmental Chambers of Agriculture of the BFC region and the Tart-le-Bas experimental farm.

During the survey, each farmer ranked different grass management levers, according to their feasibility, in one of four categories: achievable, possible, restrictive and impossible.

The results show a high degree of heterogeneity in the adoption of levers. " Some practices are already well integrated into cropping systems, such as the application of glyphosate before sowing, diversification of chemical weed control and border maintenance ". On the other hand, some levers are less widely used, despite their recognized agronomic value: the combination of staggered sowing dates, diversification with mechanical weeding and cleaning of harvesting tools offers considerable scope for progress. Lastly, others, such as the introduction of an Intermediate Energy Crop (CIVE), pollarding and the recovery of chaff, are generally perceived as difficult to integrate into current systems.

The main obstacles are economic: access to specific equipment, lack of outlets, investment costs and uncertain profitability. The adoption of new grass weed management levers also comes up against technical trade-offs: ploughing, for example, is often seen as a lever of last resort in the event of technical impasse. Similarly, the choice of variety is often prioritized for disease resistance or yield potential, to the detriment of covering power. " The lack of technical references, consensus on the effectiveness of certain levers and feedback from experience also hinders their adoption. The example of covering varieties is a good illustration of this difficulty, with effectiveness perceived as highly variable depending on the context ". Finally, certain obstacles are very specific: working time and site organization for mechanical weeding, recourse to service provision, soil type, plot distribution, etc.

The survey results show that many grass weed management levers are still under-utilized by farmers. While some are hampered by structural or economic obstacles, others require technical support for the farmer, reinforced references and adaptation to the context of each farm. This is precisely the aim of the PARSADA GRAMICOMBI project, led by Terres Inovia, which includes the OCP network: to remove the barriers to adoption and promote a coherent combination of grass weed management levers across the entire cropping system.