Controlling weeds in camelina with innovative herbicide-free crop management routes across various environments

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Camelina (Camelina sativa L. Crantz) is a minor oilseed crop identified as a candidate crop for biorefinery in Europe. This crop should therefore meet specific quantitative, qualitative and environmental requirements. Weeds have been identified as a major problem for growing camelina. Weed competition may result in low camelina yields and poor seed oil quality. Herbicide application during the crop cycle is more over often not effective enough and does not match with a sustainable production. This study aimed at assessing the effect of four crop management routes (CMRs) on weed biomass and camelina yields across various environments in northern France. Three spring camelina CMRs without herbicide were specifically designed: one consisted in doubling camelina sowing rate (DD), and two others consisted in intercropping camelina with either barley (CB) or pea (CP). These CMRs were compared with a current chemical weeding-based crop management route (SD). These four CMRs were tested in nine on-farm trials covering two growing seasons and three soil types. Crop and weed biomass were measured at camelina flowering and maturity stages, and crop yields were estimated at harvest. Across the nine environments, crop biomass was significantly higher in both intercrops than in pure stand (SD and DD). Weed biomass varied across CMRs and environments, and was negatively correlated with total crop biomass, thus explaining the better weed control observed in the intercrops. Considering the nine environments, DD and CP did not significantly impact camelina yields in comparison to SD. However, camelina yields were reduced by 90% in CB due to strong competition from barley. In conclusion, both DD and CP seemed to be promising alternatives to reduce weed competition without using herbicides. In the future, multi-criteria assessment covering quality, environment, and economic performances would be useful to conclude on the implementation of these CMRs in on-farm conditions.