-Mixing plant species in agroecosystems is highlighted as an agroecological solution to reduce pesticides and fertilizers while maintaining profitability. In the French context, intercropping frost-sensitive legume crops with winter oilseed rape is potentially interesting and began to be implemented by farmers. In this study we aimed at measuring the services and disservices of this intercrop with three different legume mixtures, in terms of growth and yield for rapeseed, ground cover of weeds in autumn and damage caused by rape winter stem weevil. The experiment was carried out at four sites from 2011 to 2014. We showed higher total aerial dry weights and total aerial nitrogen contents in the intercrops compared to sole winter oilseed rape in November. The companion plants contributed to the control of weeds and the mitigation of rape winter stem weevil damage, notably through the increase in the total aerial weight. In spring, after destruction of the companion plants, the intercrops had partially compensated a reduction in the N fertilization rate (-30 kg per hectare) in terms of aerial nitrogen content in rapeseed, with no consequences on the yield which was maintained or even increased. There were probably other interactions such as an improvement in rapeseed root exploration. The consequences were an increase in the nitrogen use efficiency in intercrops. The intercrop with faba bean and lentil showed the best results in terms of autumn growth, weed control, reduction in rape winter stem weevil damage, and rapeseed N content in spring and yield. Intercropping frost-sensitive legume crops with winter oilseed rape is thus a promising way to reconcile yield and reduction in pesticides and fertilizer use and perhaps to benefit more widely to the cropping system.
Keywords:Intercropping / winter oilseed rape / companion plants / legume crops / agroecological services Résumé -Associer des légumineuses gélives au colza d'hiver contribue à réduire la compétition des adventices, les dégâts d'insectes, et à améliorer l'efficience d'utilisation de l'azote. Associer des plantes au sein d'un agroé-cosystème est mis en avant comme un levier agroécologique permettant de réduire les intrants tout en maintenant la rentabilité. En France, le mélange de légumineuses gélives en association avec le colza d'hiver est une pratique qui présente des intérêts potentiels et commence à se développer chez les agriculteurs. L'objectif de ce travail est d'étudier les intérêts et limites de trois associations en termes de croissance et de rendement du colza, de maîtrise des adventices et de dégâts de charançon du bourgeon terminal. Des expérimentations ont été conduites des 2001 à 2014 dans 4 lieux. Les couverts associés à base de légumineuses gélives permettent d'augmenter la biomasse totale produite et la quantité d'azote aérien en entrée hiver, comparé au colza seul. À l'automne ils contribuent à la réduction de la couverture du sol par les adventices et des dégâts occasionnés par le charançon du bourgeon terminal, notamment pa...
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