Abstract EN:

Cereal-legume intercrops are gaining increasing interest in Europe because of low-input preoccupations, preservation of environment and biodiversity. Previous studies had shown that intercropping performances are highly dependant on soil N availability. This practice could provide interesting applications to develop crops for multi-service outcomes along with lower inputs (particularly N). However, very few references are nowadays available to allow N management of intercrops for contrasted production targets. The objectives of this work was (i) to use current knowledge on winter pea-wheat intercrop in order to study whether N fertilization could be a helpful tool to manage such intercrop towards production targets under a conventional agriculture; (ii) to improve knowledge on the response of intercrop to different N-availability dynamics (N resources sharing; inhibition and reversibility of Symbiotic Nitrogen Fixation (SNF)); (iii) to give propositions towards decision rules about Nmanagement of pea-wheat intercrops for different production goals. Our field experiments demonstrated that N-fertilization is an efficient tool to manage pea-wheat intercrop, notably contribution of cereal in total intercrop yield, which is nowadays a badly controlled criterion. N-supply favoured cereal growth to the detriment to the legume. Cereal is more competitive than the legume for mineral N resources if N-application occurs before pea beginning of seed filling. However, the intensity of the response to date of N-fertilizer application is variable according to gap between intercrops species in growth dynamics and stage of development. This is determinant for N-sharing and SNF response. Experiments under greenhouse conditions investigated inhibition effect of nitrate and ability of pea SNF to recover through a structure –function analysis according to different stages of nitrate exposure. Nitrate reduced rate of nodule establishment when nodulated root were exposed to nitrate during vegetative phases while it entailed damage on existing nodules when applied during flowering and seed filling. Nitrate exposure always decreased specific activity of nodules. Moreover, the ability to recover of SNF after nitrate removal is partly dependant on level of C availability to nodules. Thus, pea SNF can recover when a short-term inhibition by nitrate occurs before seed filling stages, which is in agreement with our own field observations.