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International audience; During the fallow period, crucifers grown as catch crops are known to effectively reduce nitrate leaching, while legumes act mainly as green manure by releasing large amounts of mineral nitrogen (N) for the subsequent cash crop once incorporated into the soil. Crucifer-legume cover crop mixtures could be an effective solution for obtaining these two ecosystem services because they combine advantages of both species. However, crucifers might be a poor companion crop due to their high competition for abiotic resources and a potential allelopathic effect on legumes when grown with them. The aim of our study was to assess performances of a wide range of bispecific crucifer-legume mixtures to provide both catch crop and green manure services. A two-year experiment was conducted at two sites (near Toulouse and Orleans, France) where cultivars from eight crucifer species (rape, white mustard, Indian mustard, Ethiopian mustard, turnip, turnip rape, radish and rocket) and nine legume species (Egyptian clover, crimson clover, common vetch, purple vetch, hairy vetch, pea, soya bean, faba bean, and white lupin) were tested in sole-crop and bispecific mixtures (substitutive design of 50%-50% sole crops). We measured cover crop biomass and N acquisition to assess the soil nitrate catch crop service and N green manure service for the subsequent cash crop. In all experiments, compared to bare soil, crucifer-legume mixtures and crucifer sole cover crops provided the same level of nitrate catch crop service by reducing soil mineral N by an average of 59%, while legume sole cover crops reduced it by at least 35%, which is significant. In addition, within 6 months after termination, crucifer-legume mixtures mineralised more N (mean of 22 kg N ha(-1)) and thus had a larger N green manure effect for the subsequent cash crop than crucifer sole cover crops (mean of 8 kg N ha(-1)). This was due to greater N acquisition and a lower C:N ratio of crucifer-legume mixtures; even though crucifers always had advantage in acquiring N, legumes acquired enough N to provide an effective green manure service. These results were consistent in all of our experiments, which represent a wide range of crucifer-legume cover crops, demonstrating their generality. They also demonstrate the compatibility and complementarity of these species when grown together. In conclusion, combining crucifers and legumes as cover crops is an effective solution for obtaining multi-ecosystem services related to N recycling by providing both nitrate catch crop and N green manure services.

International audience; Grasslands provide numerous ecosystem services but their sustainability is threatened by climate change. As plant functional diversity is expected to stabilize ecosystem functions, we tested whether mixing species with contrasting root systems could improve the resilience of Mediterranean grasslands under increasing aridity. We hypothesized that root functional identity (RFI) and diversity (RFD) respectively determines and improves soil water uptake capacity, aboveground biomass (AGB) production and resilience after drought stress (=post-stress AGB/pre-stress AGB). Monocultures, two- and three species mixtures of two groups of perennial grasses (cultivars and native species) were compared in a twin 3-years field experiment under two levels of summer drought in southern France. RFI and RFD were assessed as the mean and variance of multiple root traits (rooting depth, deep root mass fraction, root tissue density, root diameter and specific root length) measured in species monocultures. AGB and resilience were assessed from annual harvests; total transpirable soil water (TTSW) and evapotranspiration in summer (ET_sum) were assessed through the monitoring of soil water content. For both groups of species, RFI was a major predictor of TTSW and resilience, but not of AGB or ET_sum. Greater water uptake, especially from deep soil layers, increased resilience. Rooting depth distribution determined the potential depth of water uptake while root morphology influenced the precision of water uptake along the soil profile. However, RFD only marginally improved AGB production and resilience, although long-term effects of RFD should be tested. Designing artificial plant communities under water-limited conditions should therefore prioritize the maximization of rooting depth and root distribution along the soil profile. Diversifying root morphological traits associated with resource acquisition could also have a positive impact. The similarity of results between cultivars and native species suggests that agro-ecological guidelines for species assembly can be based on advances of functional ecology in natural ecosystems.

International audience; Cropping system models are powerful tools for regional impact assessment, but their input data requirements for large heterogeneous areas are difficult to fulfil. Hence, the objectives of this paper are to present low-data approaches for specifying detailed management data required by cropping system models, and for calibrating default crop parameters applied to 12 regions in the European Union (EU). Various downscaling and upscaling procedures for different data types are applied to address both objectives. The Agricultural Production and Externalities Simulator (APES) model is used for illustrative purposes. Combining easy-to-collect regional crop management information and expert knowledge enables to develop generic, expert-based rules for specifying crop management. Effects of these expert-based management rules on simulated yields and nitrogen leaching are illustrated using APES. Simulated yields of grain maize, soft wheat and durum wheat using default crop parameters for phenology are compared with crop yields observed in 12 EU regions. The accuracy of the simulated yields was variable, but generally poor. A regional calibration factor Kpheno is developed based on the temperature sum of the average sowing and harvest dates of the three crops in each region. Applying this calibration factor improved the simulated yields in all cases. Results suggest that it is possible to develop expert-based management rules and to capture yield variation across the EU by using the presented low-data approaches.