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International audience; Evaluating and improving cropping systems is essential to reduce nitrate leaching, improve drinking water quality and prevent eutrophication. Since the intensity of nitrogen (N) leaching varies greatly spatially and is difficult to measure, crop models are useful tools to quantify the influence of climate, soil and agricultural practices on N leaching. Our objective was to develop a simple model with low input data and calibration requirements to predict nitrate leaching from a variety of crop fields over large areas, such as watersheds, for which data are often limited. The AqYield model is a simple model with few inputs that has estimated sufficiently well drainage and water flows for several crops and rotations. Based on this model, we developed AqYield-N, which considers the major N flows in the soil–plant system, including mineralization, plant uptake and leaching at a daily time step. The present study presents the development and formalisms of AqYield-N. We developed AqYield-N based on simple and robust formalisms and low requirements for input data and parameters. As much as possible, we used equations already published and validated in the scientific literature. We then evaluated AqYield-N using observed experimental N leaching data. Its estimates were satisfactory for three contrasting pedoclimatic situations and for various crops and bare soil. Although the model is simple and requires only a few inputs, it was as accurate as more complex crop models widely used and evaluated in the agronomic literature, such as STICS. The study demonstrated the potential of AqYield-N to estimate the influence of management practices on N leaching. AqYield-N, whether alone or integrated in larger-scale modeling approaches, can be used to predict leaching during crop rotations at field and large scale to evaluate the influence of various agroecological practices on N leaching.

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; The implementation of agro-ecological practices such as rotation diversification and cover crop are a well-known solution for limiting pollutions and developing ecosystem services (e.g. soil fertility, biological regulations, climate change regulation). However, covering soils may significantly modify water flow in soils and hydrosystems with possible trade-offs between green and blue water flows. Accordingly, one key issue is to assess to what extent the development of diversified agricultural systems at landscape level can lead to water shortage problems in watersheds. To deal with this issue, we are implementing an integrated assessment and modelling (IAM) approach to assess impact of scenarios of development of agro-ecological practices in the Aveyron basin (800 km²) located in the southwest of France. This catchment is characterized by an intensive agriculture dominated by feedstock cereals and irrigated maize cropping and frequent and intense water shortage issues. The MAELIA multi-agent simulation platform (http://maelia-platform.inra.fr/) is used to perform the IAM approach. MAELIA simulates interactions between the farming practices, hydrology of the different water resources and water management decisions within a catchment area, at high spatial (field) and temporal (day) resolutions. It therefore allows the assessment of environmental, economic and social impacts of the combined changes in agricultural activities, water management strategies and climate. In this study, MAELIA is run on different scenarios in order to assess effects of irrigation optimisation, rotation diversification, cover crop, apply alone or in combination in different locations. The final objective is to identify to what extent there are important trade-offs between agricultural and water resource issues and what would be strategies to limit or overcome these trade-offs. Results of the whole set of simulations will be presented during the conference.

International audience; Cover crops are used during fallow periods to produce ecosystem services, especially those related to N management such as (i) capturing mineral-N from soil to reduce nitrate leaching, and (ii) improving N availability for the next main crop (green manuring). Bispecific mixtures consisting of legume and nonlegume species could simultaneously produce these two services of nitrate saving and green manuring. The magnitude of these services can be estimated from indicators of agroecosystem functions such as crop growth rate, crop N acquisition rate and the C:N ratio of the cover crop. We developed a conceptual model for each indicator which was described using general linear models. A three-step procedure was used: (1) represent the behavior of each species based on a sub-model and calibrate each species in bispecific mixtures; (2) validate the complete mixture models, corresponding to the sum of the two species sub-models, and the proportion of each species in the whole cover, and (3) validate the generality of sub-models and complete-mixture models to predict the agroecosystem function indicators of species in mixture not used for calibration. The combined use of (i) potential agroecosystem functions measured in sole crop in non-limiting conditions, (ii) difference in leaf functional traits, as indicators of plant strategies and (iii) environmental factors, was efficient in fitting and predicting the level of agroecosystem functions provided by a cover crop species in mixture in actual conditions. The models fitted for bispecific mixtures were efficient to represent the behavior of each species in mixture and toestimate the legume proportion which expressed the species dominance. The models were evaluated as satisfactory for crop growth rate and C:N ratio for their generality in predicting the agroecosystem functions provided in mixtures by other species not used in the model calibration step, which illustrates the relevance and robustness of the approach.

International audience; Cover crops are increasingly used in agriculture to provide a variety of ecosystem services (e.g. reducing nitrogen leaching, storing carbon in soils) during fallow periods, but it can be challenging to successfully establish them in summer, when water availability may be low. Thus, it is crucial to better quantify, understand and predict the emergence date of a variety of cover crops from multiple contexts in impact assessment studies. The objectives of this study were to 1) analyze variability in emergence dynamics among cover crops grown in fields, 2) identify variables that influence emergence the most and use them to develop a simple model to predict emergence date and 3) calibrate the STICS model to improve its predictions of cover crop emergence. STICS was chosen because it is a dynamic soil-plant model widely validated in the literature for simulating the production of cover crop services. We analyzed emergence dynamics of ten cover crop species sown under a variety of soil, climate and sowing conditions from 18 experimental sites across France. We developed and independently evaluated a static model based on these data to predict the number of days until emergence. We then calibrated STICS using the same data. Results revealed a mean emergence duration of 12 days for all species, but with high variability among experimental sites and years. The simple static model contained only three variables, with the number of consecutive days without significant water input after sowing the most significant. Overall, both the model and STICS predicted emergence date well in the calibration and validation datasets. Accurate prediction of soil moisture in the seedbed and soil water balance is a key factor to accurately predict cover crop emergence. Accurately predicting emergence of cover crops in crop models will help to assess the former’s ability to provide ecosystem services in cropping systems in current and future climates.

International audience; Designing cropping systems that are well-adapted to water-limited conditions is one challenge of adapting agriculture to climate change. It requires estimating impacts of current and future cropping practices on crop water use and water resource availability in agricultural areas. Crop models such as AqYield are useful tools for evaluating effects of climate, soil and crop practices on evapotranspiration (ET) and drainage that directly impact soil available water (AW). AqYield is a simple model with few input data that has already been satisfactory evaluated for spring crops in southwestern France. Our main objective was to evaluate the ability of AqYield to predict components of soil water balance at the field level for crop rotations. First, we calibrated and evaluated AqYield predictions for winter wheat in France under a wide range of contrasting climatic and soil conditions. Fifty experimental situations (site x year x management) were chosen for calibration. AqYield was evaluated (i) for winter wheat in nine experimental situations, using daily drainage and ET data, and (ii) for two crop rotations on two fields with 7-years of continuous measurements of daily ET flux. During calibration, AqYield predicted soil AW in the contrasting situations with a model efficiency of 0.83, in the same range of accuracy as those of other widely published models. AqYield also predicted ET accurately from calibration and validation datasets, with a model efficiency of 0.84 and 0.69, respectively, for monthly ET. AqYield predicted daily and monthly drainage less accurately, although the range of drainage during the cropping period was predicted well. At the crop-rotation scale, AqYield yielded acceptable predictions of ET for contrasting climate conditions and crops. Whereas AqYield is simple and requires only a few input data, it accurately predicted ET of cropping systems. It therefore could be useful as a module in more complex modeling approaches.

International audience; Cover crops provide ecosystem services such as storing atmospheric carbon in soils after incorporation of their residues. Cover crops also influence soil water balance, which can be an issue in temperate climates with dry summers as for example in southern France and Europe. As a consequence, it is necessary to understand cover crops’ long-term influence on greenhouse gases (GHG) and water balances to assess their potential to mitigate climate change in arable cropping systems. We used the previously calibrated and validated soil-crop model STICS to simulate scenarios of cover crop introduction to assess their influence on rainfed and irrigated cropping systems and crop rotations distributed among five contrasted sites in southern France from 2007-2052. Our results showed that cover crops can improve mean direct GHG balance by 315 kg CO2e ha-1 yr-1 in the long term compared to that of bare soil. This was due mainly to an increase in carbon storage in the soil despite a slight increase in N2O emissions which can be compensate by adapting fertilization. Cover crops also influence the water balance by reducing mean annual drainage by 20 mm yr-1 but increasing mean annual evapotranspiration by 20 mm yr-1 compared to those of bare soil. Using cover crops to improve the GHG balance may help to mitigate climate change by decreasing CO2e emitted in cropping systems which can represent a decrease from 4.5 to 9% of annual GHG emissions of the French agriculture and forestry sector. However, if not well managed, they also could create water management issues in watersheds with shallow groundwater. Relationships between cover crop biomass and its influence on several variables such as drainage, carbon sequestration and GHG emissions could be used to extend our results to other conditions to assess the cover crops influence in a wider range of areas.

International audience; Stakeholders from academic, political, and social spheres encourage the development of more sustainable forms of agriculture. Given its scale and scope, the sustainability transition is a challenge to the entire agricultural sector. The main question is, how to support the transition process? In this article, we explore how agricultural science can address the sustainability transition of farming systems to understand and support transition processes. We discuss the potential for articulating three research approaches: comprehensive analysis, co-design, and simulation modeling. Comprehensive analysis of the sustainability transition provides perspectives on the interplay between resources, resource management, and related performances of farming systems on the one hand and technical, economic, and sociocultural dimensions of change on the other. Co-design of the sustainability transition stimulates local-scale transition experiments in the real world and identification of alternatives for change. Simulation modeling explores future-oriented scenarios of management at multiple levels and assesses their impacts. We illustrate the articulation of research approaches with two examples of research applied to agricultural water management and autonomy in crop-livestock systems. The resulting conceptual framework is the first one developed to organize research to understand and support the sustainability transition of farming systems.

Sunflower (Helianthus annuus L.) crop is often labelled as environmental-friendly for many objective reasons: limited amounts of N fertiliser, no irrigation, and limited use of pesticides. In addition, sunflower has a potential for providing multiple ecosystem services in diverse cropping systems (e.g. pollinators feeding). However agroecological innovations have been less developed or disseminated than for cereals or oilseed rape. Based on results from the sunflower research consortium in Toulouse (Mestries and Debaeke. 2016. Journées d’échanges Tournesol, 28 et 29 juin 2016, Toulouse (France)), we illustrate some innovating and promising approaches for more agroecological practices in sunflower cropping. Our results suggested that: integrated crop management could be proposed to limit the use of pesticides and mitigate crop damages; cover crops could be used as biofumigants to control soilborne diseases in sunflower; intercropping sunflower with soybean could be a valuable option for maximizing resource-use efficiency in low-input environments; sunflower yield could bemaintained at good level in very low input cropping systems. Previous examples point out how agroecological principles could be applied to sunflower crop to improve its production in low-input conditions, and enhance the ecosystem services deliverable by this oilseed crop., La culture de tournesol (Helianthus annuus L.) est souvent qualifiée de respectueuse de l’environnement en raison de sa faible dépendance aux apports d’engrais, à l’eau d’irrigation et aux applications de pesticides en végétation. Par ailleurs, le tournesol contribue à de nombreux services écosystémiques au premier rang desquels l’alimentation des pollinisateurs. Cependant, très peu d’innovations agroécologiques ont été mises en avant sur cette culture contrairement à ce qui a été développé en céréales ou en colza. En nous basant sur les travaux récents du consortium de recherche sur le tournesol basé à Toulouse (Mestries et Debaeke. 2016. Journées d’échanges Tournesol, 28 et 29 juin 2016, Toulouse (France)), nous illustrerons plusieurs approches innovantes et prometteuses pour augmenter la performance agroécologique de la culture de tournesol. Ainsi nos résultats montrent que : des méthodes de protection intégrée peuvent être proposées pour limiter l’application de pesticides et atténuer les pertes de rendement ; des cultures intermédiaires (brassicacées) pourraient être utilisées pour la biofumigation des sols et le contrôle de maladies telluriques en tournesol ; l’association culturale avec le soja pourrait constituer une option intéressante pour maximiser l’utilisation des ressources en bas intrants ; le rendement du tournesol peut être maintenu à un bon niveau dans des systèmes à très bas niveaux d’intrants. Les exemples précédents illustrent comment les principes de l’agroécologie peuvent également être appliqués au tournesol pour améliorer la production dans les situations à bas niveaux d’intrants et plus largement les services écosystémiques apportés par la culture.

International audience; Background and aims During the fallow period, non-legume cover crop species can capture mineral nitrogen (N) and thus decrease nitrate leaching, whereas legume cover crop species can provide a green manur- ing service that increases N availability for the subse- quent crop. The aim of our study was to investigate the ability of bispecific mixtures to simultaneously produce these two services of N management in relation to their interspecific interactions. Methods Three field experiments were conducted at contrasting sites from summer to autumn to evaluate 25 mixtures and 10 sole crops. We measured biomass, N acquisition, C:N ratio and soil mineral N. Ecosystem services were assessed using both experimental data and simulation model predictions. Results Overall, prediction of N mineralized from cover crop residues was significantly higher for mixtures than for non-legume sole crops. Predictions of nitrate leached after mixtures did not differ significantly from those after non-legume sole crops and remained significantly lower than those under bare soil, especially for mixtures with turnip rape which benefitted greatly from being in mixtures. Conclusions Some of the mixtures provided a choice of compromises between the two ecosystem services, which helps define solutions for adapting mixture choice according to the site’s soil and climate character- istics and to fallow period management.

National audience; A wide range of species can be sown as cover crops during fallow periods to provide vari- ous ecosystem services. Plant establishment is a key stage, especially when sowing occurs in summer with high soil temperatures and low water availability. The aim of this study was to determine the response of germination to temperature and water potential for diverse cover crop species. Based on these characteristics, we developed contrasting functional groups that group species with the same germination ability, which may be useful to adapt species choice to climatic sowing conditions. Germination of 36 different species from six botanical families was measured in the laboratory at eight temperatures ranging from 4.5 – 43°C and at four water potentials. Final germination percentages, germination rate, cardinal temperatures, base temperature and base water potential were calculated for each species. Optimal temperatures varied from 21.3 – 37.2°C, maximum temperatures at which the spe- cies could germinate varied from 27.7 – 43.0°C and base water potentials varied from -0.1 to -2.6 MPa. Most cover crops were adapted to summer sowing with a relatively high mean optimal temperature for germination, but some Fabaceae species were more sensitive to high temperatures. Species mainly from Poaceae and Brassicaceae were the most resistant to water deficit and germinated under a low base water potential. Species were classified, independent of family, according to their ability to germinate under a range of temperatures and according to their base water potential in order to group species by func- tional germination groups. These groups may help in choosing the most adapted cover crop species to sow based on climatic conditions in order to favor plant establishment and the services provided by cover crops during fallow periods. Our data can also be useful as ger- mination parameters in crop models to simulate the emergence of cover crops under differ- ent pedoclimatic conditions and crop management practices.

International audience; Cover crops can produce ecosystem services during the fallow period, as reducing nitrate leaching and producing green manure. Crop growth rate (CGR) and crop nitrogen acquisition rate (CNR) can be used as two indicators of the ability of cover crops to produce these services in agrosystems. We used leaf functional traits to characterise the growth strategies of 36 cover crops as an approach to assess their ability to grow and acquire N rapidly. We measured specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen content(LNC) and leaf area (LA) and we evaluated their relevance to characterise CGR and CNR. Cover crop species were positioned along the Leaf Economics Spectrum (LES), the SLALDMC plane, and the CSR triangle of plant strategies. LA was positively correlated with CGR and CNR, while LDMC was negatively correlated with CNR. All cover crops could be classified as resource-acquisitive species from their relative position on the LES and theSLA-LDMC plane. Most cover crops were located along the Competition/Ruderality axis in the CSR triangle. In particular, Brassicaceae species were classified as very competitive, which was consistent with their high CGR and CNR. Leaf functional traits, especially LA and LDMC, allowed to differentiate some cover crops strategies related to their ability to grow and acquire N. LDMC was lower and LNC was higher in cover crop than in wild species, pointing to an efficient acquisitive syndrome in the former, corresponding to the high resource availability found in agrosystems. Combining several leaf traits explained approximately half of the CGR and CNR variances, which might be considered insufficient to precisely characterise and rank cover crop species for agronomic purposes. We hypothesised that may be the consequence of domestication process, which has reduced the range of plant strategies and modified the leaf trait syndrome in cultivated species.

Several studies have already demonstrated the usefulness and efficiency of catch crops to reduce nitrate leaching from cropping systems into groundwater. Catch crops must be sown in summer in a temperate climate, when the soil is often dry after the main crop harvest. This can lead to poor crop establish- ment. The present study uses a model to explore differences in the emergence rates of catch crops in summer for a wide range of soil and weather conditions that occur in France and identifies the main causes of failure. The SIMPLE model predicts the emergence duration and rate of crops by considering species and seed characteristics in interaction with seedbed conditions (temperature, moisture, clods and surface crust). The model was previously validated for white mustard and seems appropriate for the present work of simulating ryegrass and vetch emergence under contrasted weather and water stress conditions. Simulations were performed for a wide range of pedoclimatic conditions and sowing prac- tices (dates, depth and seedbed structures). Soil water content and temperature in the upper layers of the soil were first simulated with the STICS soil-crop model and were then validated in an initial step by comparing simulations with experimental data. These outputs were then used as input data for the SIMPLE emergence model. Results showed that, on average, the emergence rates of catch crops sown in summer were sufficient (>75%), regardless of species and sowing technique. Simulations indicated that a poor emergence rate (

International audience; Cover crops grown in rotation with cash crops provide ecosystem services by reducing pollution and anthropogenic inputs. Among cover crop families, crucifers can efficiently prevent nitrate and sulphate leaching by catching residual soil mineral nitrogen (N) and sulphur (S) (N and S catch crop services). Crucifers also have a unique capacity to suppress pathogens due to the biocidal hydrolysis products of endogenous secondary metabolites called glucosinolates (GSL). However, compared to legume cover crops, crucifers provide less mineralised N to the subsequent main cash crop (N green manure service). Bispecific crucifer–legume cover crop mixtures can be seen as a potential solution to increase biodiversity and to combine ecosystem services of both species. However there is a lack of information on the impact of plant–plant interaction on levels of ecosystem services linked to the N and S cycles and GSL production compared to sole crops. The aim of our study was to assess production of all these ecosystem services for a wide range of bispecific crucifer-legume mixtures in comparison to sole crops.Experiments were conducted at two sites (near Toulouse and Orléans, France) over two years where few cultivars from eight crucifers (rape, white mustard, Indian mustard, Ethiopian mustard, turnip, turnip rape, radish and rocket) and nine legumes (Egyptian clover, crimson clover, common vetch, purple vetch, hairy vetch, pea, soya bean, faba bean, and white lupin) were tested in sole-crop and in 98 bispecific mixtures (substitutive design of 50%-50% sole crops). Crucifer - legume bispecific mixtures provided the same N and S catch crop service (mean soil acquisition of 50 kg N ha-1 and 12 kg S ha-1) and significantly increased the N green manure service (mean mineralisation of 22 kg N ha-1) compared to pure crucifers (mean mineralisation of 8 kg N ha-1). Despite half the density of crucifers, S green manure service was only reduced by 15% in the mixture (mean mineralisation of 5.5 kg S ha-1). Furthermore, crucifers in mixtures have the same GSL types and concentrations as in sole crops while they tend to have more biomass per plant. As a result, despite halving the crucifer density, GSL production on an area basis declined by only 19% in mixtures. On a species basis, despite the high and variable competition for abiotic resources generated by crucifers, no incompatibility of development was observed in mixtures. Overall crucifers and legumes are sufficiently complementary to provide the expected multi-ecosystem services. Our study confirms for a wide range of cover crop species and on 4 sites x years that crucifer-legume mixtures can provide multi-ecosystem services beyond well-known N management services. Therefore it can be recommended to diversify the species included in cover crops in order to provide a high level of multi-ecosystem services and to secure the success of cover cropping.

International audience; Multi-service cover crops are used to provide ecosystem services, particularly for nitrogen management, such as “nitrate catching” and "green manuring" effects. Sowing cover crop mixtures including legumes and non-legumes have the advantage of combining the provision of both services related to N management thanks to phenomena of niche complementarity and/or facilitation in the capture of abiotic resources. When complementarities are optimized, these species mixtures can achieve both effects similarly to those provided by the average of mono specific cover crops, especially for nitrate catching. In addition, the complementarity for the access to light thanks to species having different aerial architectures and contrasted temporal complementarities enable them to obtain services in relay, in particular in the case of the longest fallow periods over mid-Spring. However, in order to achieve the targeted services, attention must be paid to limit competition between species in particular during early stages.

Mini Review This paper aimed at synthetizing: i. Impact of sole grain legume at the rotation level, ii. Potential of grain legume intercrops for improving yield and cereal protein content and iii. Potential of cover crops including intercropped forage legume to achieve simultaneously nitrate capture and green manuring ecosystem services.

International audience; Stakeholders from academic, political or social spheres encourage the development of more sustainable forms of agriculture. Considering the scale and scope of the sustainability transition, it is challenging to the agricultural sector at large. The main question is how to support the transition process? In this communication, we expose how wicked problems related to the sustainability transition of farming systems can be addressed by agricultural science to better understand and support transition processes. We elaborate on the potential for articulation of three research approaches: comprehensive analysis, co-design and simulation modelling that refer to different stances and methodological choices. Comprehensive analysis of the sustainability transition of farming systems provides historical or snapshot perspectives on agricultural and institutional contexts and on the interplay between on one hand, the resources, their management and related performances of farming systems and on the other hand technical, economic and sociocultural dimensions of change. Co-design of the sustainability transition of farming systems stimulates local-scale experiments of transitions in the real world and the identification of alternatives for change from the farming system level to the territorial level. Simulation modelling consists of explorations of scenarios of management at different levels and assessment of their impacts. It offers a future-oriented perspective on transitions. We illustrate this potential for articulation of research approaches by taking the case of two examples of research conducted in our multidisciplinary research group applying to agricultural water management and autonomy in crop-livestock systems. The resulting conceptual framework is the first proposed to organize research to better understand and support sustainability transitions in the agricultural sector.