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Two different modes of dairy farming intensification in two adjacent sub-watersheds in the headwaters of the South Fork of Sugar Creek in Ohio, USA, are compared with the potential sustainability consequences in connection to landscape structure and patterns as they impact water quality. A survey was administered between 2005 and 2007 in the southern part of the Sugar Creek watershed where we interviewed 28 Amish and non-Amish farmers. We collected data at the field level on farms totaling 3422 ha to characterize intensifications in production under divergent management strategies and to assess the collective implications for the environmental impacts. In addition, water quality was monitored bi-weekly from 2010–2018 using nutrient concentrations at the sub-watershed outlets and in 1998 and 2017 using instream habitat and biological assessments across both sub-watersheds. The main result was that, despite contrasting farming and cropping systems (small versus large farms, animal grazing versus feed), both Amish and non-Amish dairy operations had increased the number of cows and milk per cow on their farms with similar organic nutrient production by animals per hectare farmed. Equally, surface water quality assessed through our monitoring program was similar with both systems showing decreasing nutrient enrichment and increased habitat quality. Interestingly, these equivalent intensifications and environmental impacts were realized despite contrasting demographics and land use patterns found when comparing Amish and non-Amish operations. Collectively, these results illustrate the need to include socio-cultural dimensions to truly capture the trajectory of development as it pertains to the intersection of sustainability and intensification—especially since the complexity of interactions occurring can potentially mask impacts relative to sustainable water resources management.

article publié en ligne le 10 avril 2019; International audience; AbstractFarmers are being urged to change their practices in order to reduce agricultural pollution. These changes may affect working times and organization, and farmers often mention this to explain the difficulties they have in adopting a new practice. But little is known about the work-related changes (e.g., working time, organization, skills) engendered by a change of farming practice, or about the information that farmers need for deciding on and implementing a new practice. In order to design tools to help farmers when adopting more agroecological practices, the objective of this paper is to identify what work-related information is useful to them for changing their practices. We interviewed 16 farmers in France and we then characterized the types of work-related information they had applied. We focused both on changes that were systemic (reducing tillage or diversifying crops) or less systemic (low-volume spraying or mechanical weeding). We performed a qualitative analysis with an iterative method, alternating between gathering data from the farmers and theorizing about what happens on the work front. We then performed a quantitative analysis of the results, based on chi-squared tests, to identify which factors influence farmers’ work-related information needs. Our findings showed, for the first time, that farmers apply a wide range of information about work changes, concerning performance of new operations, resources used, work organization and competition between activities, and the arduous or rewarding nature of farm work. We showed that the types of information needed change during the process of introducing a new practice. In the first phase, farmers gather mainly generic information about the focal operation and the resources required. In the next phase, they run innovation experiments, producing their own information on how their work is changing and how to reorganize it. Based on these results, we suggest some paths for designing support tools.

Control of crop pests by their natural enemies provides a valuable but poorly quantified ecosystem service. Many studies have addressed the multiple scale drivers of pest control but results from such studies appear variable, if not equivocal. The variability of landscape responses can result from its modulation factors by local practices, among which pesticide use intensity which affects pests and natural enemies and could be a major driver of natural pest control. In this study, we examine the relative contribution of pesticide use and landscape on biological control along a double gradient of pesticide use and landscape simplification. Eighty commercial fields were monitored during three years in four contrasted regions in France. Biocontrol in each field was estimated using three different types of sentinel preys (Ephestia kuehniellaeggs, Acyrthosiphon pisumaphids and Viola arvensis seeds). For each one, the interaction effects of landscape variables with the intensity of pesticide use on predation patterns were analyzed. The predation of weed seeds was negatively influenced by both pesticide use and landscape simplification, without interaction between the two scales. The predation of Ephestia was negatively influenced by landscape simplification only in case of low pesticide use intensity whereas the effect was positive in case of high pesticide use intensity. There was a significant interaction between pesticide use and the length of interfaces between crops and woods on the predation aphids. These landscape variables had a positive effects on the predation of aphids in case of low or medium pesticide use intensity but a negative effect in case of high pesticide use intensity. These results could indicate that in fields with low local pesticide use, landscape complexity enhance biological control whereas in intensive fields, the presence of semi-natural habitat could be unsuitable for natural enemies adapted to intensive situations.

Farming systems are complex and have several dimensions that interact in a dynamic and continuous manner depending on farmers' management strategies. This complexity peaks in Indian semi-arid regions, where small farms encounter a highly competitive environment for markets and resources, especially unreliable access to water from rainfall and irrigation. NAMASTE, a dynamic computer model for water management at the farm level, was developed to reproduce interactions between decisions (investment and technical) and processes (resource management and biophysical) under scenarios of climate-change, socio-economic and water-management policies. The most relevant and novel aspects are i) system-based representation of farming systems, ii) description of dynamic processes via management flexibility and adaptation, iii) representation of farmers' decision-making processes at multiple temporal and spatial scales, iv) management of shared resources. NAMASTE's ability to simulate farmers' adaptive decision-making processes is illustrated by simulating a virtual Indian village composed of two virtual farms with access to groundwater. (c) 2017 Elsevier Ltd. All rights reserved.

International audience; De nombreux travaux ont mis en évidence que les caractéristiques du paysage environnant les parcelles agricoles influencent les abondances d’ennemis naturels et le niveau de régulation biologiquedans les cultures. Les effets du paysage sur l’abondance de bio-agresseurs sont par contre encore peu étudiés. Les effets du paysage sur la régulation biologique sont parfois contradictoires, souventspécifiques aux sites et de ce fait encore peu généralisables. Des travaux récents suggèrent que ces variations de réponse peuvent résulter d’interactions entre gestion parcellaire et contexte paysager,avec des effets conditionnels du paysage selon le type de gestion parcellaire et inversement un effet de la gestion parcellaire qui peut être modulé par le contexte paysager des parcelles (par ex. Lefèbvre et al. 2016 ; Petit et al. 2017). De plus, on peut se demander si les échelles temporelles prises en compte (année ou au mieux rotation culturale) sont pertinentes ou suffisantes pour expliciter les services derégulation observés. La spécificité locale des réponses biologiques pourrait en effet être liée à des différences entre sites en termes de transformations des paysages sur les dernières décennies.Le projet PEERLESS a traité de la question des effets combinés de la gestion parcellaire et du contexte paysager sur l’abondance de bio-agresseurs (et/ou les dégâts causés) et sur le rendement de la culture. En grandes cultures, les relations entre pratiques agricoles parcellaires, métriques paysagères, abondance de bio-agresseurs et rendement de la culture ont été analysées par PLS-PM dans 74parcelles de blé (adventices, pucerons, criocères) et 42 parcelles de colza (adventices, dégâts des siliques). Les principaux enseignements de cette analyse sont que (1) l’abondance de bio-agresseursest globalement mal expliquée par les modèles malgré la prise en compte détaillée des pratiques de gestion parcellaire (R2 de 4 à 20% selon les bio-agresseurs) ; (2) l’abondance de bio-agresseurs a uneffet neutre ou négatif sur le rendement ; (3) le rendement est globalement bien expliqué, (R2 de 40 à 63%), notamment par les pratiques de gestion parcellaire ; (4) le poids du paysage sur l’abondance debio-agresseurs varie selon les bio-agresseurs et selon la pression phytosanitaire parcellaire. En vergers, on montre de la même façon que les effets du paysage sur l’abondance de carpocapse du pommiervarient en fonction de la pression phytosanitaire exercée dans le verger focal. La proportion de vergers dans le paysage diminue l’abondance des carpocapses dans les parcelles faiblement traitées mais n’a aucun effet dans les vergers traités intensivement. Le projet SEBIOPAG-PHYTO a analysé les variations des taux de prédation de 3 types de proies sentinelles (graines adventices, pucerons, oeufs de lépidoptère) dans 100 parcelles sur deux années consécutives en regard de la pression phytosanitaire parcellaire (IFT) et des caractéristiques du paysage environnant. Il en ressort que, pour tous les types de proies, nous avons systématiquement détecté une interaction significative paysage*IFT sur les taux de prédation malgré l’absence d’effet indépendant de la pression phytosanitaire dans la parcelle. La prédation augmente avec la proportion de culture hôte dans le paysage dans les situations locales de forte pression phytosanitaire. Par contre, dans les situations de faible pression phytosanitaire locale, la prédation décroit quand la proportion de culture hôte augmente. De la même façon, la prédation augmente avec la longueur d’interface entre cultures et milieux semi-naturels si la pression phytosanitaire parcellairevest faible mais on observe la relation inverse si la pression phytosanitaire est élevée. La pression phytosanitaire est donc un déterminant majeur de la modulation des effets du paysage sur la régulation biologique ce qui implique que la gestion parcellaire et les caractéristiques du paysage doivent être considérées conjointement pour promouvoir la régulation naturelle des bio-agresseurs.Ce projet a également permis d’aborder la question des effets des transformations des paysages agricoles sur des temps longs (50 ans) sur la régulation biologique des bio-agresseurs, l’hypothèseétant que les niveaux de régulation observés actuellement peuvent être tributaires des trajectoires d’évolution des paysages et des systèmes d’exploitation agricole. Nous avons mobilisé un cadreméthodologique permettant une analyse intégrée des relations entre les changements de paysage et de gestion agricole sur le contrôle biologique. Sur les 5 régions suivies par le réseau nationalSEBIOPAG, nous avons conduit une analyse systémique combinant lecture de paysage et reconstitution fine par enquête de l’histoire de l’agriculture régionale pour appréhender les évolutionsdes mosaïques paysagères et des pratiques d’utilisation des terres et identifier les principaux facteurs technico-économiques de ces transformations. Ces travaux ont permis de mettre en évidence et dedécrire au sein de chaque région une diversité d’unités fonctionnelles de paysages, caractérisées par des patrons spécifiques d’organisation et d’évolution conjointes du milieu et des activités agricoles. Lacoexistence au sein d’un même territoire géographique d’unités fonctionnelles de paysage aux caractéristiques et dynamiques agro-écologiques différenciées pourrait expliquer une partie desvariations de niveau de régulation observées au sein de chaque région. Ces différents travaux nous amènent à discuter plusieurs points. Le premier est relatif à la nécessité de pouvoir décrire des paysages de pratiques culturales (Puech et al., 2015) notamment la pression phytosanitaire à l’échelle d’un paysage (Lavigne et al. 2014), voire des paysages fonctionnels (Vialatte et al., 2017) pour traiter de la question des niveaux de régulation biologique. Ici, l’accès aux données de pratiques ou aux données biologiques à l’échelle de paysages reste un verrou majeur même si le développement de nouvelles méthodes d’acquisition de données pourrait en partie augmenter notre capacité à décrire le paysage de façon plus fonctionnelle. Le second point porte sur les difficultés méthodologiques liées à l’analyse de données aux échelles paysagères.

International audience; Ce séminaire est une restitution des principales avancées obtenues dans le cadre des projets ANR PEERLESS «viabilité d’une gestion écologique renforcée de la santé des plantes dans les paysages agricoles » (2013-2017) et FRB SEBIOPAG-PHYTO «déterminants agricoles parcellaires et paysagers des variations de niveaux de régulation biologique » (2014-2017). Le séminaire a rassemblé 60 scientifiques, pour moitié extérieure aux unités INRA partenaires de ces projets. Il s'est déroulé à Paris les 27-28 novembre 2017.

For two decades, mixed crop-livestock farms have once again been attracting worldwide interest, in particular in the northern hemisphere, where mixed crop-livestock farms have been decreasing. As they are considered to be a good way of limiting environmental problems while being productive and economically viable, mixed crop-livestock systems could be a way to tackle environmental challenges linked to specialised agriculture. The definition of mixed crop-livestock farming nevertheless includes many different types of farming around the world. According to the level of interactions between livestock and crops within farm, mixed crop-livestock farms could be more or less able to meet sustainability challenges. The research works reviewed are mostly focused on biophysical flows between crops and livestock within farms. Farmers' decisions and practices are not taken into account in these works. Mixed crop-livestock studies are based mainly on technical or economic arguments, or on contrasted case studies of the southern hemisphere. Systemic approaches are needed to allow a rethink of the way in which mixed crop-livestock farming could contribute to sustainable development. To limit misunderstanding, the definition of mixed crop-livestock systems should better explained in research studies on the topic, in particular the level of integration between crops and livestock considered. Specific political incentives would be needed to develop and maintain mixed crop-livestock systems, especially in the northern hemisphere.

Prod 2017-344b SPE équipe EA GESTAD INRA; National audience; Le niveau de compréhension des processus écologiques et de leurs interactions avec les activités agricoles est insuffisant pour que les agriculteurs mobilisent ou intègrent la biodiversité et ses services dans leurs décisions de gestion. En effet, la plupart des études portent sur la biodiversité taxonomique et peu sur la régulation biologique. Elles considèrent les activités agricoles à un grain grossier et à l’échelle annuelle, d’où une impossibilité d’identifier des modalités de conduite technique des exploitations agricoles utiles pour renforcer les régulations biologiques. En parallèle, l’intégration de résultats scientifiques sur la régulation dans les démarches de conseil est peu développée alors que la demande pour des connaissances et des méthodes mobilisables dans le conseil agricole est forte. Le projet Sebiopag-Phyto (Appel d’offre FRB-Ecophyto, 2013) a proposé une analyse interdisciplinaire des interactions entre processus agricoles et écologiques affectant la régulation des bio-agresseurs à différentes échelles d’espace et de temps en s’adossant sur le dispositif SEBIOPAG ‘Un réseau pour l’étude des Services Ecosystémiques assurés par la BIOdiversité dans les Paysages Agricoles (http://sebiopag.inra.fr/ SOERE Ecoscope). Il est constitué de 100 parcelles (grandes cultures, vergers) réparties sur 5 sites d’étude englobant une diversité de situations agricoles et paysagères (Vergers de la basse vallée de la Durance, Armorique, Coteaux de Gascogne, Dijon Plaine de Saône, Plaine et Val de Sèvre). Les objectifs scientifiques du projet sont : · d’analyser le poids relatif de la gestion parcellaire (pression phytosanitaire, autres pratiques) et du contexte paysager des parcelles sur les variations de niveaux de régulation biologique. · de développer sur les 5 sites SEBIOPAG notre capacité à analyser le rôle des transformations des paysages et des systèmes d’exploitation au cours des 50 dernières années sur le niveau de régulation biologique · d’évaluer les possibilités d’intégration des résultats dans les démarches de conseil sur l’efficacité de combinaisons de leviers à mobiliser. Les 100 parcelles SEBIOPAG ont fait l’objet, sur 3 années successives, de mesures de la régulation biologique de plusieurs types de proies sentinelles, de recueil par enquête des itinéraires techniques et d’une cartographie annuelle du paysage environnant les parcelles. Ce suivi a été complété par un diagnostic agraire sur les 5 sites de façon à reconstituer l’évolution des paysages et des systèmes d’exploitation sur 50 ans. En parallèle, nous avons mené une analyse de la littérature scientifique internationale sur les connaissances produites par les études portant sur la régulation biologique, et en particulier sur la façon dont elles sont mobilisées/mobilisables pour le conseil et l’accompagnement. Les principales productions du projet SEBIOPAG-Phyto sont : - Une analyse critique et une validation de la méthode des proies sentinelles pour analyser les variations de niveaux de régulation biologique (Session 1, présentation de Ricci et al) - La mise évidence d’effets interactifs conditionnels entre gestion phytosanitaire parcellaire et contexte paysager sur la régulation qui suggère que la pression phytosanitaire va moduler le fonctionnement écologique de la parcelle et sa dépendance aux autres éléments du paysage (session 2, présentation de Valantin et al; session 3, présentation de Petit et al) - La coexistence, au sein d’un même territoire géographique, d’unités fonctionnelles de paysage aux caractéristiques et dynamiques agro-écologiques différenciées qui pourrait expliquer une partie des variations de niveau de régulation observées au sein de chaque région (session 3, présentation de Petit et al) - Une mise au point bibliographique sur la façon dont les connaissances sur la régulation biologique sont ou peuvent être mobilisées pour l’action (session 5, Thenail et al.)

sous presse; Green-way policies in agricultural landscapes focus on ecological continuity between semi-natural elements (hedgerows, permanent grasslands, woods) and landscape heterogeneity. These policies suggest annual crops and temporary grasslands exhibit a negative or neutral impact on biodiversity. However, recent studies indicated the spatial continuities between different crops (spring vs. winter) showed positive impacts on biodiversity. These landscape patterns were directly related to farmers' decisions regarding the crops cultivated and where the crops were distributed spatially on the farm. The aim of the present study was to evaluate the impacts of di ff erent livestock farming system management types on crop patterns and associated biodiversity (carabid beetles) in agricultural landscapes. We combined empirical analyses of farmers' decision making and ecological data to develop a modeling framework simulating crop allocation and abundance of two different carabid beetle species groups (maize and woody species). Modeling included fi eld, farm, and landscape levels. We simulated different scenarios, where two livestock farming systems, swine and dairy, were combined in different proportions (i.e. number of swine vs. dairy farms) in two agricultural landscapes with varied hedgerow densities. Simulations showed maize carabid species abundance was higher in swine production landscapes due to more frequent spatial continuities between spring and winter crops. In contrast, woody carabid species were more abundant in mixed landscapes (dairy and swine) under high crop diversity. For a given combination of livestock farming systems, simulated landscapes were highly variable in crop acreages and spatial continuities between crops. Our results emphasized the need to manage landscape at a collective level, where crop allocation decisions create more interfaces without modifying livestock farming system combinations.

International audience; Planting and destruction are the two main phases in cover crop management techniques. Their dates and implementation conditions play a key role in terms of the various functions targeted for these crops (nitrate-trapping, erosion prevention, weed control, effect on next crop, etc.). The analysis of the literature therefore focused on cover crop planting and destruction techniques. The aim was to identify the different methods and, if possible, their effectiveness with respect to the success of sowing and destruction. The issue of the implementation of these techniques by farmers was then examined by analysing the constraints in terms of organization of labour and implementation costs.

Les principaux resultats obtenus dans le cadre du projet climaster visent a contribuer au debat sur le changement climatique dans le Grand Ouest de la France. Des analyses de differentes longues chroniques ont porte sur l’evolution climatique en cours. Les analyses sur les temperatures montrent qu’un degre a ete « gagne » en moyenne sur les cinquante dernieres annees. Sur les precipitations, on note des tendances saisonnieres opposees, avec une augmentation l’hiver et une diminution l’ete, surtout au nord du Grand Ouest. Vis-a-vis de l’agriculture, des travaux originaux sur les jours agronomiquement disponibles ont ete realises. Les tendances actuelles et passees des systemes de culture ont ete aussi abordees a partir des chroniques spatiales d’occupation du sol sur des donnees de teledetection innovantes, sur une decennie. La capacite des acteurs agricoles a prendre en compte l’impact du changement climatique a ete caracterisee a partir d’enquetes, de seminaires d’echanges et de reflexions prospectives au sein de groupes d’agriculteurs. En contrepoint, des enquetes avec les acteurs de l’eau ont ete egalement realisees. En conclusion, l’ensemble des travaux de climaster, les methodes choisies, le corpus de connaissances elabore sont la pour « donner a penser » le changement climatique dans le Grand Ouest.

International audience; AbstractDeveloping sustainable crop systems is a major challenge. Presently, management practices are simulated using either biophysical models or simple farmer decision models. As a result, there is a lack of generic models integrating both biophysical parameters and farmer decision parameters. Here, we developed an original graphical plug-in to sketch and implement decision-making models and to link them with biophysical models. For that, we used the RECORD platform, standing for REnovation and COORDination of agro-ecosystem modeling. Different pop-up windows allow to create the model using a decision formalism then to implement the model under the RECORD platform. The sequence of technical operations is formally modeled as a direct multi-graph without retroaction. The plug-in allows defining activities, relation between activities, and decision rules to trigger the different activities. The resulting model is independent of any biophysical model and can then be linked with different crop models. An example is given on an innovative cropping systems part of the MicMac-Design project. The decision-making model is then linked with the STICS crop model.

International audience; Farming activities are major drivers of the landscape-related ecological patterning because of their multiple influences on both non-arable and arable landscape elements and mosaics. Uncertainties still remain about the way individual farmer decisions and the aggregation of their activities in space contribute to these mosaics at local landscape scales, therefore about possible levers of action in farms for ensuring sustainable landscapes. The general objective of the present study was to give an assessment of the way farms contribute to crop-mosaic patterning at local landscape scales. We developed a method for comparing five contrasted local study cases of agriculture (five farm sets), by combining a statistical modeling of crop-rotation organization in farms, from empirical data, and a crop-mosaic simulation approach, applied in each case. Statistical rules of crop rotation allocation to fields in farms were defined from tests involving the following potential allocation factors: (1) farm household-enterprise, (2) field physical environment and (3) farm territory configuration. The statistical rules setup from each set of factors were implemented in rule-based simulations separately for each of the five local study cases. We used a raster representation of fields (one pixel by field), to concentrate on crop-rotation management-related effects, independently from the shape of fields and of diverse perennial landscape elements. An index of connectedness was measured for each mosaic, and was used as an indicator of crop-clustering effects due to crop-rotation organization in farms. The results showed that crop-clustering effects at local landscape scales differed according to the following factors of crop-mosaic patterning: (a) the spatial distribution of crop-rotation allocation factors over the field mosaic, (b) the specialization of crop rotations to their allocation factors, and (c) the development of crop rotations over time. These results also demonstrated that crop rotations, even if run as regular crop sequences over time, lead to significant year to year crop-mosaic variability. The results finally made explicit the differences between local study cases. We conclude from these results by pinpointing trade-offs to find between farm and landscape management.

Runoff and erosion cause frequent damage through muddy floods in the loess belt of Northern Europe. One possibility for reducing damage is to lower runoff on agricultural land by spatially alternating different crops at the catchment level. But crop location results from decisions taken at the farm level. This study aimed to assess the existing leeway to modify crop location in the farms of a catchment, in order to reduce runoff at the catchment's outlet. The case study was the Bourville catchment (1086 ha), cultivated by 28 farmers and located in Pays de Caux, France. First, crop location rules in the 14 main farms of the catchment were analysed on the basis of surveys carried out with farmers, distinguishing spatial constraints from temporal ones. These rules made it possible to simulate crop location on each farm territory for the 2001-2002 crop year. Each field of the catchment was classified depending on whether one or several crops could be sown, taking into account both field history and farmer decision rules. Then two extreme scenarios of crop location in the Bourville catchment were built. Runoff simulation at the outlet with the STREAM model showed that runoff could be reduced while sticking to current farmer decision rules in terms of crop location. Depending on rainfall event characteristics, runoff reduction varied between 13·5 per cent and 4·5 per cent.

In the loam belt of Northern Europe and in the North-western Paris Basin, runoff and erosion may be reduced by changing agricultural practices in the agricultural catchment where runoff is produced. However, such changes may be limited by work planning constraints at the farm level. This study therefore aimed to assess farmers’ leeway to introduce stubble ploughing and mustard (Brassica alba) sowing during the intercrop period. The case study was the Bourville catchment (1086 ha), cultivated by 28 farmers and located in Pays de Caux, France. Firstly, workload was analysed and sequences of cultivation operations were simulated for an average climate for the 14 main farms located in the catchment. This analysis was based on surveys carried out with farmers. It was then possible to determine the number of working days available to perform stubble ploughing and mustard sowing, both of them being efficient practices to reduce runoff at the field level. Results showed that farmers did not have the same leeway as some of them were even unable to perform stubble ploughing or mustard sowing. Then at the catchment level, the impact of changes in agricultural practices on runoff volume at the catchment's outlet was simulated by using the STREAM model. These simulations showed that not taking into account work planning constraints within farms led to overestimating both the possibilities of implementing changes in farms and the efficiency of such changes on runoff reduction.

This paper explores, from an agronomic viewpoint, the way soil surface characteristics may be managed for soil and water conservation purposes in a silty loam soil context (Pays de Caux, France). We first consider the tools used to characterize the impact of farming practices on soil surface characteristics and, as a result, on runoff and erosion processes. The way farming practices modify soil surface characteristics must be considered at various spatial scales, from the metric pattern produced by farm machinery, to the network of field boundaries, headlands and dead furrows at the small-watershed scale. Various time scales (yearly, daily) must also be taken into account. We then describe how a range of agricultural techniques that may reduce runoff risk on farmland can be found. In particular, we show how to analyse the farmers' leeway for adopting more opportune cultivation techniques specifying the impact of these techniques on plant growth or on work organization. But other factors such as social factors (farmers' network) also interfere and should be taken into account in soil and water protection programmes. Copyright © 2004 John Wiley & Sons, Ltd.

In Pays de Caux, runoff and erosion frequently generate damages. Ploughing up grassland is one of the causes of their increase. To apprehend this issue, the authors studied the conceptions of a group of farmers, farming the same catchment, through a socio-anthropological approach. According to this analysis, two types of farms are identified: the ‘managers’ looking at the profitability per hectare, and the ‘livestock farmers’, for whom the global income of farming is more important. The latter are severely depreciated, by the others and by themselves, and are generally not taken over. Nevertheless, their grasslands are more steady than the ‘managers’ ones, and their preservation is important to combat erosion. The Common Agricultural Policy (CAP) does not suggest any measures supporting grassland of these ‘small livestock farmers’. Local subsidies could not only support them economically but could also contribute to decrease their depreciation. This may be a way to manage the risk of soil erosion. However, the results are established at the catchment level and further enquiries are needed to extend them. It is possible to build a network of places in Europe, with the aim of thinking propositions at the CAP level.

Atteindre l’objectif affiché de réduction du niveau d’usage de produits phytosanitaires tout en maintenant les niveaux de production des cultures implique la mise en place de stratégies de protection des cultures alternatives à la lutte chimique. L’adoption de pratiques plus favorables à la biodiversité dans les agroécosystèmes pourrait contribuer à augmenter les services de régulation biologique des ravageurs de culture. Il est établi que la biodiversité des milieux cultivés est modulée par des facteurs naturels et anthropiques agissant à différentes échelles spatiales, allant de la parcelle agricole au paysage, mais la compréhension des mécanismes écologiques qui produisent ces effets reste limitée. Pour produire des connaissances sur les déterminants des niveaux de régulations biologiques, il est nécessaire d’avoir recours à une approche à long terme qui mobilise à la fois une description des systèmes de cultures et une caractérisation écologique du contexte paysager. Pour répondre à cet enjeu a été constitué SEBIOPAG (http://sebiopag.inra.fr), un réseau pour l’étude des Services Ecosystémiques assurés par la BIOdiversité dans les Paysages Agricoles qui appartient au réseau national des observatoires de recherche sur la biodiversité (ECOSCOPE). Les objectifs sont de suivre sur le long terme, et dans des zones paysagères contrastées (i) les services écosystémiques rendus par la biodiversité, (ii) les facteurs qui les influencent (composition et structure du paysages, pratiques agricoles) et (iii) leur évolution dans le contexte des changements globaux (utilisation des terres, climatiques,…).Le réseau SEBIOPAG est constitué de cinq sites : Avignon, Dijon, Chizé, Rennes et Toulouse. En 2013, danschaque site, le paysage a été décrit et cartographié à l’aide de trois descripteurs : la proportion de cultures,l’hétérogénéité et la longueur des interfaces entre cultures et éléments semi-naturels. Puis, dans chaque site, 20 parcelles d’exploitants ont été choisies le long des trois gradients paysagers et d’un gradient d’intensité de pratiques. Les premières mesures (exposition de cartes de prédation) ont été effectuées en 2014 et portent sur une évaluation du potentiel de régulation biologique de trois espèces cibles : Acyrthosiphon pisum (pucerons), Ephestia kuehniella (lépidoptère) et Viola arvensis (adventice).

National audience; L’objet de ce colloque est de partager des connaissances, expériences et outils autour de la modélisation des paysages agricoles, de leur structure et de leur dynamique en considérant la modélisation de la structure physique du paysage agricole et celle des processus socio-techniques qui gouvernent les usages des éléments le constituant (parcelles, fossés, etc.). Par ailleurs, les paysages agricoles sont le support de processus biotiques et abiotiques spatialisés. Les processus biotiques incluent par exemple les dynamiques d’organismes d’importance en agriculture – ravageurs et auxiliaires – ou contribuant à la biodiversité patrimoniale ou ordinaire. Les processus abiotiques incluent par exemple les flux d’eau, d’air, d’éléments minéraux ou organiques. La représentation des paysages en tant que supports (dynamiques) de ces processus et l'analyse de sensibilité des modèles de processus aux variables spatiales font également l’objet de ce colloque. Ce colloque est organisé par le réseau interdisciplinaire PAYOTE qui regroupe des chercheurs et des ingénieurs travaillant sur la modélisation de paysages agricoles pour la simulation et l'analyse de processus écologiques et environnementaux.

Mixed crop-livestock farming is regaining interest worldwide as a way to reduce environmental problemswhile allowing productive and economically viable agriculture. However, the number of mixed crop-livestock farms has been falling steadily in Europe, where production has become concentrated on specialised and enlarged farms. This study aimed to design and assess technical innovations which could enhance the sustainability of mixed farming in the difficult conditions of Less Favoured Areas. It was conducted in a hilly region in south-western France where mixed crop-livestock farming continues to be practiced. Innovative technical scenarios consistent with the two main adaptive strategies implemented by local mixed farms were selected with farmers and other stakeholders. The first, the ‘‘maximising farm autonomy’’ strategy, consisted of sowing forage legumes between two cash crops to achieve herd feed self-sufficiency while maintaining soil fertility. The second, the ‘‘diversifying production’’ management strategy, consisted of adding a heifer fattening unit to increase farm income. Both scenarios were assessed on two actual farms using a whole farm simulation tool, CLIFS, based on feed and manure balances. They then were combined with prospective scenarios on public policies and markets to analyse farmers’ capacity to cope with changes in their economic environment. Under currentconditions, the two technical innovations allowed an increase of the total gross margin per hectare of cultivatedarea by respectively 8.9% and 17.1%. However, under contrasting future political and economic conditions, they were unable to mitigate the impact of drastic shocks. Public policy support would likely be needed to maintain local mixed crop-livestock farms in these contexts. The combination of discussions and simulations using concrete farm cases ensured a lively dialogue between researchers, farmers, and professionals. The process combined a broad range of empirical, technical and scientific knowledge and enriched both individual and collective learning.

Aims: The study aims at applying to a perennial crop the concept of “workable days” developed for annual crops by G. Kreher in 1955. A workable day is a day that provides conditions agronomically correct for work.Methods and results: A survey among grapevine growers was carried out to collect their perception of practice sensitivity to weather variability. The study provided information on working periods, techniques and machinery involved, weather constraints and thresholds generally used by the vine growers, for 21 annual cropping practices. Pesticide spraying against powdery and downy mildew appeared to be the most sensitive to weather parameters. Therefore, this practice was selected for the purpose of modelling workable days, according to decision rules based on the postulate that all weather parameters should be within the acceptable ranges. The model was run over a period of 13 years (1998-2010). Analyses of the outputs pointed out a great variability in the number of workable days from one year to another as well as in the respective proportion of unfavourable weather factors involved in the reduction of workable days. A validation based on the analysis of the actual spraying practices realized over a period of 12 years (1999-2010) showed that 32 % of the treatments were done on a day characterized as not workable by the model. The errors could be attributed to periods of holidays and risky sanitary situations when decision rules had to be bypassed.Conclusion: The model proved to represent rather well the decision rules use by vine growers to carry out their annual cropping practices in relation with the weather variability, within the area of study. The controversial role of the ‘leaf wetness duration’ weather parameter needs to be clarified; it may help to better parametrize the model. In order to improve its performance, the model should be coupled to a disease propagation model.Significance and impact of the study: In a climate change perspective, modelling of workable days can be run with simulated climatic data. It may prove to be useful to adapt vineyard management strategies in terms of innovative cropping practices and equipment.

International audience; As an alternative to conventional farming, organic farming is considered a promising type of production to meet the challenges of modern agriculture. In particular, organic farming is assumed to favour the biological control of pests by their natural enemies and, therefore, is considered a possible way to reduce the use of pesticides. Effects of organic vs. conventional farming on insects natural enemies have been compared, but the results remain uncertain, probably because the diversity of crop management strategies is rarely considered. In this study, we assessed whether or not the diversity of farming practices implemented in organic and conventional farming affects natural enemies of aphids (ladybirds, carabid beetles and parasitoids) in winter wheat. Entomological surveys were carried out in 20 pairs of organic and conventional fields. We interviewed the farmers to identify variables that describe farming practices and identified the most important practices using a ranking approach based on random forests. Abundances of aphids' natural enemies were tested in relation to different levels of description of farming practices (from organic vs. conventional farming to individual practices). We found a large diversity of farming practices, which were evenly distributed along a gradient from organic to conventional farming. Abundances of aphids' natural enemies were greater in organic fields, but the three species groups had different responses to the diversity of farming practices. Ladybirds were influenced by tillage frequency, number of wheat varieties and pesticides, and carabid beetles by tillage frequency, whereas parasitoids were not affected by any practice. Even though the organic vs. conventional farming dichotomy was meaningful to explain aphids' natural enemies abundances, the consideration of more detailed practices improved our understanding of their response to crop management strategies. Our results help identify the level at which agro-ecosystem actors must intervene to promote effective biological control

La polyculture-élevage est de plus en plus reconnue au plan international comme un moyen de limiter les problèmes environnementaux tout en permettant une agriculture productive et économiquement viable

International audience; Landscape ecology has emphasized the key role of spatial heterogeneity as a driver of ecological processes, which has led to a shift from a patch-matrix to a landscape mosaic representation of landscapes. However, in agricultural landscapes, the role of heterogeneity for biodiversity is often studied by considering (semi-) natural elements regardless of the functional heterogeneity of the cultivated mosaic. This mosaic, which emerges from the organization of cropping systems by farmers, is not just heterogeneous in space but also strongly dynamic (i.e. temporally heterogeneous) due to crop phenology, management and sequence. In this paper, based on agronomic and ecological literature we highlight the heterogeneous properties of the cropping system mosaics in space and time, and the implications of this "hidden" heterogeneity for controlling of arthropod population dynamics and persistence. An illustration is then given to propose different methodological approaches to map the hidden heterogeneity of agricultural landscapes. This conceptual and methodological framework concerns various species in agro-ecosystems, including crop and multi-habitat species, as well as species that only disperse through the crop mosaic. This paper suggests that the design of the cropping system mosaics could be complementary to the design of natural areas to manage populations, notably for species of economic interest (pests, natural enemies or pollinators). More empirical work on this topic is crucial, which will require new methodological approaches.

International audience; Application tools for the crop allocation problem (CAP) are required for agricultural advisors to design more efficient farming systems. Despite the extensive treatment of this issue by agronomists in the past, few methods tackle the crop allocation problem considering both the spatial and the temporal aspects of the CAP. In this paper, we precisely propose an original formulation addressing the crop allocation planning problem while taking farmers' management choices into account. These choices are naturally represented by hard and soft constraints in the Weighted CSP formalism. We illustrate our proposition by solving a medium-size virtual farm using either a WCSP solver (toulbar2) or an ILP solver (NumberJack/SCIP). This preliminary work foreshadows the development of a decision-aid tool for supporting farmers in their crop allocation strategies.

International audience

Intensification and specialisation of agriculture in developed countries enabled productivity to be improved but had detrimental impacts on the environment and threatened the economic viability of a huge number of farms. The combination of livestock and crops, which was very common in the past, is assumed to be a viable alternative to specialised livestock or cropping systems. Mixed crop-livestock systems can improve nutrient cycling while reducing chemical inputs and generate economies of scope at farm level. Most assumptions underlying these views are based on theoretical and experimental evidence. Very few assessments of their environmental and economic advantages have nevertheless been undertaken in real-world farming conditions. In this paper, we present a comparative assessment of the environmental and economic performances of mixed crop-livestock farms v. specialised farms among the farm population of the French 'Coteaux de Gascogne'. In this hilly region, half of the farms currently use a mixed crop-livestock system including beef cattle and cash crops, the remaining farms being specialised in either crops or cattle. Data were collected through an exhaustive survey of farms located in our study area. The economic performances of farming systems were assessed on 48 farms on the basis of (i) overall gross margin, (ii) production costs and (iii) analysis of the sensitivity of gross margins to fluctuations in the price of inputs and outputs. The environmental dimension was analysed through (i) characterisation of farmers' crop management practices, (ii) analysis of farm land use diversity and (iii) nitrogen farm-gate balance. Local mixed crop-livestock farms did not have significantly higher overall gross margins than specialised farms but were less sensitive than dairy and crop farms to fluctuations in the price of inputs and outputs considered. Mixed crop-livestock farms had lower costs than crop farms, while beef farms had the lowest costs as they are grass-based systems. Concerning crop management practices, our results revealed an intensification gradient from low to high input farming systems. Beyond some general trends, a wide range of management practices and levels of intensification were observed among farms with a similar production system. Mixed crop-livestock farms were very heterogeneous with respect to the use of inputs. Nevertheless, our study revealed a lower potential for nitrogen pollution in mixed crop-livestock and beef production systems than in dairy and crop farming systems. Even if a wide variability exists within system, mixed crop-livestock systems appear to be a way for an environmental and economical sustainable agriculture.

International audience; Reducing pesticide use in agriculture is necessary to preserve natural resources. However, pest control without pesticides is a challenging issue. In particular, weed infestation may cause severe losses of crop yield. Weeds have been traditionally managed solely at the field level. However, larger scales must be considered because invasive and herbicide-tolerant weeds are spreading over larger scales. This review discusses three spatial scales at which agricultural management might affect the dispersal of weeds and, in turn, their distribution and abundance in agricultural fields. The main points are: (1) at the field level, crop and margin management impact mass effect, i.e., local exchanges between the field margin and the cultivated field; (2) at the farm level crop allocation, the management of field boundaries and agricultural circulation in the farm strongly impact the intensity and direction of weed dispersal; and (3) at the landscape level, the spatial farms distribution controls the distribution of weed habitat and, in turn, landscape species pool and long-distance weed dispersal. We conclude that weed dispersal is driven by agricultural management at multiple scales. Weed scientists should thus extend their view on weed dispersal from within-field scales to among-field and landscape scales.

This article proposes the use of a new model, DIAR (Diagnostic Agronomique du Ruissellement, or Agronomic Assessment of Runoff), for the prediction of the timing of the risk of runoff. DIAR is dedicated to loamy soils which are very sensitive to surface crusting, leading to runoff, soil erosion and muddy flows. The approach is proposed for the north-western European loess belt regions where muddy flows severely impact human activities. The likelihood of runoff is assessed from the sequence of soil surface states generated by cultivation practices. DIAR is based on the calculation of curve number values, for each stage of the soil-surface-state sequence, for calculating runoff for each of these stages. In this study, DIAR is applied to a catchment of 912 ha, cultivated by 26 farmers in the Pays de Caux (Normandy, France) where infrastructures located at the outlet have been damaged several times by muddy flows. Local public authorities involved in reducing muddy flows are eager to limit the agricultural upstream runoff by extending the planting of mustard as a winter cover crop. We tested the efficiency of such a policy on the reduction of the mean runoff. We also tested the year-to-year variability of this efficiency using the acreages of four successive years (1999-2000 to 2002-2003). Finally, the cost-efficiency of the policy was also considered. Though we used the same weather scenario, the initial situation (without much mustard cover) showed a wide year-to-year variation in the total runoff. This variation can be associated with the structure of the farms that cultivate the catchment (Utilised Agricultural Area (UAA) of each farm and percentage of this UAA inside the catchment). Our results showed that the widespread planting of winter cover crops could reduce the runoff by 10-20% compared with the initial situation (depending on the year), and also reduce the year-to-year variability of runoff. For each of the 4 tested years, the cost of the infiltrated m(3), due to each ha of mustard cover, decreases with the increase in mustard cover. It indicates that the present siting of the mustard cover is not as efficient as it could be. We should ask why farmers do not sow it elsewhere.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]DTAM; This paper analyses the potential effect of local agro-environmental policies in promoting multifunctionality in a rural landscape, with a two-scale modelling framework: a regional scale for food demand and a local scale for the forces driving land use. The framework has been designed in four steps. First, the relative influence of the driving factors on the current land use pattern has been analysed. Two scenarios are designed that vary the external demand for the total land use, and alter more or less quickly the specific location factors that drive the landscape pattern. The first scenario considers trends in the external and internal driving forces. The second relies both on totally decoupled farm subsidies and unregulated housing growth. In both scenarios a local agro-environmental policy is introduced and we compare its consequences with the previous scenario's landscape pattern. The third step consists of a modelling exercise that analyses the likely outcome of each scenario on the development of land use patterns on a local scale. Last, these landscape patterns have been translated into ecological indexes that assess the effect of the policy options on the multifunctionality of the local landscape.

Agricultural changes such as intensification and specialization are thought to be the major source of the severe decline of farmland bird populations observed on large spatial scales and over long time spans in Europe. We studied farmers' practices at a local level on 22 farms from the Beauce area, France, with regard to habitat preferences of grey partridge, Perdix perdix L. We focused on the study of vegetation cover because it influences grey partridge's reproduction and survival. The results revealed a high diversity of vegetation cover over the municipal territory. This high diversity can be explained by (1) the difference in the crops cultivated by the farmers, only wheat being cultivated by all the farmers; (2) the diversity of elementary crop sequences implemented, as many as 51 having been identified; and (3) the field size, which varies from 0.5 ha to 57 ha, with 54% of fields smaller than 10 ha. Altogether, this potentially creates six different habitat types, 32% of the arable land surveyed being a likely suitable habitat for the grey partridge. We found that irrigation was the main driving factor of vegetation cover diversity. Indeed irrigation controls the farms' crop acreage, the crop sequences and their spatial pattern and field size. Nonetheless, irrigation practices show both positive, e.g. crop diversity, and negative aspects, e.g. large fields and clutch failure, for ground-nesting birds such as the grey partridge. Based on these results, a GIS modeling of the municipal landscape related to grey partridge's habitat requirements is possible and would allow a deeper analysis of the impact of crop diversity on grey partridge populations. cash crop ecosystems / crop sequences / farmland bird biodiversity / grey partridge / technical farm management

Runoff disregards territorial boundaries, affects farmers as well as other users of space, and necessitates collective action if it is to be combatted. In this article, based on the case of Upper-Normandy, we show that geographical proximity can play a determining role in the struggle against erosive runoff, and we present a new tool for analysing relations of proximity between farmers. First, we use three examples to show that farmers have only limited knowledge of the problem of erosion and are largely incapable of carrying out concerted collective action. That is why Syndicats de basins versants were set up to provide organised proximity. Then we present a new tool for analysing relations of geographical proximity between farmed land and farmsteads, in order to assess the possibilities of coordination between farmers within catchment areas. Our results, based on the characterisation of 1409 communes, clearly show that long distances, the size of farmed agricultural land and the high number of external farmers constitute major obstacles to the creation of ad hoc cooperative processes.

International audience; The biological control of crop pests is a valuable service provided by various beneficial organisms that are naturally present in agricultural landscapes. Semi-natural habitats has long been recognized as essential to preserve beneficial insects, but proof of their efficiency to enhance biological control of pests remains non conclusive. Here, we examined the variability of landscape effect on biological pest control and the way local agronomic practices may modulate it. Biological pest control was monitored in 80 commercial fields (arable crops and orchards) during three consecutive years in four contrasting French agricultural landscapes distributed along a double gradient of pesticide use and landscape complexity measured in a 1 km2 area centred on each field. Biocontrol efficacy in each field was assessed using three types of sentinel preys (weed seeds, moth eggs, and aphids). The effects of landscape simplification, pesticide use intensity and their interaction on the predation of each sentinel prey were analysed using generalised linear mixed models. At local level, the intensity of pesticide use reduced the predation of weed seeds and aphids. At landscape level, the proportion of the monitored crop reduced the predation of weed seeds and moth eggs. Finally, significant interactions between local and landscape factors were detected for each sentinel prey: (i) the predation of moth eggs was negatively influenced by landscape simplification at low pesticide use intensity only, whereas the effect was positive at high pesticide use intensity; (ii) aphid predation significantly decreased with increasing crop-wood interface length and proportion of meadow, but only at high pesticide use intensity; (iii) weed seed predation significantly decreased when land use diversity around the fields increased under high pesticide use intensity and, inversely, increased with land cover diversity around the fields at of low pesticide use intensity. These results suggest that reduction in pesticide use should be associated with the reinforcement of semi-natural habitats in agricultural landscape to enhance natural biocontrol.

Afin de réduire les pollutions agricoles, les agriculteurs sont invités à faire évoluer leurs pratiques. Mais ces évolutions peuvent générer des changements d'organisation et de temps de travail, qu'ils invoquent pour expliquer leur difficulté à changer. Pourtant, les recherches agronomiques sur la prise en considération du travail dans l'accompagnement des dynamiques de changement restent peu nombreuses. Elles ont essentiellement porté sur la gestion des pointes de travail, via l'étude des variations de l'organisation du travail, en considérant des contraintes pédoclimatiques. Cependant, les besoins des agriculteurs en informations sur le travail pour mener à bien un processus de changement vers de pratiques plus agroécologiques restent peu connus. C'est pourquoi cette thèse a pour objectif d'étudier les changements du travail générés par l'introduction de nouvelles pratiques culturales plus respectueuses de l'environnement, et de préciser la nature des informations sur le travail dont ont besoin les agriculteurs, pour identifier des outils d'accompagnement à concevoir. L'enjeu est de faciliter les transitions agroécologiques des agriculteurs. Pour atteindre cet objectif, nous avons déployé une démarche en deux étapes, associant un diagnostic des situations d'usage et des ateliers de conception. Le diagnostic a porté sur les manières dont les conseillers agricoles et les agriculteurs prennent en compte le travail dans le changement. Le premier volet du diagnostic a visé à identifier ce qu'apporte aux agriculteurs l'usage d'outils de simulations du travail existants, afin de déterminer quelles étaient leurs potentialités pour accompagner des agriculteurs dans le changement de pratiques. Nous avons étudié les usages de 7 outils pour identifier les réponses qu'ils fournissent et avons observé 7 réunions d'accompagnement de 58 agriculteurs pour relever leurs questionnements sur les changements du travail. Nous avons montré que l'utilisation de ces outils en prestation individuelle est inadaptée, car trop longue et coûteuse, et que les informations fournies ne répondent que très partiellement aux besoins des agriculteurs. Sur la base de ce constat, le second volet du diagnostic a visé à mieux connaitre ces besoins. Nous avons enquêté 16 agriculteurs sur leur trajectoire de changement de pratiques. L'analyse qualitative et quantitative de ces enquêtes montre que les agriculteurs utilisent une diversité d’informations sur les changements du travail, dont la nature évolue selon l’étape du processus d’adoption de la nouvelle technique. Avant d'essayer, ils recueillent des informations majoritairement génériques, concernant la réalisation des nouvelles interventions et les ressources à mobiliser. Puis ils conduisent des essais pour produire leurs propres informations sur leurs changements du travail et adapter leur organisation. Sur la base de ces résultats, nous avons réalisé 2 ateliers de conception d'outils avec leurs futurs utilisateurs. Nous avons identifié et décrit 28 concepts selon a- le moment d'utilisation (avant/ pendant les d'agriculteurs), b- leur fonction (ce que les outils devront faire), c- leur contenu (les informations fournies), d- les modalités d'utilisation (par qui et comment seront-ils utilisés) et e- leur support matériel. 4 prototypes ont été élaborés : une fiche technique informant des changements du travail, un quizz et un jeu permettant d'identifier des changements du travail pour une exploitation, et un carnet de suivi d'essai pour relever des informations clefs afin d'établir un bilan de la gestion des concurrences et des choix d'organisation. Nous proposons pour terminer une relecture critique de la démarche employée. Nous revenons sur l’intérêt et les conditions de réussite du diagnostic des situations d'usage et d’ateliers de conception. Le diagnostic a été essentiel pour développer une démarche de conception innovante qui va bien au delà d’une amélioration d'outils de simulation du travail existants.

In order to check the effects of the landscape’s composition on an agricultural landscape, an expert system has been created. The aim of this model is to generate realistic landscapes from information about the means of production of the agricultural enterprise inside the site of the study.A validation procedure has been created. An application of this procedure was realised on two kind of farms, one specialized in pig farming and another one specialized in cattle farming.We studied the relationship between the spatial and temporal evolution of a 2km² area and a landscape metric, the quantities of maize in a given neighbourhood, which is linked to the well-being of biodiversity.Our results show that the properties of a landscape don’t differ with the evolution of time: a landscape with given properties one year will remain the same on a whole with the passing of time. Moreover, a landscape’s dynamic won’t change depending of the portion we’re studying.; Afin d’évaluer l’influence de différentes structures paysagères sur un paysage agricole, un modèle décisionnel d’Allocation de cultures a été produit dans le cadre du projet AGRICONNECT par l’équipe INRA SAD Paysage. Sachant que l’objectif de ce modèle est de simuler des paysages réalistes, une démarche de validation des décisions d’assolements produites a été créée. A partir d’une exploitation en élevage porcin validé, nous avons généralisé son fonctionnement à l’ensemble d’un paysage de 2km² dont nous avons étudié l’évolution spatiale et temporelle ainsi que son impact sur une métrique paysagère d’intérêt biologique.L’application de la démarche de validation décrite, nous avons pu valider un cas d’exploitation.Nos résultats nous permettent de mettre en évidence une certaine homogénéité dans le fonctionnement des couverts des paysages issus d’exploitations porcines à l’échelle annuelle. De même, les propriétés du paysage ne varient pas suivant la portion étudiée.

Mixed crop-livestock farms are again attracting worldwide interest, as they are considered to be a good way to limit environmental problems while allowing a productive and economically viable agriculture. The incentives of the Common Agricultural Policy and decreasing workforce availability nevertheless marginalized these farms in Europe. This thesis aims at understanding the conditions for a survival of sustainable mixed crop-livestock farms. A partnership process with farmers, mayors and technical advisers has been led in a French less favoured area, the Coteaux de Gascogne. Our work has shown that even if a wide variability existed between farms, local mixed crop-livestock farming was a good trade-off compared to farm specialization concerning an environmental and economic sustainability. An analysis of farm past trajectories allowed us to enlighten four “paths to last” in mixed crop-livestock farming. Two of these ones appeared to be suitable paths to maintain mixed crop-livestock farms in a uncertain context: “maximizing autonomy” and “diversification of production units”. On the basis of these two types of trajectories, we have co-constructed with local actors two technical prospective scenarios. In line with the type “maximizing autonomy”, forage legume intercropping could enable to autonomously feed the bovine herd while maintaining soil fertility. In line with the type “diversification of production units”, fattening heifers would allow a commercialization through short circuit. These scenarios have been adapted and then simulated on local farms. This type of approach allowed to i) strongly involve local actors through collective meetings and ii) an original future study based on a retrospective study integrating long time changes., Les exploitations de polyculture-élevage sont de plus en plus reconnues au plan international comme limitant les problèmes environnementaux tout en permettant une agriculture productive et économiquement viable. Les incitations à la spécialisation de la PAC et la diminution de la main d’œuvre agricole les ont néanmoins marginalisées en Europe. Cette thèse vise à éclairer les conditions de maintien d’exploitations de polyculture-élevage durables. Un travail en partenariat avec des agriculteurs, maires et conseillers agricoles a été conduit sur un cas d’étude en zone défavorisée simple française, les Coteaux de Gascogne. Nos travaux ont montré que, malgré une forte variabilité entre exploitations, la polyculture-élevage locale était un bon compromis par rapport à la spécialisation pour une durabilité environnementale et économique. Une analyse des trajectoires passées des exploitations nous a permis d’éclairer quatre types de « chemins pour durer » en polyculture-élevage. Parmi ceux-ci, deux sont apparus pertinents pour le maintien de la polyculture-élevage en contexte incertain : « maximiser l’autonomie » et « diversifier les ateliers ». Sur la base de ces deux types de trajectoires, nous avons co-construit avec les partenaires deux scénarios techniques prospectifs. Pour le type « maximiser l’autonomie », implanter des intercultures fourragères basées sur des légumineuses permettrait de favoriser l’autonomie alimentaire du troupeau en maintenant la fertilité des sols. Pour le type « diversifier les ateliers », finir des génisses permettrait de les valoriser en circuit court. Ces scénarios ont été adaptés puis simulés sur des exploitations locales. Ce type de démarche a permis i) d’impliquer fortement les acteurs locaux via des réunions collectives et ii) une approche prospective originale fondée sur une étude rétrospective intégrant le temps long.