Systèmes de culture innovants : une nouvelle génération de réseau expérimental et de réseau de compétences

International audienceLes conseillers ou les animateurs agricoles doivent de plus en plus accompagner les agriculteurs dans un changement de pratiques et l’innovation, en particulier dans les suites du Grenelle de l’Environnement. Pour leur permettre, ainsi qu’à leurs responsables hiérarchiques, de faire évoluer le métier, une nouvelle intelligibilité de la relation de conseil et d’accompagnement du changement a été produite. Elle est issue d’échanges entre conseillers ou animateurs et chercheurs autour d’expériences vécues et d’analyse de leur activité réalisée par les chercheurs. Elle repose sur la notion clé de « formats ». Ces formats peuvent être institués (le tour de plaine « à chaud », la formation avec intervention d’un expert), en cours d’institution (e.g. la co-construction d’un système de culture, le tour de plaine « à froid ») et leur combinaison dans l’accompagnement du changement en cours de construction (e.g. pour l’animation sur une aire d’alimentation de captage, ou l’accompagnement d’un groupe vers l’atteinte d’un cahier des charges « Grandes Cultures Économes »). Des outils sont proposés pour analyser ce qui perturbe le travail du conseiller ou de l’animateur dans des situations nouvelles et être opérationnels dans la mise en œuvre de nouveaux formats en vue d’aider les agriculteurs dans la transformation de leurs pratiques

Systèmes de culture innovants : une nouvelle génération de réseau expérimental et de réseau de compétences

International audienceLes conseillers ou les animateurs agricoles doivent de plus en plus accompagner les agriculteurs dans un changement de pratiques et l’innovation, en particulier dans les suites du Grenelle de l’Environnement. Pour leur permettre, ainsi qu’à leurs responsables hiérarchiques, de faire évoluer le métier, une nouvelle intelligibilité de la relation de conseil et d’accompagnement du changement a été produite. Elle est issue d’échanges entre conseillers ou animateurs et chercheurs autour d’expériences vécues et d’analyse de leur activité réalisée par les chercheurs. Elle repose sur la notion clé de « formats ». Ces formats peuvent être institués (le tour de plaine « à chaud », la formation avec intervention d’un expert), en cours d’institution (e.g. la co-construction d’un système de culture, le tour de plaine « à froid ») et leur combinaison dans l’accompagnement du changement en cours de construction (e.g. pour l’animation sur une aire d’alimentation de captage, ou l’accompagnement d’un groupe vers l’atteinte d’un cahier des charges « Grandes Cultures Économes »). Des outils sont proposés pour analyser ce qui perturbe le travail du conseiller ou de l’animateur dans des situations nouvelles et être opérationnels dans la mise en œuvre de nouveaux formats en vue d’aider les agriculteurs dans la transformation de leurs pratiques

Integral formulation of null-collision Monte Carlo algorithms

International audienceAt the kinetic level, the meaning of null-collisions is straightforward: they correspond to pure-forward scattering events. We here discuss their technical significance in integral terms. We first consider a most standard null-collision Monte Carlo algorithm and show how it can be rigorously justified starting from a Fredholm equivalent to the radiative transfer equation. Doing so, we also prove that null-collision algorithms can be slightly modified so that they deal with unexpected occurrences of negative values of the null-collision coefficient (when the upper bound of the heterogeneous extinction coefficient is nonstrict). We then describe technically, in full details, the resulting algorithm, when applied to the evaluation of the local net-power density within a bounded, heterogeneous, multiple scattering and emitting/absorbing medium. The corresponding integral formulation is then explored theoretically in order to distinguish the statistical significance of introducing null-collisions from that of the integral-structure underlying modification

Oligodendrocyte differentiation is increased in transferrin transgenic mice

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Myelination and motor coordination are increased in transferrin transgenic mice

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Monte Carlo advances and concentrated solar applications

International audienceThe Monte Carlo method is partially reviewed with the objective of illustrating how some of the most recent methodological advances can benefit to concentrated solar research. This review puts forward the practical consequences of writing down and handling the integral formulation associated to each Monte Carlo algorithm. Starting with simple examples and up to the most complex multiple reflection, multiple scattering configurations, we try to argue that these formulations are very much accessible to the non specialist and that they allow a straightforward entry to sensitivity computations (for assistance in design optimization processes) and to convergence enhancement techniques involving subtle concepts such as control variate and zero variance. All illustration examples makePROMES - UPR CNRS 8521 - 7, rue du Four Solaire, 66120 Font Romeu Odeillo, France use of the public domain development environment EDStar (including advanced parallelized computer graphics libraries) and are meant to serve as start basis either for the upgrading of existing Monte Carlo codes, or for fast implementation of ad hoc codes when specific needs cannot be answered with standard concentrated solar codes (in particular as far as the new generation of solar receivers is concerned). (C) 2013 Elsevier Ltd. All rights reserved

Protection Intégrée des rotations avec Colza et blé tendre : Conception et évaluation multicritères d’itinéraires techniques économes en produits phytosanitaires

Le projet PICOBLE avait pour objectif, en se plaçant à l’échelle de l’itinéraire technique, de contribuer à la recherche de solutions permettant de réduire l’usage de produits phytosanitaires dans les systèmes de culture à base de colza et de blé. Il a permis de concevoir et de tester des ITK innovants pour différentes situations. Les résultats obtenus concluent à la possibilité d’une réduction des produits phytosanitaires de 30 à 40% sans affectation de la marge de l’agriculteur sur la base des hypothèses de prix prises, mais avec une réduction du volume de production de 10% pouvant affecter l’économie des filières avales. Les connaissances acquises permettent d’envisager de nouvelles pistes de réduction à plus long terme mais elles nécessitent encore un travail considérable, il faudra en particulier aborder des échelles plus larges au niveau du système de culture ou du paysage.Integrated protection of crop rotation with winter oilseed rape (WOSR) and winter wheat: Conception and multicriteria evaluation of pesticides saver cropping practices The PICOBLE project was looking for knowledge and knowhow likely to contribute to a reduction of pesticides use in wheat and WOSR-based rotations, at the scale of annual cropping practices. New cropping techniques have been imagined, discussed and tested in the field before being assessed with a multi-criteria approach. A 30-40% reduction of the total amount of pesticides is possible, without X. Pinochet et al. 244 Innovations Agronomiques 28 (2013), 243-256 affecting the farmer economic result under given price hypothesis, but with a 10% reduction of the production, that might affect the economic competiveness of the connected industries. Results and knowledge produced during the project open new perspectives for further reductions on the longer term. Nevertheless, work is still needed and approaches have to be extended to cropping systems and landscapes scales

An interdisciplinary approach to increase wheat within-field diversity and promote agro-ecosystem services

International audienceOne major challenge for increasing agriculture sustainability is to better mobilize crop genetic diversity, as prone by agroecology. A simple way to increase within-field diversity is to use cultivar mixtures, and this has been successfully applied to a few crops in the past. Despite numerous scientific papers documeting the value of cultivar mixtures in wheat and other cereals, especially to control diseases, their cultivation has remained marginal throughout the world. To understand the origin of this gap between scientific knowledge and agricultural practices, the French project Wheatamix explored the synergies mobilized by cultivar mixtures, their impact on various ecosystem services, and their potential to reinforce the sustainability, resilience, and multi-functionality of agriculture. It focused on the agro-ecological and socio-economic impacts of variety associations at different scales, from the plant level up to the wheat supply chain. The project aims at developing new blending and breeding methods to design performing mixtures.To understand how plant-to-plant interactions shape wheat mixtures performances, Wheatamix has set five objectives: 1) describe the variability of morphological and ecological traits in a panel of 57 varieties; 2) explore variability by blending 16 contrasted varieties from the panel into 72 mixtures, composed of 2, 4, and 8 components; 3) study the ecosystem services provided; 4) assess the technical and economic performances in farmer conditions; 5) evaluate the impact of cultivar mixtures on the wheat supply chain. To achieve these goals, this project has developed an interdisciplinary approach, mobilizing agronomy, ecology, economics, ecophysiology, epidemiology, genetics, and management sciences. The project brought together scientists from 10 labs, as well as agricultural advisers and farmers from 6 French counties. The project first described the functional diversity of 57 varieties, highlighting the effects of modern breeding on trait variability, that lowered variability of traits subject to direct selection, and impacted both plant architecture, physiological traits as nutrient absorption, but also trade-off between traits. Wheatamix then surveyed how variation in mixture diversity impacted wild communities. A first result highlighted the low abundance of macro-organisms in this experiment: no relationship was found between the number of varieties in a mixture and the diversity/abundance of earthworms, weeds, mycorrhizae, springtails, beetles, nematodes. However, a significant effect of mixture diversity on the abundance of some spiders, and on nitrifying bacteria, was observed. Coming to ecosystem services, disease regulation (rust and septoria) has been confirmed as the most strongly and positively affected by varietal associations, raising also the strong effects of architectural variability of the canopy (septoria). Diversity also contributed to higher predation rates on aphids. Lastly, soil nitrification and denitrification activities were significantly affected by mixture diversity on 4 surveyed sites, contributing to a shift in plant nutrition and positive effect of greenhouse gas emission.Co-design of variety mixtures was carried out with farmers, technical advisers, and scientists. For three years, 30 farmers in the Paris basin proposed varietal blends and measured their performance on their farms. This exchange first highlighted that the first goals for farmers was to i) secure their production ii) simplify plot management. Then co-design workshops allowed to propose assembly rules and design mixtures, resulting in a wide diversity of sown mixtures. Field trials revealed that in more than 70% of the cases, the mixture had a higher yield than the mean of its components. This work highlighted farmers needs and resulted in a Multicriteria Evaluation Tool, helping farmers and advisers to design mixtures. The survey of the wheat supply chain finally highlighted the need for a concerted innovation among the various actors. Finally, Wheatamix also developed new statistical method to infer mixing ability, allowing both to blend the best mixers, and also to propose new breeding methods.Coupling various disciplines and approaches, such as ecophysiological modeling of plant competition (FSPM WALTer), field and controlled experiments, theoretical framework in ecology (sampling vs complementarity effects, functional traits and tradeoff), and mixture co-design and surveys with stakeholders, Wheatamix has allowed to understand the interest of cultivar mixtures for farmers. Wheat cultivar mixtures are experiencing an exponential growth: they only represented 2% of bread wheat sown in 2010, and are presently at 8%, raking at the first position on the cultivar list. Wheatamix emphasizes the need for an interdisciplinary approach when addressing agroecological subjects, and illustrates the strong mutual benefices between agronomic and ecological sciences