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International audience; Organic farming practices are a possible way to reconcile agricultural production and water quality, but the comparative merits of conventional and organic practices regarding the nitrogen (N) issue are complex and still being debated. This study was designed to investigate the choice governing conversion to organic farming of en experimental mixed dairy farm in Lorraine (eastern France) and to highlight the assoicated changes in N fluxes. The study was conducted over a suitably long period of time at a farm scale integrating the diversity of practices in one conventional and then two autonomous organic systems (a grazing livestock system and a mixed dairy system). Two indicators were used to draw up the main features. First, the farm-gate N budgets show the the organic farm has a balance twice as low as the conventional system. Second, the soil surface balance exhibited substantial differences between functional zones. Finally, this study shows that an accurate estimation of soil surface balance requires taking into account the spatial distribution within the farm area based on practices and their rationale.

ESSN: 1879-4246; International audience; Organic agriculture is a production system which relies on ecosystem management and ecological processes rather than on the external flow of agricultural inputs. The development of the organic sector has incluced a spatial decoupling of livestock and crop production. This has increased the flow of nutrients that occurs between farms compared to what happens within individual farms. Organic systems have replaced synthetic inputs with site-specific management practices to balance input and output nutrients to ensure short-term productivity and long-term sustainability. This paper addresses the nutrient management of mixed and specialized farming systems, with a special emphasis on the reliance on livestock production for the nutrient management of arable farmland. We assessed the nutrient budgets of nitrogen (N), phosphorus (P), and potassium (K) of 28 organic farms selected according to livestock density from three French countries. The farms were classified as stockless, mixed, and cattle farming systems. A soil surface nutrient budget was calculated for each farm based on inputs (N fixation, excreta, and manure) and outputs (grazing, offtake, harvests) on annual crops and grasslands. Inputs due to N atmospheric deposition and seeds and losses due to leaching and volatization were not considered in this study. Nutrient budgets of the 28 farms revealed N, P and K deficits, although disparities between farming systems and their geographical location were also observed. Stockless farms presented high N deficit whereas mixed and livestock farming systems presented lower deficits (close to equilibrium) or even surpluses in a county with a high density of livestock farms. Differences between farming systems in terms of P and K budgets followed the same trend, but regional specificities appreared significant in stockless and livestock systems (related to the size of farms and the stocking rate). None of the farms purchased off-farm organic fertilizers when exchanges of manures and straw were observed at the regional scale. When livestock is present on the farm, the nutrient resources came mainly from recycling internal resources (manures, excreta, and N fixation), whereas stockless farming systems purchased organic manure from neighboring farms ( 14 to 58 % of total N inputs, 10 to 100 % of total P and K inputs). The sustainability of stockless organic farming systems is questioned, noticeably those that were located in regions where resources of organic matter are scarce. Only farming systems producing large quantities of manure or which purchased feed showed balanced nutrient budgets.

National audience; Intercropping (the simultaneous growth of 2 or more species in the same field) is one way to solve some difficulties that organic supply chain has to face. The aim of this article is to assess the consequences and the compatibility with intercrops at 2 levels: i) cropping systems of 18 farmers from north of France and ii) the logistics ofagricultural cooperatives which collect durum wheat in Midi-Pyrenees altogether with two cooperatives that already had experimented intercrops (Terrena and AgriBioUnion).The conclusions of our work is that intercrops seem a priori compatible with farmers’ cropping systems and with the presentlogistic organization of cooperatives but the main difficulty remains the feasibility and the cost in sorting out grains. Constraints and benefits of intercrops must then be analyzed more precisely at each level of the supply chain in order to collectively develop solutions.; Les cultures associées (la culture simultanée d’au moins deux espèces sur une même parcelle)sont un moyen de répondre en partie aux difficultés rencontrées par les filières biologiques. L’objectif de cet article est d’identifier les conséquences de leur mise en œuvre ainsi que le degré de compatibilité au niveau : i) des systèmes de culture de 18 agriculteurs lorrains et ii) de l’organisation logistique des coopératives de Midi-Pyrénées collectant du blé dur et de deux coopératives ayant déjà expérimenté ces mélanges (Terrena et AgriBioUnion). Les conclusions de nos travaux montrent que les cultures associées sont a priori compatibles avec les systèmes de culture lorrains et avec l'organisation logistique actuelle des coopératives mais que le principal frein à leur développement réside dans la faisabilité et le coût du tri des grains. Les contraintes et bénéfices engendrés par les associations doivent donc être analysés plus finement et ce à chaque maillon de la filière afin de développer collectivement des solutions.

Depuis plusieurs décennies, l’évolution de l’agriculture en France est, dans un certain nombre de régions de grande culture et d’élevage marquée fortement par la simplification des assolements accompagnée d’un usage accru des intrants et la standardisation des itinéraires techniques. Le challenge est maintenant de concevoir des agroécosystèmes plus diversifiés dans l’objectif d’une gestion écologique des parcelles cultivées devant se traduire par une amélioration de la productivité et la stabilité des systèmes face à divers aléas et la fourniture de différents services éco-systémiques. Ce projet a exploré l’augmentation de la diversité cultivée au sein de la parcelle via des associations céréale-légumineuse. Il a montré la diversité des services que l’on peut en attendre en agriculture biologique et en agriculture conventionnelle, en système céréalier et en système d’élevage. Ces associations permettent de répondre à la fois à des enjeux de production, de réduction des intrants, de réduction des impacts environnementaux des cultures, de stabilité face à des aléas biotiques et abiotiques. Le coeur du projet a consisté a testé différents leviers d’actions pour aider à l’orientation des performances de ces associations pour différents objectifs. Les atouts et contraintes ’adoption à l’échelle des filières (notamment pour les collecteurs) ont été aussi mis en évidence et quantifiés., We have seen in the last decades in France a great simplification in crop successions in cereal farms and mixed farms with livestock with an increasing use of inputs and a standardization of crop management. The challenge is now to build more diversified agroecosystems through an ecological management of crop areas in order to increase yields and stability and to supply several ecosystemic services. This project has investigated the increase in crop diversity in space within the field through cereal-legume intercropping. Different services may be obtained in organic and conventional farming systems, in cereal and mixed farms with livestock. Intercropping can combine productivity, reduction of inputs, environmental impacts and stability against various biotic and abiotic constraints. Several practices have been tested in order to manage performance of intercrops for different aims. The advantages and constraints for different stakeholders such as collectors have been investigated and quantified.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; Intensive agriculture ensures high yields but can cause serious environmental damages. The optimal use of soil and atmospheric sources of nitrogen in cereal-legume mixtures may allow farmers to maintain high production levels and good quality with low external N inputs, and could potentially decrease environmental impacts, particularly through a more efficient energy use. These potential advantages are presented in an overall assessment of cereal-legume systems, accounting for the agronomic, environmental, energetic, and economic performances. Based on a low-input experimental field network including 16 site-years, we found that yields of pea-wheat intercrops (about 4.5 Mg ha−1 whatever the amount of applied fertiliser) were higher than sole pea and close to conventionally managed wheat yields (5.4 Mg ha−1 on average), the intercrop requiring less than half of the nitrogen fertiliser per ton of grain compared to the sole wheat. The land equivalent ratio and a statistical analysis based on the Price's equation showed that the crop mixture was more efficient than sole crops particularly under unfertilised situations. The estimated amount of energy consumed per ton of harvested grains was two to three times higher with conventionally managed wheat than with pea-wheat mixtures (fertilised or not). The intercrops allowed (i) maintaining wheat grain protein concentration and gross margin compared to wheat sole crop and (ii) increased the contribution of N2 fixation to total N accumulation of pea crop in the mixture compared to pea sole crop. They also led to a reduction of (i) pesticide use compared to sole crops and (ii) soil mineral nitrogen after harvest compared to pea sole crop. Our results demonstrate that pea-wheat intercropping is a promising way to produce cereal grains in an efficient, economically sustainable and environmentally friendly way.

International audience; Nitrogen is known to be the limiting factor of productivity in organic systems. In low-input organic, mixed-crop dairy systems (MCDS) at the Mirecourt INRA station, studies are conducted on the contribution of associated cereal/protein-rich plant crops and concentrate mixes to the nitrogen self-sufficiency of the system. An agronomic and zootechnical analytical trial was established with nine types of cereal and protein-rich plants, and associated cereal/protein-rich plant crops were compared in plot trials in 2006 and 2007. The valorization of three cereal/protein concentrate mixes by 24 lactating dairy cows was tested in a zootechnical experiment during winter 2007. Dairy cows were each fed 4 kg d-1 of the mix, 8kg DM d-1 of lucerne/cocksfoot hay, and permanent grassland hay ad libitum. Associated cereal/protein rich plant crops produced a greater and more stable yield (3.0 t ha-1) that pure cereals (2.2 t ha-1) but the proportions of protein rich grains in the mixes were highly variable (26 to 62%). Dairy cows' feed requirements were satisfied by the three diets. Cereal/protein concentrate mixes had a low impact on dairy cows' performance because of the high contribution of forages to the diet.