Search

National audience; Evaluating cropping systems depends on the perspective and scale considered. An agronomic point of view is often considered with the assessment of the impacts of the cropping system at the field scale, or an economic point of view with the consequences of implementing a cropping system on the farm. Tools have been developed to enable a more integrative assessment of cropping systems. This is the case of the MASC (R) model which, using multicriteria evaluation, estimates the sustainability of cropping systems from environmental, economic and social perspectives. MASC-Mada was developed specifically for upland cropping systems in Madagascar. It has been used to compare conservation agriculture cropping systems with conventional cropping systems. The results, confronted to the opinion of farmers, show that conservation agriculture systems are generally more sustainable than conventional systems but a mixed system combining the use of cover crops and less frequent tillage would better take social and economic aspects into account.; L’évaluation des systèmes de culture de´pend du point de vue et de l’échelle envisagés. Un point de vue agronomique est souvent adopté avec l’évaluation des impacts de différents systèmes à l’échelle de la parcelle, ou un point de vue économique avec les conséquences d’un système de culture sur le fonctionnement de l’exploitation agricole. Des outils ont néanmoins été développés pour permettre une évaluation plus intégrative des systèmes de culture. C’est le cas du modèle MASC1 qui permet, par une approche multicritère, d’évaluer la durabilité des systèmes de culture à la fois d’un point de vue environnemental, économique et social. MASC-Mada, développe pour les systèmes de culture pluviaux à Madagascar, a été utilisé pour comparer des systèmes en agriculture de conservation avec des systèmes conventionnels. Les résultats des évaluations, confrontés aux points de vue des agriculteurs, révèlent que les systèmes en agriculture de conservation sont globalement plus durables que les systèmes traditionnels, mais qu’un système mixte alliant utilisation de plantes de couverture et des labours moins fréquents prendrait mieux en compte les aspects sociaux et économiques.

National audience; Vegetable production makes an intensive use of pesticides, and a major challenge is to build alternative cropping systems that can control pests and diseases with fewer uses of chemical products. An on-farm analysis was conducted in Southeast France to assess the efficacy of several cropping systems in simultaneously controlling two major pests: root-knot nematodes (Meloidogyne spp.) and lettuce drop due to Sclerotinia sclerotiorum. Ten cropping systems resulting from the combinations of three crop sequences and two alternative techniques, solarization and green manure, were assessed during two years. The use of solarization once a year or once every two years limited the occurrence of S. sclerotiorum. Sorghum green manure tended to increase S. sclerotiorum incidence; the effect was positively correlated with green manure duration. Especially when no vegetable was cropped in summer, the green manure crop duration was lengthened and this probably created soil conditions favorable to the development of the fungus. The incidence of root-knot nematodes was largely dependent on crop rotation: a melon crop in summer increased its incidence on the subsequent lettuce crops whereas a summer sorghum cover crop had no effect. The cropping systems that limited Sclerotinia development in soil tended to support the root-knot nematode populations. These results should motivate farmers and advisers to adopt a systemic analysis and take into account the various interactions among inoculum level, soil characteristics, crop rotations, and technical management options for designing sustainable vegetable production systems.

This research focuses on the prescription activity for the supervision of a horticultural company. This company is owned by a group of national producers, with around twenty permanent staff and around the same number of temporary staff during the peak season. In this organisation in which the work is not formalised, the organisation of the production is not always planned ahead and where everything is in flux (natural element, living products, industrial variability), it is impossible, even against counter- productive to try to pre-write everything.In this context, we consider that the supervisor is a designer who develops his activity based on the existing frameworks for action in the work situation. These frameworks are made up of pre-existing primary frameworks (natural and social) that he interprets using the resources that he has built up based on his experience and by interacting with colleagues. To organise the work to do and to be done, and to act efficiently, the supervisor will design the organisation and the prescription (during the action and by the action) by constantly facing the reality of the situation. Prescribing then comes down to designing activity frameworks (frameworks for behaving and frameworks to drive behaviours) by simultaneously driving daily and occasional micro-projects as well as design sequences with differentiated temporal spans. During the design process of the prescription, the supervision therefore transforms primary frameworks in secondary frameworks, resulting in a succession of transformed frameworks some of which may crystallise in the form of artifacts (materialised or oral). We show that for this to happen, the supervisor conducts framing actions (daily microprojects) and re-framing actions (occasional microprojects) and of co-framing (occasional microprojects and design sequences). From this perspective, the prescription activity leads to a stratification of policy frameworks. And it requires not only complex design activities, but also and above all, real creativity of action on the part of the supervisor., Cette recherche porte sur l’activité de prescription de l’encadrement de proximité d’une entreprise horticole appartenant à un groupement de producteurs national. Celle-ci compte une vingtaine de permanents à l’année et accueillant autant de saisonniers durant la pleine saison. Dans cette structure où le travail est peu formalisé et l’organisation de la production pas toujours planifiée en amont, et dans un environnement où tout bouge tout le temps (élément naturel, produits vivants, variabilité industrielle), il est impossible, voire contre-productif de vouloir tout pré-écrire. Dans ce contexte, nous considérons que l’encadrant est un concepteur qui développe son activité en s’appuyant sur des cadres pour l’action préexistants dans la situation de travail et composés en partie de cadres primaires (naturels et sociaux) qu’il interprète, grâce à des ressources qu’il s’est construit sur son expérience, et en interagissant avec ses collègues. Pour organiser le travail à faire et à faire faire, et pour agir de manière efficace, l’encadrement va concevoir de l’organisation et de la prescription, dans et par l’action, en se confrontant en permanence à la réalité de la situation. Prescrire revient alors à concevoir des cadres d’action (cadres pour agir et cadres pour faire agir) en conduisant en simultané des microprojets quotidiens et des microprojets occasionnels ainsi que de séquences de conception, aux empans temporels différenciés. Lors du processus de conception de la prescription, l’encadrement transforme donc les cadres primaires en cadres secondaires, aboutissant ainsi à une succession de cadres transformés dont certains peuvent se cristalliser sous la forme d’artefacts (matérialisés ou oraux). Nous montrons que pour ce faire, l’encadrant procède à des actions de cadrage (microprojet quotidiens), de recadrage (microprojets occasionnels) et de co-cadrage (microprojets occasionnels et séquences de conception).Vue sous cet angle, l’activité de prescription aboutit à une stratification de cadres d’action. Et elle requiert non seulement une activité de conception complexe, mais aussi et surtout, une réelle créativité de l’agir de la part de l’encadrement.

Nitrogen management in cropping systems must face strong challenges. Substantial progress has been made in understanding the dynamics of nitrogen requirements for diverse crops, the determinants of immobilization and mineralization of nitrogen from organic matter in the soil, and the factors explaining the variability in the use efficiency of nitrogen fertilizers. This knowledge has been integrated in decision-making support tools for nitrogen fertilization as well as in monitoring tools. Such tools aim at satisfying crop nitrogen requirements throughout the crop cycle in order to maximise growth but often lead to periods of excess nitrogen nutrition. More recent knowledge on the effects of temporary nitrogen deficiencies make it possible to reflect upon new paradigms for nitrogen fertilization management. They involve the concept of useful nitrogen deficiency based on the objective of maximizing nitrogen efficiency as a fertilizer and thus minimising environmental losses. Finally, other levers than nitrogen fertilization can be mobilized to take the above mentioned challenges in nitrogen management into account and enlarge the question to the landscape scale.

OCL 2010, 17 (5) : Dossier Les complémentarités oléagineux/protéagineux (agronomie, nutrition); National audience; For the last forty years oilseed and high-protein crops have undergone important changes in terms of area and localisation in France. On the Seine basin example, we show that the specialisation of the farming systems and the agricultural regions has strongly changed the cropping patterns by reducing grasslands which were replaced by a constant increase of the wheat area in a one hand and by a dramatic increase, from the eighties, of the rapeseed, field pea and sunflower areas in another hand. Then from the nineties, rapeseed has gradually replaced field pea and sunflower, the areas of which have fallen. The decrease in the number of cultivated species has led to a clear trend to the simplification and the shortening of the crop successions: short crop successions based on rapeseed (as rapeseed-wheat-barley or rapeseed-wheat-wheat) and cereal successions (as wheat-wheat-wheat, wheat-wheat-barley or wheat-barley-barley) have strongly increased on the Seine basin over the last twenty years. The crop succession shortening, that causes crop protection problems towards weeds, insects or diseases, is only possible in relation with an intensive use of pesticides: thus the increase of the rapeseed area is positively correlated with the increase of the average number of plant pest controls, especially with herbicides. These agricultural dynamics have negative impacts on environment and enhance the economical risks the farms have to cop with. As a consequence, a new crop diversification, supported by policy-making and agricultural production networks, seems to be a strong future issue

À partir d'un dispositif de recherche à échelles emboîtées, de l'exploitation agricole à la région, cette étude analyse la diversité des agroécosystèmes, la place des céréales traditionnelles (mil, sorgho) dans les assolements et l'évolution des systèmes de culture et des pratiques dans les exploitations. En fonction des échelles d'observation, la place des différentes cultures varie. À l'échelle régionale, le sorgho reste une culture importante à travers l'extension de son aire de culture et la surface cultivée par actif. Au niveau des exploitations, l'évolution des systèmes de culture est marquée par leur diversification. La place du sorgho diminue et cette régression ne s'explique plus uniquement par le développement du maïs car le mil aussi se développe. Le mil contribue maintenant davantage à la formation des revenus des exploitations et sa culture commence à s'intensifier par le recours aux engrais. La diminution de la taille des soles de sorgho et l'augmentation continue du mil peuvent contribuer, selon les choix des agriculteurs, au maintien ou à la diminution de la diversité variétale.

National audience; Dans la région de Tombouctou au Mali, les sécheresses des années 1970-80 et la rébellion touarègue des années 1990 ont entraîné la sédentarisation de populations nomades et le développement de l’agriculture. Afin de mieux connaître ces transformations, l’ONG Vétérinaires sans frontières a lancé une série d’études au démarrage d’un nouveau projet d’appui aux organisations agropastorales. L’évolution du système agraire d’une fraction arabe, fixée sur les bords du fleuve Niger, a ainsi été analysée. Trois systèmes de production ont été caractérisés. Les agropasteurs transhumants (20 p. 100 des familles de la fraction) sont sédentarisés sur la frange fluviale. Ils cultivent du riz et du bourgou dans les plaines inondables et possèdent des petits cheptels de ruminants, insuffisants pour satisfaire l’ensemble des besoins de la famille. Les pasteurs nomades (74 p. 100) sont toujours spécialisés en élevage et ont conservé un mode de conduite pastoral reposant sur la mobilité des troupeaux et des familles pour mettre en valeur des parcours sahéliens. Enfin, des agropasteurs semi-nomades (6 p. 100) combinent la vie de sédentaires en saison sèche, sur le site de fixation au bord du fleuve, et le nomadisme en saison des pluies, les travaux des champs étant alors assurés par des salariés. L’étude des relations agriculture élevage et de l’usage des ressources permet de discuter les politiques de développement centrées sur l’intensification agricole sur la frange fluviale.

Fodder resources provide the principal sources of feeds throughout the humid and sub-humid, arid and semi-arid and Mediterranean regions. They include grasses and legumes, and fibrous crop residues (FCR). Browse is another important source of fodder. The availability and use of the fodder resources is dependent on type of agroecosystem (e.g. humid and sub-humid to arid and semi-arid), cropping patterns and their intensity, type and concentration of animal species, and prevailing animal production systems. The productivity of ruminants is dependent on the potential of a feed to supply, through microbial degradation, balanced nutrients for production; digestible dry matter intake is highly correlated with animal productivity with individual feeds. Nutritive value relates to the capacity of a feed to supply nutrients to meet productive functions, and this is contingent on maximizing voluntary feed intake, potential digestibility, protein:energy (P/E) ratio, and availability of bypass nutrients, particularly proteins. FCR form the main base in feeding systems for ruminants throughout the tropics and the Mediterranean region, and in recent years considerable progress has been achieved in their use. A number of technologies can be applied singly or in combination: treatment with alkalis to increase digestibility, supplementation to improve overall digestion and provide balanced nutrients, use of bypass nutrients, and large scale on-farm application to demonstrate economic profitability. Supplementation is central to effective utilization and includes the use of multi-nutrient block licks (MNBL), non-protein nitrogenous sources, and a variety of leguminous forages like Acacia spp., Gliricidia maculata, Leucaena leucocephala and Prosopis juliflora. Given the advances that have been made on the use of FCR, extending known technologies through on-farm testing and demonstration far outweighs the need for further research on the effects of pre-treatments or supplementation. Such effort must involve strategies for more effective use of the fodder resources, especially in large scale participatory on-farm situations. These need to address efficiency in integrated natural resource use, the totality of production-post-production-consumption systems, and demonstration of more sustainable animal production systems.