Vulnérabilité et adaptations des systèmes agraires à Madagascar aux changements climatiques : rapport technique final, 2007 - 2010

A Madagascar, le secteur agricole, dans lequel prédominent une agriculture essentiellement extensive, irriguée ou pluviale, ainsi que l’élevage extensif, reste encore fortement tributaire des aléas climatiques. De ce fait, les changements climatiques, qui se traduisent par d’importants bouleversements des régimes thermiques, pluviométriques et des phénomènes exceptionnels (tels que les cyclones) prennent une importance qui n’est pas encore suffisamment considérée dans les politiques de développement nationales. Face à cette situation, Madagascar a complété son Plan d’action national pour l’adaptation aux changements climatiques (PANA), se traduisant notamment par la publication des deux Communications Nationales. Cependant, les acteurs et décideurs impliqués dans l’exécution de ce plan sont encore loin de cerner la variation spatiale des différentes composantes de la vulnérabilité climatique, et ne disposent pas encore de suffisamment d’informations, outils et compétences pour mieux décider des actions à mener et des régions où ils doivent se focaliser. Ce projet visait à contribuer à ces informations, outils et compétences manquantes. Plus spécifiquement, il visait à catalyser des réflexions et un dialogue entre les acteurs du PANA et les chercheurs, à produire des informations spatialisées sur différents facteurs affectant la vulnérabilité et l’adaptation aux changements climatiques sur toute l’île de Madagascar, à mieux comprendre les stratégies d’adaptation existantes ou envisageables, à explorer diverses stratégies d’intervention sous différents scénarios ainsi qu’à renforcer les capacités nationales dans l’analyse de la vulnérabilité et l’adaptation aux changements climatiques. Le projet a été exécuté sur trois années par l’Université d’Antananarivo en partenariat avec l’Institut de recherche pour le développement (IRD), le Centre National de la Recherche Appliquée au Développement Rural (FOFIFA), l’École Supérieure des Sciences Agronomiques (ESSA), et l’équipe de coordination du PANA au Ministère de l’Environnement, des Eaux et Forêts

Field-specific difficulties for transplanted rice to cope with ammonia from a localized enriched environment

The objective of the study was to find some relationship between the location of rice fields in a typical valley of central Madagascar and the response of transplanted rice to nitrogen fertilizer. Comparison was made between lowland locations and plain location. High rainfalls are typically occurring during the periods of soil puddling and rice transplantation. As a consequence, it is difficult to manage nitrogen fertilization of the crop. To avoid nitrogen losses by runoff, urea deep placement (2 g urea-supergranules at 10 cm depth) was practiced. Probes attached to urea super-granules enabled to observe the dynamics of the ammonia derived from the fertilizer. These observations were performed in three fields (different location). The response of transplanted rice to nitrogen was weak in the lowlands, and rice performed badly in ammonia uptake. In the adjacent plain, the response was better and ammonia correctly assimilated. Ferrous ion toxicity and low phosphorus status are discussed as causes for the rice difficulty to benefit from an ammonia enriched environment in the lowland fields

Field-specific difficulties for transplanted rice to cope with ammonia from a localized enriched environment

The objective of the study was to find some relationship between the location of rice fields in a typicalvalley of central Madagascar and the response of transplanted rice to nitrogen fertilizer. Comparison was madebetween lowland locations and plain location. High rainfalls are typically occurring during the periods of soilpuddling and rice transplantation. As a consequence, it is difficult to manage nitrogen fertilization of the crop.To avoid nitrogen losses by runoff, urea deep placement (2 g urea-supergranules at 10 cm depth) was practiced.Probes attached to urea super-granules enabled to observe the dynamics of the ammonia derived from thefertilizer. These observations were performed in three fields (different location). The response of transplantedrice to nitrogen was weak in the lowlands, and rice performed badly in ammonia uptake. In the adjacent plain,the response was better and ammonia correctly assimilated. Ferrous ion toxicity and low phosphorus status arediscussed as causes for the rice difficulty to benefit from an ammonia enriched environment in the lowlandfields

Fertilité et gestion de la fertilisation dans les sytèmes maraîchers périurbains des pays en dévelopeement (intérêts et limites de la valorisation agfricole des déchets urbains dans ces systèmes, cas de l'agglomération d'Antananarivo (Madagascar))

PARIS-AgroParisTech Centre Paris (751052302) / SudocSudocFranceF

Phosphorus availability of a French thermally conditioned sewage sludge assessed by isotopic labeling techniques

National audiencePhosphorus in urban sewage sludge is a potential source of P for agriculture if it is plant-available. In that case it could be an alternative to mineral P fertilizers known as non renewable source. However, to manage TCSS it is necessary to have an accurate assessment of its P fertilizing value. This work aimed to assess and compare the plant availability of P in TCSS and triple superphosphate (TSP). A pot experiment with a mixture of ryegrass and fescue was carried out for 2 months on a P-deficient and slightly acidic soil in which 50 mgP.kg–1 was applied as TSP and TCSS. The 32P–labeling of soil P was used to accurately quantify the P taken up by plants from the different P sources and to evaluate interactions after applying P-TCSS on P taken up from soil. In parallel, soil incubations were conducted on the same treatments to analyze soil respiration and soil microbial dynamics. In comparison to the control (no P applied), shoot and root biomass productions, and plant P nutrition increased with TSP and TCSS application. The contribution of TCSS and TSP to plant nutrition was 55.2% and 55.7%, respectively and the relative agronomic effectiveness of TCSS was 64%. This decrease is explained by the carbon associated with the 50 mgP.kg-1 applied to soil. This carbon initiates a priming-effect with a high microbial activity marked by high soil respiration and high P content in microbial biomass which competed for plant-available P and delayed the root and shoot growth. As a consequence, P taken up from soil and TCSS decreased both. In conclusion, this study shows that it is possible to substitute TSP by TCSS