-Introduction. Mango-based orchards in Senegal occur in a large diversity of cropping systems, but few typologies of these systems exist and none are associated with their comprehensive and quantitative analysis. In this study we defined and characterized the typology of these systems based on a quantitative assessment of their planting design, management, vegetative state, hedgerow structure and infestation by a major pest of mango, the Bactrocera invadens fly. Materials and methods. Multivariate analysis and clustering methods were applied to data from 64 mango-based orchards and their surrounding hedgerows sampled in the Dakar and Thiès regions, in Senegal. Results and discussion. Four types of cropping systems were identified according to orchard design and management patterns: (1) 'No-input mango diversified orchards', (2) 'Low-input mango orchards', (3) 'Medium-input citrus-predominant orchards' and (4) 'Medium-input large mango-or citrus-predominant orchards'. Orchard characteristics varied among these patterns. For instance, vegetation was dense and homogeneous in system 1, and the mortality rate of trees was high in system 2 but low in system 3. Orchards of systems 3 and 4 were mostly associated with hedgerows with, respectively, boundary-marking and defensive species. Lastly, the number of B. invadens flies was high in orchards of system 4, whereas it was low in those of system 2. Conclusion. The diversity of mango-based cropping systems in Senegal is now well described and quantified. This characterization is a preliminary step that is essential for further studies aiming to improve these systems.Senegal / Mangifera indica / fruit trees / orchards / typology / design / crop management / Bactrocera invadens / hedges / multivariate analysis Vergers à base de manguiers au Sénégal : diversité des modèles de conception et de gestion.
While pesticides help to effectively control crop pests, their collateral effects often harm the environment.On the French island of Reunion in the Indian Ocean, over 75% of the pesticides used are herbicidesand they are regularly detected in water. Agri-environmental models and pesticide risk indicators canbe used to predict and to help pesticide users to reduce environmental impacts. However, while thecomplexity of models often limits their use to the field of research, pesticide risk indicators, which areeasier to implement, do not explicitly identify the technical levers that farmers can act upon to limitsuch transfers on their scale of action (the field). The aim of this article is to contribute to developinga decision support tool to guide farmers in implementing relevant practices regarding the reduction ofpesticide transfers. In this article, we propose a methodology based on classification and regression trees.We applied our methodology to a pesticide risk indicator (I-PHY indicator) for identifying the importanceof the variables, their interactions and relative weight in contributing to the score of the indicator. Weapplied our methodology to the assessment of transfer risks linked to the use of 20 herbicides appliedto all soils in Reunion and according to different climate, plot management and product applicationscenarios (4096 scenarios tested). We constructed regression trees which identified, for each herbicideon each soil type, the contribution made by each input variable to the construction of the indicator score.The tree is represented graphically, and this aids exploration and understanding. The 20 herbicides weredivided into 3 groups that differed through the main contributing variable to the indicator score. Thesevariables were all technical levers available to farmers to limit transfer risks. These trees then becomedecision support tools specific to each pesticide user, enabling them to take appropriate decisions witha view to reducing pesticide environmental impacts. (Résumé d'auteur
Introduit à Madagascar au début du 19e siècle, le giroflier est originaire des îles Moluques en Indonésie. Malgré la sensibilité de l’essence aux risques météorologiques, tels les cyclones, et aux attaques d’un parasite local, andretra, et malgré la production variable de clous de girofle d’une année sur l’autre, son adaptation aux conditions écologiques de la côte Est de Madagascar, notamment dans la région d’Ana- lanjirofo, est remarquable. Très vite adoptée par les paysans (certains venus s’installer mais la plupart autochtones), ceux-ci l’ont intégrée dans leurs systèmes de culture en complément aux cultures vivrières (riz, surtout) et de rapport (café et vanille). Aujourd’hui, le marché du clou de girofle est une source de revenus réguliers pour les ménages et leur assure la sécurité ali- mentaire. Le giroflier donne deux produits de grande valeur économique, le clou de girofle, le bouton floral séché, et l’huile essentielle de girofle produite par distillation des feuilles, dont Madagascar est le premier exportateur mondial. Avec la vanille, les produits du giro- flier représentent les premiers produits agri- coles d’exportation, parfois les deuxièmes, de Madagascar. Les clous de girofle s’exportent surtout en Indonésie, où ils entrent dans la fabrication d’une cigarette locale appelée kre- tek. Un petit volume s’exporte vers les pays du nord sous forme d’épice. L’huile essentielle de girofle est distillée dans une multitude d'alam- bics rudimentaires dans toute la région de pro- duction. La qualité de l’huile essentielle dépend de sa teneur en eugénol, molécule mise en œuvre dans de nombreux secteurs éco- nomiques, dont l’industrie des cosmétiques, la pharmaceutique humaine et vétérinaire et l’in- dustrie alimentaire. Le giroflier de Madagascar semble représenter un exemple d’intégration réussie d’une nouvelle culture dans un système de cultures existant. Cependant, les plantations de girofliers vieillissent et les conditions de leur renouvellement ne sont pas pleinement pré- sentes. Alors que le marché du clou de girofle dépend fortement de la demande indoné- sienne, les perspectives sont prometteuses sur le marché mondial des épices et des produits contenant de l’eugénol. De ce fait, les pratiques actuelles et les possibilités d’adaptation et de développement du secteur Malgache de la girofle doivent être étudiées de près pour assu- rer l’équilibre futur entre les marchés et les besoins des paysans en termes de gestion de la ressource et de sa valorisation.
Latex is a key product for many tropical countries, of which 80% is produced by smallholders. Latex is produced by the rubber tree (Hevea brasiliensis). Given the 7-year immature unproductive period, establishing a rubber plantation requires considerable investment by smallholders, emphasizing the need for sustainable management. The difficulty of performing an agronomic diagnosis of a tree crop is to obtain an accurate picture of current and past cultivation practices, to be able to assess their impacts on the agro-ecosystem as well as on sustainability. Smallholders do not usually keep records of latex yield or of their technical practices, making it impossible to perform a diagnosis based on productivity. As latex harvesting involves tapping the bark, which leaves scars on the trunk, we hypothesised that these morphological traces would be good indicators of current and past practices and would thus enable a diagnosis based on the economic lifespan of plantation. To this end, we formalised a tapping panel diagnosis that involved reproducing the scars on tapping panel diagrams, and analysing them using two indicators: the amount of virgin bark consumed and the number of tapping years that remained. We validated this tapping panel diagnosis in a sample of 25 smallholder plantations in Cameroon, where we characterised eight tapping management systems reflecting different levels of tapping intensity. The assessment of the respective share of each tapping practice on virgin bark consumption revealed major effects of tapping frequency and of shaving thickness. We showed that the tapping panel diagnosis used as a decision support tool can increase remaining tapping years by 33% to 355%. To conclude, the tapping panel diagnosis formalised here for the first time will be a useful support for the participatory development of innovating tapping management schemes involving both technicians and smallholders. (Résumé d'auteur
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