New insights on nematode management on bananas in the french Caribbean

Given the increasing societal demand for more eco-aware farming practices during the last decade, considerable changes and innovations have already occurred in banana cropping systems worldwide, from the former concept of Integrated Pest Management (IPM) that relied heavily on the use of chemical control towards a more sustainable concept of Integrated Crop Management that favours non-chemical pest management. These innovative methodologies were particularly more rapidly adopted in countries where environment, health and safety conditions were politically prioritized. But there are also additional causes to this rapid transformation for designing more sustainable cropping systems, i.e. economical endowments, environmental policies, and retailing chain requirements. In the French West Indies, the reduction of pesticide impact on air, soil and water quality is a major goal of agronomy research. As a result, management approaches that combine different tools for pest management such as use of improved fallows, crop rotations, replants with banana vitroplants, resistant cultivars are discussed in relation with the different banana cropping systems. As an example, alternate cropping of bananas, pineapple or sugarcane combined with appropriate horticultural practices (chemical destruction of former banana plants, weeding during fallow) have already eradicated the burrowing nematode Radopholus similis from some areas in Martinique. In addition, some forage crops (Brachiaria spp.) or leguminous cover crops (e.g. Crotalaria spp., Neonotonia wightii) may be used in intercrop to remove or decrease under threshold level some other key-pests (e.g. lesion nematodes Pratylenchus coffeae, spiral nematodes Helicotylenchus multicinctus and root-knot nematodes Meloidogyne spp.) from soil. However, the adoption of these innovative practices strongly depends on the farming contexts and an evaluation of these innovations using crop models might be useful tools to help researchers and stakeholders. (Texte intégral

Model based evaluation of cover crops for banana cropping systems

There is actually a surge for reintroducing biodiversity in agricultural systems in order to reduce chemical inputs, suppress pests, and close biogeochemical cycles. The use of cover-crops is a promising way to reintroduce biodiversity into the fields. Cover-crops have the potential to decrease chemical use against weeds (by competition) and pests (by increasing in natural enemies). To decrease herbicide use, suitable plants must be able to grow in appropriate conditions, to do not compete the cultivated crop for nutrients or water, but should compete weeds for light and space. There is a trade-off between these objectives. Banana is a semi-perennial crop, each plant develops at its own rhythm leading to an unsynchronized plant population in three years; canopy and nitrogen demand of the crop follow this unsynchronized pattern. Banana cropping systems remain based on bare soil management and a large amount of herbicides is used. In tropical environment, the growth of weeds and cover-crop is complex because it is not constrained by seasons; a constant growth is possible due to relatively constant climate. In these conditions, variation in radiation due to canopy closure is one of the major drivers of their growth. We developed a model based method to assess the suitability of cover crop for a given cropping system context. This method first relies on early measurements of cover crop performed on the field. Then, we used a simulation model to contextualize the growth of cover crops and to assess their capacity to control weeds, to compete the cultivated plant, and to sustain on the long term under the shade of the main crop. This approach allows an early selection of cover crops that should be tested in real intercropping in the field. We present results of this evaluation for 11 species intended to banana intercropping. (Texte intégral

Management of banana nitrogen fertilization : taking into account nitrogen from organic origin

Les règles de fertilisation azotée en bananeraie prennent rarement en compte l'azote fourni par la minéralisation de la matière organique du sol ou des résidus de culture. Les résultats d'une expérimentation comparant différentes doses d'azote montrent qu'à partir d'un niveau de fertilisation azotée inférieure aux recommandations établies sur la base des prélèvements par la culture il n'y a plus d'augmentation du rendement. Ceci suggère que l'azote des engrais n'est pas la seule source d'azote pour le bananier et l'existence d'une offre d'azote non prise en compte dans la fertilisation conventionnelle. La matière organique du sol fourni des quantités d'azote minéral très variables en fonction du type de sol. Dans les andosols d'altitude des Antilles, les quantités d'azote issues de la minéralisation de la matière organique du sol couvrent une partie importante des besoins du bananier. L'utilisation d'un modèle simulant la dynamique des restitutions organiques et de l'absorption d'azote par le bananier (SIMBA) permet de définir des stratégies de fertilisation garantissant la satisfaction des besoins du bananier tout en limitant les pertes d'azote par lessivage. (Résumé d'auteur

La gestion de la fertilité dans les systèmes de culture du bananier-plantain dans le Sud-Ouest du Cameroun

Cette étude est localisée dans le sud-ouest du Cameroun. Elle mobilise agronomes et économistes sur un diagnostic des facteurs qui déterminent la gestion de la fertilité dans les systèmes de culture du plantain. Dans un premier temps, les auteurs présentent le contexte agroécologique et spatio-économique de la zone étudiée et analysent les questions que pose la fertilité pour la conduite de la culture du plantain. Dans un deuxième temps, l'analyse des modes de gestion de cette ressource montre en quoi l'épuisement de la fertilité des sols forestiers se traduit par un changement du système de culture et une baisse de la productivité du travail, sans une intensification en intrants des systèmes de production. La nécessité d'intégrer l'étude des contextes agroéconomiques dans l'analyse des questions de fertilité est alors posée comme un élément d'orientation de la recherch

Evaluation de plantes de couverture pour les vergers à la Martinique

de vergers comme le choix le plus pertinent pour la gestion de l'enherbement. Outre les avantages de lutte anti-érosive, ou encore de maintien de la perméabilité du sol dans des zones à forte pluviosité, la plante de couverture choisie doit posséder un certain nombre de qualités comme la rapidité d'établissement, le faible niveau d'entretien qu'elle demande à l'agriculteur, et une concurrence tolérable avec la culture principale. L'étude du comportement de 24 plantes de couverture, graminées et légumineuses, en conditions non limitantes, a permis d'en déterminer les principales caractéristiques agronomiques: vitesse de recouvrement du sol, biomasses produites foliaire et racinaire, surface foliaire massique, hauteur du feuillage, profondeur d'enracinement, analyse minérale du feuillage, et phénologie. L'aptitude à la repousse du feuillage après un fauchage est également observée. Une large gamme de résultats permet de sélectionner le couvert en fonction de l'objectif à atteindre. Sont encore à déterminer la pérennité de ces couverts face aux adventices, et la concurrence exercée vis-à-vis de la plante principale. (Texte intégral

Effects of clay microstructure and compost quality on chlordecone retention in volcanic tropical soils: consequences on pesticide lability and plant contamination

The scientific and economic context of our study is related to the pollution of the soils, fresh and marine water by a persistent organochlorine pesticide (chlordecone) in a tropical context (French West Indies). The former application of chlordecone results today in a diffuse pollution in agricultural soils, which are sources of contamination for cultivated roots, tubers, vegetables and terrestrial and marine ecosystems. Chlordecone is a very though and stable molecule (considered as a POP), it is mainly present in solid phase and has a strong affinity with organic matters. To prevent consumers and ecosystems exposure, it is thus necessary for us to evaluate the factors that influence chlordecone migration in the environment. In our research, we studied the impacts of clay microstructure on the chlordecone retention, comparing allophanes (amorphous clays present in andosols) and halloysite clays (type 1/1). We showed that allophane aggregates had a greater ability to trap chlordecone mainly due to their fractal structure. We also measured the effects of added composts on soil microstructure and on chlordecone lability and transfer rate from soil to plant 3 and 6 months after incorporation. The intensity and persistence of these effects were related to the initial quality and richness of the added composts. (Résumé d'auteur