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Soil tillage and cover crops impact spontaneous vegetation in agrosystems. Soil tillage destroys seedlings and can affect the soil seedbank. Cover crops compete with naturally occurring spontaneous species. Our aim was to gain insight into how soil tillage (here, the false seedbed technique) and cover crops impact the spontaneous vegetation in fallows preceding banana crops. In a fallowed field in Guadeloupe (French West Indies), two factors were combined in a split-plot design: the soil tillage modality before cover crop sowing (with or without the false seedbed technique) and the cover crop species (Crotalaria spectabilis, Pueraria phaseoloïdes, a 50/50 mix of Brachiaria decumbens + Brachiaria ruziziensis, a spontaneous vegetation control). On a monthly basis, in three permanent quadrats per sub-plot, all spontaneous species were identified and their numbers counted, while calculating the species richness and Shannon's diversity index. The spontaneous vegetation dynamics contrasted depending on the treatment. From 7 months post-sowing the species density, richness and Shannon index were significantly lower in treatments with B. decumbens + B. ruziziensis and P. phaseoloïdes, while in treatments with C. spectabilis, the species density and richness were significantly higher with than without the false seedbed technique. These effects were probably related to differences in the competitive ability of the cover crop used and, to a lesser extent, to the false seedbed effects on the soil seedbank. This is the first study to show that under a tropical climate, sown cover crop species combined with different soil tillage modalities have substantial impacts on the species density, richness and diversity of the spontaneous plant community over a 1-year period. These results could help farmers in their weed control strategies by providing them with a deeper understanding of the effects of practices on the spontaneous plant community.

The limitations of conventional farming systems become apparent when confronted with the challenges of sustainability. Conventional agricultural practices tend to degrade soil fertility and result in environmental damage and health risks through their various activities, including tillage, water use and management, and the use of fertilizers and pesticides, thus making these practices no longer acceptable from the economic and social points of view. CIRAD and its partners are therefore working on an agroecological transition founded on new ecological intensification practices that primarily consist of the elimination of tillage to help revive the soil’s biological activity, use of cover crops to boost nutrient recycling and the organic-mineral management of crops, maintenance of a permanent cover to improve water efficiency and to control erosion, and the recourse to biological control (functional biodiversity and cropping practices) of pests to limit the damage caused by them. Implementing these practices implies reviewing cropping system design methods and processes to better integrate the dimensions of actors, space, and time. It is indeed essential to involve or engage producers and other local actors in a more comprehensive manner, take different levels into account (cropping systems, production systems, markets, global changes, land use, etc.) as well as the temporal aspects of this agroecological transition, promote trajectories of progressive adaptation, and envisage modalities of providing support to actors. This process can give rise to technical solutions that can help enhance the sustainability of agricultural production systems.

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; Nematodes are major pests for crops, including banana. Environmentally friendly methods for managing plant-parasitic nematodes have to be developed, such as organic material application. Our study focuses on the impacts of several organic amendments on banana plants, considering mainly their effect on soil nitrogen supply and soil microbial biomass, and the consequences on plant-parasitic nematode impacts on the plants. A microcosm experiment for 13 weeks was conducted to evaluate four organic materials: sugarcane bagasse, sugarcane sludge, plant residues, and sewage sludge, compared to a control without organic amendment. Input of organic materials led to an important change on nitrogen resource, and plants grew better when the N availability was the highest, but better growth conditions did not necessarily reduce parasitic nematodes impacts on the roots. Damage on the roots depended on plant-parasitic nematode abundance. Three of four tested amendments exhibited a regulator effect on plant-parasitic nematode populations (bagasse, sugarcane sludge, and plant residues). Root growth was not the explanatory factor for this regulation. Only sugarcane sludge led to an overall positive effect on the plant, increasing its growth and reducing its parasitism pressure. The other organic materials exhibited an antagonism between the promoted plant growth and the reduced nematode populations.

1 The banana weevil Cosmopolites sordidus Germar (Coleoptera: Curculionidae) is the most serious pest of banana and plantain in most production areas, including the West Indies. 2 During a period of 2 years, we assessed the efficacy of a pheromone masstrapping control strategy of C. sordidus in field conditions in Guadeloupe at different cropping stages, both in sanitation fallows and in different ratoon banana crops. 3 In the fallows, catches peaked 3 months after beginning trapping and then decreased to zero after 9 months. By contrast, for the new plantations, the catches of C. sordidus increased after the 11th month and, in the older banana fields, there was no decrease in C. sordidus catches. The C. sordidus catches increased in the neighbouring banana plots, whereas they decreased in the fallows, and these catches decreased with the distance from fallow. 4 In conclusion, mass trapping with synergized pheromone traps within fallows should allow better sanitation of banana plantations. Yet, within the farms, fallows must not be located next to new plantations to avoid massive damage to the young plants. More generally, the present study emphasizes that the control of this insect should be managed at the farm scale and not at the field scale, with special attention being paid to the location of fallows. (Resume d'auteur)

Introduction. Aux Antilles francaises, les planteurs considerent generalement qu'il est necessaire d'effectuer periodiquement un travail du sol pour regenerer la porosite du sol et maintenir un fort rendement. Cependant, dans les bananeraies perennes d'altitude, le sol qui n'est jamais travaille presente de meilleures proprietes physiques et biologiques que dans bananeraies conduites de maniere conventionnelle. Pour determiner si le travail du sol avant la plantation est necessaire au bon fonctionnement d'une culture de bananiers et pour evaluer l'effet du labour sur la qualite du sol, une plantation de bananiers apres travail du sol classique a ete comparee a la plantation directe de bananiers sur un paillis de residus de recolte en parcelle experimentale. Materiel et methodes. La qualite du sol a ete evaluee par des indicateurs tels que la porosite, le statut organique, la biomasse microbienne et la structure des populations de nematodes. Le fonctionnement de la culture a ete evalue par la croissance de la plante, la distribution des racines, et la disponibilite de l'eau et de l'azote du sol. Resultats. Nous avons constate que le travail du sol a reduit la biomasse microbienne du sol et le nombre de guildes fonctionnelles de nematodes. Le travail du sol a eu seulement un effet a court terme sur la porosite du sol et n'a pas permis un enracinement plus profond. Bien que la mineralisation de l'azote organique du sol ait ete plus elevee avec le travail du sol conventionnel, la nutrition en azote des bananiers n'a pas ete meilleure, probablement parce que la fertilisation azotee elevee a compense les variations de la disponibilite de l'azote d'origine organique. Nous avons constate que la croissance des bananiers etait meilleure dans le traitement sans travail du sol. Cela a pu etre explique par un plus faible dessechement du sol du au paillis de residus de recolte laisse sur la surface du sol pour le traitement sans travail du sol. Conclusion. Par rapport au travail du sol classique, une plantation sans labour a ameliore la qualite du sol et les performances de la culture.

International audience; Farmers are inundated with advertisements about many innovations that are supposed to increase their yields or reduce environmental impact. However, the benefit of these innovations depends on the farming context. Here we present the ad hoc adaptation of the crop model SIMBA and a method to evaluate 16 innovations in six types of farms previously selected through a typology of the banana farming systems in Guadeloupe. The innovations include regulation of pesticide use, rotations and fallows, intercropping, conditional application of pesticides, resistant cultivars, and integrated systems. Our results show that, for a given innovation, the yield and pesticide reduction vary widely with different farm types. We show that environmentally friendly innovations often cause a greater decrease in yield in more productive farm types. Nevertheless, despite an apparent trade-off between yield and pesticide use, some innovations address both production and environmental issues, e.g., rotation with fallows improved with cover crops, regular fallows, and rotations with pineapples for the most intensive farm types. Our modelling study confirms the importance of innovation-farm type interactions and the usefulness of models for assessing large numbers of technological innovations among a wide range of biophysical and technical contexts.

Banana plantlets (Musa acuminata cv Grande Naine) cultivated in hydroponics take up silicon proportionally to the concentration of Si in the nutrient solution (0-1.66 mM Si). Here we study the Si status of banana plantlets grown under controlled greenhouse conditions on five soils developed from andesitic volcanic ash, but differing in weathering stage. The mineralogical composition of soils was inferred from X-ray diffraction, elemental analysis and selective chemical/mineralogical extractions. With increasing weathering, the content of weatherable primary minerals decreased. Conversely, clay content increased and stable secondary minerals were increasingly dominant: gibbsite, Fe oxides, allophane, halloysite and kaolinite. The contents of biogenic Si in plant and soil were governed by the reserve of weatherable primary minerals. The largest concentrations of biogenic Si in plant (6.9-7 g kg(-1)) and soil (50-58 g kg(-1)) occurred in the least weathered soils, where total Si content was above 225 g kg(-1). The lowest contents of biogenic Si in plant (2.8-4.3 g kg(-1)) and soil (8-31 g kg(-1)) occurred in the most weathered desilicated soils enriched with secondary oxides and clay minerals. Our data imply that soil weathering stage directly impacted the soil-to-plant transfer of silicon, and thereby the stock of biogenic Si in a soil-plant system involving a Si-accumulating plant. They further imply that soil type can influence the silicon soil-plant cycle and its hydrological output.

In banana plantations of the Caribbean, nitrogen (N) fertilization widely exceeds nutrient outputs after harvest. Under wet tropical climate, leaching results in considerable waste of N. Fertilization management aims at maintaining soil mineral N at the optimal level for banana nutrition throughout the year but it does not take into account variations in crop N demand or N supply through mineralization of crop residues. The dynamics of crop N demand and crop residue supply depend on the structure of banana populations, which become asynchronous with time. We designed the SIMBA-N model to simulate N dynamics in successive crop cycles of banana. The model calculates the N balance weekly, including N uptake by banana, N leaching, and N supply by organic matter mineralization. We validated the model using data from a field experiment comparing five levels of fertilization. Results showed SIMBA-N provides reliable indicators to support banana fertilization management taking into account N flows in the soil and change in N demand related to banana population structure.

Several plant species accumulate silicon, which is taken up by roots in soil solution. The Si concentration in soil solution can be governed by silicate dissolution and formation, and thus soil constitution. Here, we study the Si leaf content of mature banana plants (Musa acuminata cv Grande Naine) cropped on soils derived from andesitic ash in Guadeloupe through standard foliar analysis. The soils strongly differ in weathering stage and total Si content. The most desilicated soils (Andosol-Nitisol Ferralsol) occur in the wettest areas, on the Eastern slopes (Es) of the volcano exposed to rain bearing winds. Least weathered soils (Andosol-Cambisol) occur on Western slopes (Ws). The average leaf Si concentration ranges from 2.7 to 3.9 g kg(-1) for bananas cropped in Es soils, and from 7.7 to 9.6 g kg(-1) in Ws soils. The leaf Si concentrations are lowest for the Es gibbsite-rich Andosols and Ferralsols. The leaf Si concentration is positively correlated with soil CaCl2-extractable Si content, soil Si content and total reserve in weatherable minerals. The silicon content of banana leaves thus reveals the weathering stage of volcanic ash soils in Guadeloupe.

Correspondance: tixier@cirad.fr; International audience; Banana monocultures (Musa spp., AAA, Cavendish sub-group cv. Grande Naine) can have a detrimental impact on the environment. In these agro-systems, pesticide treatments can lead to surface and groundwater pollution, as is the case in the tropical insular conditions of the French West Indies. Using models to design alternative cropping systems is of growing interest but most of the research work has been concentrated on annual crops and most often in temperate climate. A specific model called SIMBA was built to assess environmental risks under a large range of cropping techniques and to help design more sustainable cropping systems. SIMBA simulates banana-cropping systems at field level over several cropping cycles. It includes sub-models that simulate soil structure, water balance, root nematode populations, yield, and economic outputs with a sound balance between representing the major phenomena well and keeping the model simple to reduce the parameterization costs in a large range of conditions. Agro-environmental indicators generated by the model make it possible to assess the major potential environmental impacts. The model has been developed and calibrated in Guadeloupe and Martinique and is used to draw up practical recommendations for farmers and for virtual experiments of agro-technological innovations or field management strategies. The structure of SIMBA is presented and a methodology is proposed for designing sustainable banana-based cropping systems using the model. SIMBA has been evaluated in a broad range of cropping systems in Guadeloupe by comparing model estimates to data collected in field experiments and surveys. Simulations lead to trends in rotation-based cropping systems characterized by systems that can be considered as intensive for profit evaluation, and combinations of frequent replanting, low nematicide application, no ploughing, and low fertilization level, for environmental evaluation. Simulations performed to optimize the replanting decision rule showed that relatively frequent replanting is good for profit while low frequency replantations (over four banana cycles) give a better environmental evaluation

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; International audience; Radopholus similis is a worldwide endoparasitic nematode that greatly hampers banana (Musa acuminata, Cavendish subgroup) productivity. Earthworms are known to closely interact with above-ground and under-ground soil biota and particularly with plants and microfaunal communities. This study was aimed at investigating, under greenhouse conditions, the effects of the earthworm Pontoscolex corethrurus on banana growth and nutrient uptake, and assessing the influences of this earthworm on the development of an inoculated population of R. similis. Six-week-old tissue culture banana plants were submitted to four treatments: with P. corethrurus, R. similis, P. corethrurus+R. similis, and a control with no earthworms or nematodes. At the end of the experiment, the P. corethrurus treatments showed significantly higher leaf surface areas, shoot dry root weights, and root fresh weights than those without earthworms. This root growth enhancement probably contributed to the evident but non-significant decrease in the density of nematodes in the roots, even though earthworms did not reduce the total number of nematodes per whole root system. Moreover, the presence of earthworms slightly alleviated the severity of root damage. N bioavailability in the soil, along with N, Ca, and Mg content of banana plants, were also significantly increased in the presence of earthworms. Our results demonstrated that banana plant growth and nutrition were positively influenced by earthworms. Cropping practices that boost the development of earthworm communities in soil should therefore be promoted to enhance sustainability and to naturally alleviate nematode impact.

E-mail Addresses: tixier@cirad.fr, dorel@cirad.fr, malezieux@cirad.fr; International audience; The harvest dynamic model (SIMBA-POP) was used to choose the best planting date of a banana field in order to optimise the gross income. The proposed method takes into account the seasonal variation of the selling price of bananas. The gross income was calculated weekly by multiplying the simulated number of bunches harvested weekly by the mean weight of bunches, and by the current selling price. The weekly gross income over the simulated period was then determined. The Study was carried out in Martinique (French West Indies) for climatic conditions corresponding to 50, 350, and 650 m in altitude and for different field management strategies (number of cropping cycles before replanting). The result of our simulations showed that the optimal planting month enables a 10-36% increase in income over the worst month

Like many intensive monocultures, some features of banana-based cropping systems may be detrimental to the environment. Pesticide use is a major cause of surface water and groundwater pollution. The risk of water pollution due to pesticides is very high in the insular areas of the French West Indies (FWI). In order to assess these risks and help design more sustainable cropping systems, we propose using an indicator to assess the risk of pesticide pollution over time (Rpest). Rpest provides dynamic assessments through a linkage with a cropping system model that simulates environmental factors and agricultural practices. An expert validation check was conducted and demonstrated that Rpest can rank cropping systems by risk as well as experts. A sensitivity analysis highlighted that the indicator can take the properties of active ingredients and pedoclimatic data into account in assessments. Rpest helps to pinpoint high pollution risk periods. It can also be used to test alternatives and compare systems. This tool can be integrated into a model-based, global, prototyping methodology used for more sustainable cropping systems.

Cover plant-based cropping systems have gained considerable attention over the last few years because of the recognized benefits of increasing the diversity of agrosystems to sustain services other than those pertaining to production. While agronomical tools and methods to assess these services in multispecies plant communities barely exist, trait-based approaches, originally developed in the field of comparative functional ecology, provide an appropriated framework to study the effects of plant diversity on agrosystems. The aim of this article is to discuss how a trait-based approach can be used to assess the services delivered in cover plant-based cropping system. We focus on semiperennial cropping systems based on cover plants, exemplified by the banana cropping systems. These systems are described in a first section to identify the services targeted. A second section, based on a literature survey, analyzes the processes associated with each service and identifies related effect traits of cover plants. A shortlist of markers to be used to assess agrosystem processes is proposed and hypothesis on trade-offs and synergies among services are formulated. In a third section, issues related to the scaling-up from plant traits to the services delivered by plant agricultural communities are discussed. Such an approach, originated in the field of ecology, appears highly promising to tackle agronomic issues and its application to agrosystems constitutes a challenging test of their genericity. It raises specific questions and stresses the need for new methodological developments, which could be part of a research agenda at the interface between the two disciplines.

We compare the effects of minimum and conventional tillage on banana growth, under irrigated and rain-fed conditions. Measurements of leaf growth, root length density and soil water depletion were made. We used a crop simulation model to understand and explain the differential behavior of banana plants in the experiments. Our approach consisted of (i) an adaptation of the STICS model, initially developed for temperate crops, to the banana crop grown under tropical conditions and (ii) use of the integrative ability of the model to identify the respective roles of irrigation and tillage. The adaptation of the model concerned the phasic development, and leaf and root growth. Some specific characteristics of the tropical environment were also introduced. The model points out that under irrigated conditions crop water requirements were always satisfied whatever the tillage depth. In that case, the difference in terms of leaf growth and yield between shallow and deep tillage treatments can be explained by the nitrogen deficit due to a poor root system. Rain-fed crops suffered from water shortage, but the increase in soil exploration, allowed by conventional tillage, compensated for the absence of irrigation. This work improves knowledge of the agro-physiology of the banana crop. It demonstrates the fundamental part played by the root system, which appears as an important limiting factor for a correct water and nutrient supply. It provides an opportunity to elaborate a global model for the banana crop. (Resume d'auteur)