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La Guadeloupe, comme de nombreux pays de la Caraïbe, montre une très forte dépendance aux importations alimentaires. Une des alternatives consisterait à mieux connaître la richesse de nos ressources agricoles pour mieux les domestiquer et les valoriser dans notre alimentation, notre culture et nos paysages. L’agrodiversité peut prendre des formes diverses – type, nombre, agencement d’espèces - en lien avec les influences culturelles des agriculteurs ou des jardiniers, leurs finalités, et les conditions pédoclimatiques des zones d’implantation. Il devient urgent d’inventorier cette agrodiversité et d’organiser la collecte, la conservation et l’accès à la diversité en semences locales. Réseau Semences Gwada propose une démarche originale pour dynamiser de façon durable, la filière des semences en Guadeloupe. Un premier état des lieux de l’agrodiversité cultivée et cultivable a été réalisé en mettant l’accent sur la perception de la diversité et sa conservation par les acteurs concernés. Un questionnaire web a été élaboré et soumis à l’interprofession agricole, aux agro-transformateurs, à la recherche agronomique, aux associations œuvrant au profit de l’agriculture paysanne ou de l’agriculture biologique, ou encore à des groupes de discussion locaux de jardins hébergés par les médias sociaux d’internet. Nos résultats ont démontré que la tradition, le goût, la rupture avec le mode de consommation conventionnel, et l’expertise sont liés avec la diversité cultivée dans les jardins. L’utilisation pratique des plantes est structurée en niches de motivations des cultivateurs (valeur agronomique, éligibilité et propriétés médicinales). Le partage d’expertises est en attente d’une structuration pour un engagement durable. Guadeloupe, like many Caribbean countries, is very dependent on food imports. One of the alternatives would be to gain a better understanding of the richness of our agricultural resources in order to better domesticate them and make use of them in our food, our culture and our landscapes. Agrodiversity can take various forms - type, number, arrangement of species - in relation to the cultural influences of farmers or gardeners, their purposes, and the soil and climate conditions of the areas where they are planted. It is becoming urgent to inventory this agrodiversity and to organise the collection, conservation and access to local seed diversity. Réseau Semences Gwada proposes an original approach to boost the seed sector in Guadeloupe in a sustainable manner. An initial inventory of cultivated and cultivable agrodiversity was carried out, focusing on the perception of diversity and its conservation by the stakeholders. A web questionnaire was developed and submitted to the agricultural interprofession, agro-processors, agronomic research, associations working for the benefit of peasant agriculture or organic farming, and local garden discussion groups hosted by the internet social media. Our results have shown that tradition, taste, break with conventional consumption patterns, and expertise are linked to the diversity grown in gardens. The practical use of plants is structured in niches of motivations of growers (agronomic value, eligibility and medicinal properties). The sharing of expertise is waiting for structuring and a sustainable commitment.

Landscape effects might impede or increase spore dispersal and disease risk for crops, as trees and hedges buffer winds and can behave as spore traps, therefore limiting diffusion of fungi, or, on the contrary, behave as disease relay once vegetation is infected and become inoculum sources. In this study, we investigated weekly prevalence of the pathogenic fungus Colletotrichum gloeosporioides on guava tree leaves, differentiating impacts of leaf height on tree, age, and location within leaf. We first estimated differences in prevalence for each covariate, and then related infection rates to weather effects during the year. Our results highlighted a great variance of prevalence among individual trees, and a lower contamination of tree tops, as well as a tendency for greater odds of infection in tips of young leaves compared to older ones. Last, we show evidence that individual tree contaminations are associated with different disease dynamics: early and dispersal-based, late and growth-based, as well as with intermediate dynamic ranges. Pathogen infection dynamics will thus be greatly impacted by cover characteristics at local scale, and tree cover should not be perceived as homogeneously driving disease levels.

International audience; Plantain (Musa paradisiaca AAB) is one of the main staple food crops in tropical areas, particularly in the Caribbean region. Therefore, supporting a sustainable production of plantain in this zone is crucial to secure food and to provide income to millions of people. We hypothesized that agroecological practices based on multifunctionality and biodiversity and that preserve soil should i) increase macrofauna abundance, ii) enhance soil chemical fertility, iii) improve soil physical structure, iv) reduce plant infestation by parasitic nematodes, and v) immediately achieve similar yield as in conventional systems. For this purpose, we compared plantain conventional and agroecological systems at the farm scale. The agroecological system consisted in a combination of three innovations: i) inputs of vermicompost to replace mineral fertilizers, ii) use of healthy planting material and iii) use of a mulching of living crop to control weeds. Ten months after the plantation, soil macrofauna abundance had doubled and taxonomic richness had increased by 45% in the agroecological system. In addition, soil structure was improved in the agroecological system (52% of biogenic aggregates in the agroecological system vs. 21 % in conventional systems), as well as the abundance of free-living nematodes associated to plantain roots increased by 73 % in the agroecological system. The abundance of Radopholus similis, one of main plant parasitic nematodes, decreased in the agroecological system. Moreover, the agroecological system achieved similar crop yield level than conventional systems. Agroecological practices are thus an efficient option to allow a fast transition from conventional to environmentally friendly cropping systems

Leaf-cutting ants (Hymenoptera: Formicidae) are one of the main pests found in the Americas and they cause global economic losses worth several billions of dollars. While pesticides have been the most widely used control method, new management alternatives in a context of agroecological transition are now being considered. This study focuses on the leaf-cutting ants species found in the pan-Amazon region. As part of efforts to improve management of these pests, this multi-criteria analysis of control strategies covers a total of 691 experiments collected from 153 studies, and the control were evaluated as a function of their management efficacy, environmental and human health impacts, and their ease of application. Chemical control methods were effective but posed a danger to human health and the environment, whereas mechanical methods and integrated management were more sustainable but not always very effective. Some of the biocontrol methods were evaluated as effective and safe for the environment and human health, including the use of entomopathogenic fungi Beauveria bassiana (Bals.-Criv) Vuill. (Hypocreales: Cordycipitaceae) and Metarhizium anisopliae (Metschn.) Sorokïn (Hypocreales: Clavicipitaceae) in the form of bait or sprayed in the nest, or the application of plant mulch in the nest using Tithonia diversifolia (Hemsley) A. Gray (Asterales: Asteraceae) or Canavalia ensiformis L. DC. (Fabales: Fabaceae). Because of variations in the efficacy data between laboratory and field tests, we are in favor of evaluating these control methods during field studies with different leaf-cutting ant species and under different environmental conditions. These methods should adopt experimental arrangements that are appropriate for local socioeconomic conditions adapted for farmers.

Remerciements à Daniel Imbert (Université des Antilles) et Lucienne Desfontaines (Inra Antilles-Guyane, UR ASTRO); International audience; In the Caribbean, Pterocarpus officinalis swamp forest, a coastal freshwater wetland, has been locally transformed by human activities into Colocasia esculenta monoculture (under the swamp forest) or pasture (where deforestation has occurred). The aim of this study was to evaluate the impact of three land uses of this tropical wetland (swamp forest, C. esculenta monoculture and pasture) on soil abiotic and biological features. We hypothesized that increasing the level of ecosystem alteration by agricultural intensification would negatively impact soil chemical characteristics, soil fauna diversity and carbon mineralization. As expected, land use significantly affected soil characteristics and changes followed the increasing intensity of land use. The ‘undisturbed system’, that is swamp forest, was characterized by a large soil organic matter content, a high level of soil moisture, a small phosphorus content and a slightly lower pH. These characteristics were correlated with a small faunal abundance and diversity and slow carbon (C) mineralization. The ‘low disturbance system’, that is C. esculenta monoculture, was the closest to swamp forest characteristics and changes between the both systems principally concerned a very slight decrease in organic matter content and very small increase in C mineralization and Coleoptera diversity. By contrast, all parameters (soil chemical characteristics, C mineralization and faunal abundance and diversity) were impacted in the most intensive land-use, pasture. Our study confirmed that agricultural practices have an influence on soil fauna and C mineralization processes in wetlands. Moreover, our study suggested that a C. esculenta traditional agroecosystem under swamp forest cover could be considered as an ‘eco-friendly’ agricultural practice.

online en avril 2016; International audience; In West and Central Africa and in the Caribbean, yam is one of the most important sources of carbohydrates and has a great potential to improve food security. The yam production sector is, however, now challenged by the satisfaction of evolving consumers' preferences. Since little is known about consumers' preferences regarding yams' characteristics, product quality, and the drivers of yam purchase, six focus group discussions were conducted (for a total of 31 participants). Among the purchasing criteria, price was considered more important than the others. It was followed by the external damage, the origin, and the size of the tuber. The most frequently cited consumption criteria were the taste, the texture, and color of flesh after cooking. Taste was considered more important than the other criteria. Three consumers' profiles were established reflecting heterogeneity in preferences, especially as concerns the willingness to pay for yam and consumption habits. They were designated as the Hedonistic, the Thrifty and the Flexible. Our results suggest that innovations can be implemented to sustain and stimulate the development of the yam sector in Guadeloupe. Two main development paths were identified. The first path is the valorization of the great existing diversity of yam varieties and the increase in the level of information for consumers about product attributes such as the cooking mode, the origin, and the mode of production. Building a marketing strategy based on the valorization of this diversity can help maintain and preserve yam's agro-biodiversity and the satisfaction of rapidly evolving consumption habits. The second path is the definition of yam ideotypes that suit consumers' needs. We expect that tailoring the production to consumers' needs will have a positive impact on global food security in the Caribbean region.

Managing the transition from conventional agriculture to agroecology needs to account for the diversity of farming systems. Here we evaluate whether indicators based on agrodiversity and implementation of agroecological practices can discriminate types of farms with different trajectories in the context of the agroecological transition. The indicators tested were coupled with production factor, performance and strategy variables to better target their need for innovation. We propose a composite indicator that captures the main agroecological practices implemented within the study area: the French Caribbean islands of Guadeloupe and Martinique. Data was collected from 215 farms selected on the basis of their production strategy and their diversity. Eight variables related to production factors (farm size, equipment number, total and family labor), performance (total gross margin per hectare), surface devoted to implementing agroecological practices (SAEP), diversity (number of species produced), and local context integration (proportion of affiliation to professional organizations) were used to perform correlation and multivariate analyses (PCA and cluster analysis). The two PCAs (one with and one without SAEP included in the analysis) grouped agroecological practices, diversity, family labor and gross margin per hectare variables and opposed them against production-factor variables (farm size, total labor, and equipment number). Five farm clusters were identified when including the agroecological practices indicator in the analysis, i.e., 1) small diversified family farms, 2) medium-sized diversified family farms, 3) medium-sized diversified entrepreneurial farms, 4) medium-sized specialized entrepreneurial farms, and 5) large specialized entrepreneurial farms, and these clusters showed different degrees of agroecological and diversity practice implementation. Two extreme strategies of agroecological improvement were identified between large farms with high levels of production factors mainly oriented toward a light transition based on perpetuating existing agricultural models, and small family farms with high levels of diversification that already implement agroecological practices. Limits of this new composite indicator are discussed, and avenues for improvement are proposed.

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; The burrowing nematode Radopholus similis and the lesion nematodes Pratylenchus spp. are considered as major constraints to banana cultivation worldwide. As an alternative to the use of chemical pesticides in commercial banana plantations, the possible role of the earthworm Pontoscolex corethrurus was studied regarding the reducing harmfulness of the main plant-feeding nematodes of banana. The interactions among banana plants, plant-feeding nematodes and earthworms have been tested in a controlled experiment combining treatments including or not earthworms and nematodes, over a complete vegetative banana development cycle. The aim of the work was to evaluate how earthworm activity can affect the pathogenicity of the three main plant-feeding nematodes associated with dessert banana (Musa spp. AAA group, cv. Cavendish) in Guadeloupe (French West Indies), R. similis, Pratylenchus coffeae and Helicotylenchus multicinctus. Results showed that damages caused by plant-feeding nematodes were lowered in the presence of the earthworm P. corethrurus; the population of plant-feeding nematodes did not decrease whereas root damage induced by nematodes was significantly reduced (50% reduction of root necrosis in the presence of earthworms). Moreover, in the presence of P. corethrurus, we observed a change of soil porosity. On the one hand, the burrowing activity of earthworms destroyed most of the initial structural porosity (mesobiotic pores, 3–300 _m) and on the other hand, they increased the volume of the finest structural pores diameter class (microbiotic pores, 0.3–3 _m). P. corethrurus also stimulated phosphorus mineralization. Soil bioturbation carried out by P. corethrurus could have enhanced the efficiency of microbial community that is involved in phosphorus bioavailability. This observation was corroborated by a higher phosphorus availability in earthworm casts (1386 ± 38 mg P kg−1 of dry matter in cast versus 778 ± 61 mg P kg−1 of dry matter in the soil compartment not influenced by earthworm activity), and a better plant phosphorus nutrition in the presence of earthworms. Phosphorus uptake resulted in a better plant nutrition and a better tolerance to plant-feeding nematodes. Besides, the reduction of the mesobiotic porosity by bioturbation could also have disturbed the nematodes activities during their soil phase and contributed to the reduction of their damage.

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; Agricultural policymakers are addressing the sustainable development issue by designing new agricultural systems. Farmers are ultimately asked to make deep changes at field scale. Designing cropping systems has previously been done using prototyping methodologies. Prototyping methodologies use a five-step designing process at field scale and request multicriteria analysis of the resulting prototypes. However, sustainable dynamics implies considering changes at larger scales, farm and region, as well as creating feedback and facilitating participation of all the stakeholders involved in the process. Here we studied citrus production in Guadeloupe, French West Indies, where farmers must reduce pesticide loads despite unresolved weed control issues. We designed the DISCS method, which stands for "participatory redesign and assess innovative cropping systems", to improve classical prototyping methods by implementing a multi-scale, multi-stakeholder, participatory approach. Compared to classical prototyping methods, the DISCS method differs by implementing three progress loops, at experimental field, farm, and regional scales. Three categories of professional stakeholders are involved: farmers, researchers, and agricultural advisers, who are collectively in charge of designing and testing cropping system prototypes. In addition, local public stakeholders including representatives of state institutions are consulted. Progress is assessed using scale-specific sets of indicators. The DISCS method was applied to develop low-pesticide citrus cropping systems. Five weed control prototypes were jointly designed by citrus farmers and researchers, and two multicriteria assessment tools were built for use at the experimental station and on the farms. Results show that involved farmers transferred the new techniques to their own farms on their own initiative, thus spontaneously becoming pilot farmers. The DISCS method is therefore the result of a co-design process between farmers and researchers. The DISCS method creates an ongoing dynamic relationship between agricultural and public stakeholders to build a solution that can continuously be adjusted to stakeholders' expectations.

Nowadays, tropical horticulture is often characterized with a high use of chemicals (pesticides and fertilizers) that may led to both a diffuse and long term pollution of soils and water resources and an acute contamination of fruits and vegetables with pesticide residues. In FWI, this is the case for banana, and to a lesser extent for vegetable and citrus, whose intensive production had local ecological impacts that went beyond social acceptability. Today, new UE and French regulations require the reduction of the use of chemicals to ensure safe production and environment protection, hence enhancing the need for new cropping systems less dependent upon chemicals. Among different alternatives, the design of new horticultural cropping systems based on the concept of ecological intensification that prioritizes ecological processes for the management of horticultural agroecosystems, is a very challenging one. Our approach is both global and integrative, using multicriteria assessment tools. It is focused at the field and farm scales. We propose here a conceptual framework based on the concept of ecological intensification that prioritizes the enhancement of biodiversity and organic status nutrients availability in cropping systems; and illustrate this framework through three case studies in FWI : i) pest control in tomato and banana cropping systems through enhanced plant and insect biodiversity, increased food web complexity and feedback regulations, ii) phosphorus availability in banana potting experiments through earthworms activity , and iii) weed control through cover crops in citrus orchards. Ecological intensification, although at a preliminary stage, is a promising strategy to design sustainable horticultural cropping systems, even in high phytosanitary pressure conditions. (Resume d'auteur)

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.

International audience; Ensuring the success of agriculture is at the heart of food security, and it is necessary to examine strategies that tackle agricultural development through the production and consumption of sustainable food products. One way to increase food security in small island states is to develop local food sectors by increasing consumers’ awareness about local products with sustainable characteristics. We designed an economic experiment to assess consumers’ willingness-to-pay (WTP) for yams with sustainable characteristics: the origin, the intrinsic quality of an alternative variety and the mode of production. The results showed that labelling significantly changes consumers’ valuation of the different yam profiles. Consumers’ WTP for local yams (2.85 € kg-1) was significantly higher than for imported yams (1.80 € kg-1), while the organic mode of production derives a significant premium if information on production methods has been disseminated. The results also suggested that organoleptic characteristics of new varieties should not be overlooked. We conclude on how the labelling strategy could be facilitated through a policy targeting the development of the local food sector.

Provisioning services, such as the production of food, feed, and fiber, have always been the main focus of agriculture. Since the 1950s, intensive cropping systems based on the cultivation of a single crop or a single cultivar, in simplified rotations or monocultures, and relying on extensive use of agrochemical inputs have been preferred to more diverse, self-sustaining cropping systems, regardless of the environmental consequences. However, there is increasing evidence that such intensive agroecosystems have led to a decline in biodiversity as well as threatening the environment and have damaged a number of ecosystem services such as the biogeochemical nutrient cycles and the regulation of climate and water quality. Consequently, the current challenge facing agriculture is to ensure the future of food production while reducing the use of inputs and limiting environmental impacts and the loss of biodiversity. Here, we review examples of multiple cropping systems that aim to use biotic interactions to reduce chemical inputs and provide more ecosystem services than just provisioning. Our main findings are the identification of underlying ecological processes and management strategies related to the provision of pairs of ecosystem services namely food production and a regulation service. We also found gaps between ecological knowledge and the constraints of agricultural practices in taking account of the interactions and possible trade-offs between multiple ecosystem services as well as socioeconomic constraints. We present guidelines for the design of multiple cropping systems combining ecological, agricultural, and genetic concepts and approaches.

International audience; The article studies the nutrient transfer mechanism and its control for mixed cropping systems. It presents a mathematical analysis and optimal control of the absorbed nutrient concentration, governed by a transport-diffusion equation in a bounded domain near the root system, satisfying to the Michaelis-Menten uptake law. The existence, uniqueness and positivity of a solution (the absorbed concentration) is proved. We also show that for a given plant we can determine the optimal amount of required nutrients for its growth. The characterization of the optimal control leading to the desired concentration at the root surface is obtained. Finally, some numerical simulations to evaluate the theoretical results are proposed.

Electrical impedance spectroscopy (EIS) is investigated as a non-destructive method for monitoring root growth of tomato. This paper aims to (i) review the basic principles of EIS applied to the characterisation of the different parts of the soil–root–stem-electrode continuum, (ii) experiment the validity of the relationship between root weight and root capacitance taking into account the influence of the soil and plant electrodes position, (iii) describe an EIS analysis of the root growth of tomato plants. All experiments were carried out in 50 dm3 containers either in hydroponics at 930 μS for the test of root fresh or dry weight and root capacitance relationships, or in a potting mix (oxisol) for electrode placement tests and EIS estimation of root growth. Electrical measurements of the soil–root–stem-electrode continuum were done with a two-electrode measuring system using unpolarisable Ag–AgCl electrodes. A ‘root cutting’ and a ‘progressively immersed root system’ experiments were carried out in order to validate the relationship between root capacitance and root mass at 1 kHz. The effects of soil electrode and plant electrode placement were also tested, pointing out the sensitivity of the method to the insertion height of the “plant electrode” into the stem. For the root growth experiment, Impedance Spectra (IS) measurements were made just before harvesting the roots for dry weight and length determination. Measurements were made 14, 22, 26 and 39 days after planting, until flowering. The IS of the soil–root–stem-electrode continuum was modelled by a lumped electric circuit consisting of a series resistor R 0 for the soil and of four parallel resistance (R i )-capacitance (C i ) circuits for the other components of the circuit. The model had nine parameters whose values were estimated by Complex Nonlinear Least Squares curve fitting. A stepwise ascendant regression was used to identify the electrical parameters that better correlated with root dry mass or length increment: C 3 and C 4 were well correlated with root dry mass with a r 2 of 0.975, whereas root length was explained by the combination of 1/R 3, C 3, 1/R 2 and 1/R 1 with a r 2 of 0.986. This work may be considered as a new methodological contribution to the understanding of root electrical properties in the non-destructive diagnosis of root systems.

Soil constraints linked to low pH reduce grain yield in about 10% of the maize growing area in tropical developing countries. The aim of this research was to elucidate the reasons for this maize yield reduction on an oxisol of Guadeloupe. The field experiment had two treatments: the native non-limed soil (NLI, pH 4.5, 2.1 cmol Al kg−1, corresponding to 20% Al saturation), and the same soil limed 6 years prior to the experiment (LI, pH 5.3, 0 cmol Al kg−1). The soils were fertilized with P and N. The above-ground biomass, root biomass at flowering, grain yield and yield components, leaf area index (LAI), light interception, radiation-use-efficiency (RUE), P and N uptake, soil water storage, and soil mineral N were measured during the maize cycle. The allometric relationships between shoot N concentration, LAI and above-ground biomass in LI were similar to those reported for maize cropped in temperate regions, indicating that these relationships are also useful to describe maize growth on tropical soils without Al toxicity. In NLI, soil acidity severely affected leaf appearance, leaf size and consequently the LAI, which was reduced by 60% at flowering, although the RUE was not affected. Therefore, the reduction in the above-ground biomass (30% at flowering) and grain yield (47%) were due to the lower LAI and light interception. At flowering, the root/shoot ratio was 0.25 in NLI and 0.17 in LI, and the root biomass in NLI was reduced by 64% compared to LI. Nitrogen uptake was also reduced in NLI in spite of high soil N availability. Nevertheless, shoot N concentration vs aboveground biomass showed a typical decline in both treatments. In NLI, the shoot P concentration vs above-ground biomass relationship showed an increase in the early stages, indicating that P uptake and root-shoot competition for the absorbed P in the early plant stages controlled the establishment and the development of the leaf area.

Since the 1950s, intensive and specialized agricultural systems using a few select species and relying heavily on agrochemical inputs have enabled a huge increase in food production. However, in parallel, drawbacks appeared including biodiversity loss, greenhouse gas emission, erosion, and water pollution. Today shifting farming systems to mitigate soil degradation trends is indispensable. Using viability theory, we propose a dynamic model of the sequence of agricultural productions and practices that can be implemented in the long term to restore soil quality while respecting a set of agronomic and economic constraints. The paths to soil restoration vary depending on agronomic and economic constraints, the time available for restoration, the initial soil conditions, and investment capacities. Economic valuation of the minimum cost of restoration shows that the agroecological transition may be costly and that farmers can have difficulty meeting the costs, thus raising the question of how the cost of agroecological transition is to be shared. Recommendations for Resource Managers The mathematical viability theory is used to design a new model of farm management to assess possibilities and cost of the agroecological transition more precisely the successive choices of crops and agricultural practices intended to restore topsoil quality. This discrete dynamical model has an irregular time step corresponding to agricultural cycles and to dates of parcel release retrieved by using an inverse approach. The agronomic and economic constraints are mixed depending both on states and controls. The economic constraints are imposed on a monthly time step while states and controls variables evolve with the agricultural cycles what best fit the economic situation farmers must face. The trajectory selection criteria is the minimum cost of restoration. Optimal viable strategies depend on initial soil quality and available capital, time of exercise, constraints, and of crops and practices diversification. Computations were made with a software specially developed for this study using data sets collected in the French West Indies.

International audience; New cropping alternatives are explored in response to the drawbacks of the Green Revolution. Alternative practices use the ecological regulations of agroecosystems, and strengthen and manage agricultural biodiversity. Multi-species cropping systems are good models to seek innovative solutions. Indeed the combination of crops, ranging from simplest forms to complex multi-stage associations, such as agroforests, have allowed many populations to maintain their production conditions, while at the same time overcoming severe shocks such as droughts, epidemics or changes in market prices. An empirical agroecology has thus been created mainly using traditional knowledge. We present the following benefits provided by the ecosystem services of mixed cropping: (1) yields are often higher than in monocultures, (2) the amount of mineral and organic fertilizers is decreased two times, (3) mixed cropping is an effective alternative to pesticides, (4) water and energy is saved, (5) soil quality is preserved, and (6) worktime is better managed. A true agroecological engineering approach, linking scientific and empirical knowledge can thus be designed.

International audience; Feeding a growing population and ensuring food security whilst protecting ecosystems and natural resources are crucial priorities in times of global changes. Agroecology promotes innovative drivers of change for a smart agriculture that meets the specifications of ecological transition. Managing soil interactions offer largely unexplored potential to increase agricultural yields and reduce pressures on the environment. Crop losses of 10 % are due to soil-borne pests causing root rot, root blackening, wilt, stunting or seedling damping-off. One promising approach is to encourage pest regulation provided by soil interactions to decrease the inputs of pesticides. However, limited success of this approach in field applications raises questions as to how this might be best accomplished. Here we review advances in plant protection against soil-borne pests and implications for disease-suppressive agrosystems design. Root infection processes are increasingly understood. Plants protect themselves by naturally engineering the composition of their rhizosphere. They fight soil pests both by root production of toxic chemicals and by favoring pest enemies. The analysis of the chemical dialogue offers new perspectives to enhance biocontrol effectiveness of disease-suppressive soils and antagonists. High throughput technologies provide unprecedented knowledge on rhizosphere interactions and implications for crop health. Agroecological engineering approaches overcome the limitations of conventional protection strategies by promoting multi-functional practices harnessing rhizosphere bioprotection. Breeding crop cultivars which capitalize on plant-microbiome interactions or associating plants and biocontrol agents early in their life offers innovative ways to contribute to disease-suppressive agroecosystems design. Integrating interacting species with strong ability to recruit beneficial microorganisms or secrete toxic compounds in mixed cropping systems is a key issue. Based on functional biodiversity management, these systems will provide underpinning ecosystem services and enhance global resiliency of agroecosystems.

Industrial agriculture has clearly reached its limits. Industrial agriculture is not able anymore to satisfy the basic needs of the growing worldwide population while ensuring the conditions of reproduction of natural assets. New production models have to be designed to protect and reclame polluted and degraded agricultural areas. Agroecology is considered as a promising way to achieve ecologically-intensive agrosystems, since the seminal contribution of Altieri in 1995. Nevertheless agroecology has not fully emerged as a scientific discipline yet. Agroecology is more that a traditional scientific discipline because agroecology breaks the frontiers between biophysical sciences and social sciences. This chapter reviews the roots and evolution of agroecology in the first section. Here we propose a mathematical theory of viability to handle uncertainty and complexity within agrosystems. This theory allows to define a kern of viability in which the agrosystem stay viable in the long term (section “Scientific stakes: New frontiers”). However, agroecological innovations create new uncertainties and controversies that must be solved. Some solutions can be found individually while other solutions must by co-constructed using innovative collective actions and hydrid forums (Callon et al. 2001, section “Scientific controversy and uncertainty”). Such collective knowledge makes agroecology as the starting point of a representative democracy by setting up adaptive governance on territories (section “How to manage agrosystems in the context of global changes?”).

International audience; The climate change crisis is inducing severe energy and food shortages in tropical regions. A potential solution is to build agroecological systems as an alternative to intensive and industrial agriculture. For that research should focus on the functions of animal and livestock farming systems. Positive and negative function effects should be assessed. This is particularly important in developing countries where most of tomorrow’s food and feed will have to be produced. What are the main issues for animal production in the tropics? The major challenges are how to redesign productivity and food security, economic efficiency and environmental preservation, and how to integrate economy and environment. A multidisciplinary approach is necessary to address such complex problems, where interactions among interdependent components of the system result in multicausality. The concept of livestock farming system, with its double consistency of social and biophysical dimensions, can help address complex problems. The concepts of livestock farming system and of agroecology can be easily combined to design sustainable animal production systems. Enhancing agroecological approaches that lead to both food security and biodiversity conservation must involve spreading concepts through practices, particularly to solve the problems of small farmers. As so, the purpose of the paper is to highlight many case studies. The animal and farming system ecoservices are described at the animal level with the case of the multifunctional tropical goat and also at the territory level with the case of agrosylvopastoralism focusing the role played by the animal. Finally, the socio-cultural functions of animals or systems in this region are described. The double dimension of livestock system concept allows the integration of the livestock keepers in the human and societal context to attain agroecological objectives which is recognised as a core objective to attain according through the agroecological perspective. Topical livestock farming systems can show their potential to reach sustainability and help family economy.

Field root investigations are often limited by the static nature of classical observations, resulting in the need to develop alternative methodologies that allow dynamic interpretation of root architecture variability on the basis of static measurements. The objectives of this work were (i) to evaluate the use of selected morphological indicators, namely root apical diameter (Da) and the length of the apical unbranched zone (LAUZ), in predicting primary and lateral root growth patterns in banana trees, (ii) to propose a field methodology for the assessment of root dynamics based on static measurements. Banana trees (Musa acuminata cv `Grande Naine') were grown in 5 rhizotrons as well as in field conditions, respectively on pouzzolane and Mollic Andosols. In rhizotrons, root growth analysis was carried out by reporting root elongation, Da and LAUZ, three times a week. In field conditions, 4 series of excavations were made at three-week intervals. Apart from root growth rate, measurements were the same as those in the rhizotrons.

This study investigated the patterns of root growth and water uptake of maize (Zea mays L.) and cowpea (Vigna unguiculata (L.) Walp) grown in a mixture under greenhouse conditions. The plants were grown in root boxes for 5 weeks under 2 watering regimes; fully irrigated and water stress conditions, followed by a 5-day drying cycle imposed during the 6th week of growth. Water uptake patterns were analysed during the drying cycle. The two-dimensional distribution of the roots of both plants in the boxes was determined immediately at the end of the drying cycle. Under well-irrigated conditions, the roots of the component plants grew profusely into all sections of the root box and intermingled considerably. Water stress resulted in the decline of root growth of maize and cowpea but the root:shoot ratios of maize and cowpea were not affected, suggesting that there was no significant effect of water stress on root:shoot partitioning. However, water stress affected the biomass distribution between fine and coarse roots in cowpea. About 64% by weight of cowpea roots under water stress were coarse whereas as against 48% under well-irrigated conditions. Furthermore, water stress generally restricted the lateral extent of the roots of both maize and cowpea with a tendency of clumping together of the root systems and a reduced degree of intermingling. Thus, the extent of mixing of the root systems was apparently controlled by the availability of soil water. Water uptake from the well-irrigated soil in the root boxes was initially restricted to the sections directly below the base of each plant. Although roots of both plants were present in almost all sections of the root box, all the sections did not contribute simultaneously to water uptake by each plant. Water uptake was delayed from the middle intermingled zones. In effect, uptake patterns did not relate generally to the root distribution. The tendency was for the component plants to initially `avoid' water uptake from zones of intense intermingling or competition.

A knowledge of above and below ground plant interactions for water is essential to understand the performance of intercropped systems. In this work, root water potential dynamics and water uptake partitioning were compared between single crops and intercrops, using a simulation model. Four root maps having 498, 364, 431 and 431 soil-root contacts were used. In the first and second cases, single crops with ‘deep’ and ‘surface’ roots were considered, whereas in the third and fourth cases, roots of two mixed crops were simultaneously considered with different row spacing (40 cm and 60 cm). Two soils corresponding to a clay and a silty clay loam were used in the calculations. A total maximum evapotranspiration of 6 mm d-1 for both single or mixed crops was considered, for the mixed crops however, two transpiration distributions between the crops were analyzed (3:3 mm d-1, or 4:2 mm d-1 for each crop, respectively). The model was based on a previous theoretical framework applied to single or intercropped plants having spatially distributed roots in a two-dimensional domain. Although water stress occurred more rapidly in the loam than in the clay, due to the rapid decrease of the soil water reserve in the loam, the role of the root arrangement appeared to be crucial for water availability. Interactions between the distribution of transpiration among mixed crops and the architecture of the root systems which were in competition led to water movements from zones with one plant to another, or vice versa, which corresponded to specific competition or facilitation effects. Decreasing the distances between roots may increase competition for water, although it may determine greater water potential gradients in the soil that increase lateral or vertical water fluxes in the soil profile. The effects of the root competition on water uptake were quite complicated, depending on both environmental conditions, soil hydrodynamic properties, and time scales. Although some biological adaptive mechanisms were disregarded in the analysis, the physically 2-D based model may be considered as a tool to study the exploitation of environmental heterogeneity at microsite scales.

Based on fractal and pipe model assumptions, a static three-dimensional model of the Gliricidia sepium root system was developed, in order to provide a basis for the prediction of root branching, size and mass in an alley cropping system. The model was built from observations about the topology, branching rules, link length and diameter, and root orientation, provided by in situ and extracted root systems. Evaluation tests were carried out at the plant level and at the field level. These tests principally concerned coefficients α and q –- the proportionality factor α between total cross-sectional area of a root before and after branching, and allocation parameter q that defines the partitioning of biomass between the new links after a branching event –- that could be considered as key variables of this fractal approach. Although independent of root diameter, these coefficients showed a certain variability that may affect the precision of the predictions. When calibrated, however, the model provided suitable predictions of root dry matter, total root length and root diameter at the plant level. At the field level, the simulation of 2D root maps was accurate for root distribution patterns, but the number of simulated root dots was underestimated in the surface layers. Hence recommendations were made to improve the model with regard to α and q. This static approach appeared to be well suited to study the root system of adult trees. Compared with explicit models, the main advantage of the fractal approach is its plasticity and ease of use.

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)

A knowledge of plant interactions above and below ground with respect to water is essential to understand the performance of intercrop systems. In this study, a physically based framework is proposed to analyse the competition for soil water in the case of intercropped plants. A radiative transfer model, associated with a transpiration-partitioning model based on a modified form of the Penman-Monteith equation, was used to estimate the evaporative demand of maize (Zea mays L.) and sorghum ( Sorghum vulgare R.) intercrops. In order to model soil–root water transport, the root water potential of each species was calculated so as to minimise the difference between the evaporative demand and the amount of water taken up by each species. A characterisation of the micrometeorological conditions (net radiation, photosynthetically active radiation, air temperature and humidity, rain), plant water relations (leaf area index, leaf water potential, stomatal conductance, sap flow measurements), as well as the two-component root systems and water balance (soil–root impacts, soil evaporation) was carried out during a 7-day experiment with densities of about 4.2 plant m-2 for both maize and sorghum. Comparison of the measured and calculated transpiration values shows that the slopes of the measured versus predicted regression lines for hourly transpiration were 0.823 and 0.778 for maize and sorghum, respectively. Overall trends in the variation of volumetric water content profiles are also reasonably well described. This model could be useful for analysing competition where several root systems are present under various environmental conditions.

Nowadays, consumers are more and more concerned about the traceability of the food they purchase. As a response to this phenomenon, labels have flourished highlighting the environmental impact of products for some, their nutritive characteristics or their origin for others. In this context, we wonder about how food production sectors can meet the consumers’ demand and about the role of labeling as a tool to foster the sustainable development of food sectors. We base our analysis on the case of the yam sector in Guadeloupe. Food sectors in the tropics face heavy constraints (Scott, Rosegrant et al. 2000; Charlery de la Masselière 2002). Yam is the first food crop in Guadeloupe both in area (450 ha) and production (6 300 t). It covers 78% of the needs of the territory (Agreste 2009; Chambre Agriculture 2010). Nevertheless, the decrease by half of its cultivated area during the last decade reveals that it is on the decline (Agreste 2009). During this period of time, the production and consumption of yam has been highly impacted by the discovery of a long-lasting pollution of soils by chlordecone, a pesticide that was previously used in banana fields. Today, by decree, farmers who want to grow yam in the contaminated perimeter have to get their production analyzed before selling it on the marketplace. Guadeloupian consumers are quite suspicious regarding the presence of pesticides in local food but still yam is still part of the diet of the population (Merlo, 2007). Given the above we wondered about consumers’ perception of local yam if they could be reassured regarding the absence of pesticides in yam tubers. We also investigate the interest and implication of certification for yam farmers. Our work aims to shed light on how farmers and consumers can interact to design a sustainable food production sector. We look at both the supply and demand side and discuss about the ways to connect both views in a labeling scheme. According to the existing literature about farmers’ decision making (Cerf and Sébillotte 1988; Duru, Papy et al. 1988; Sébillotte and Soler 1988; Bonneval 1993; Marshall, Bonneviale et al. 1994), we studied farmers’ productive and commercial strategies regarding yam and accordingly built a typology of the different farming systems that exist in Guadeloupe. We then looked for each type at the costs and returns of growing yam – using the economic results simulation tool of yam crop: Ignamarge© - and examined the economic implications of certification. Our analysis revealed the existence of six types of yam producing farms for commercial purposes. For some types, yam appears to be the most important crop and is mostly sold in direct sale therefore procuring the highest returns to the farmers. For some others, it is only part a diversification crop among others and is traded via a farmers’ cooperative or thanks to intermediaries. In those last schemes, the value is shared among the different actors along the food chain. Getting certified could match with some of the strategies developed by farmers but would imply them to change some of their production and commercial practices. Additionally certification would require the yam sector to increase its organizational capacity since farmers’ strategies are rather individual at present. On the other hand we set up a laboratory experiment to investigate whether consumers were willing to pay a premium for two different types of labels since Levitt and List (2007) showed that laboratory behavior is a good indicator of behavior in the field. We based our experiment on the protocol developed by Lange et al. (2002) and adopted by Bougherara and Combris (2009). The experimental method makes it feasible to estimate consumers’ valuation of specific characteristics by controlling precisely the information on products. Therefore it is possible to compare consumers’ willingness-to-pay for a little variation in characteristics of otherwise identical products. This comparison allows appraising the substitution relation among two characteristics. To achieve this goal, we used the BDM procedure (Beker, De Groot, Marshak, 1964) to elicit the willingness-to-pay for locally produced yams (outside of the contaminated perimeter) and organically grown yams. Consumers were recruited according to a set of criteria such as their yam consumption habits, getting involved in food purchasing at home and not being regular participants of marketing studies. Then we estimated tobit models of the participants’ willingness to pay, one for each profile. Results showed a significant change of the participants’ WTP when yams were labeled (figure 1) and that they were ready to pay a premium for locally produced yam and organically grown yam. Considering the above we discuss the consequences of labeling for farmers and consumers and how the strategies of those different actors can coincide. Our work raises the question of the type of policy instruments that need to be implemented to ensure that certification schemes help food sectors to guaranty quality and achieve sustainability.

International audience; Leaf-cutting ants (Formicidae, Myrmicinae, Attini) are found on the American continent and in the Caribbean and are known to live in symbiosis with a fungus. Among Attini tribe, Atta and Acromyrmex are the two genera, which commonly depend on fresh plant leaves and other plant material for their fungal garden. Overall, these ants are among the most economically damaging herbivorous species. A. octospinosus is classified among the most serious pests of tropical and subtropical America. Due to its foraging activity, it can cause serious damages from 20 to 30 % of crop production. Huge losses were observed in several vegetable and fruit crops, in crop of cacao or citrus orchards and in protected areas where some species may completely disappear due to their endemism. Economic losses due to these ants were estimated at several million dollars per year. Although Acromyrmex octospinosus is one of the most important species of leaf-cutters because of its economic impact there is a lack of review in the literature. We review here the distribution, biology and different kind of control used and sustainable methods that can possibly help to manage. A. octospinosus is found only in Neotropics from Central America to northern of South America, including parts of West Indies. A colony is divided into males, breeding females, or gyne, and three castes of workers: small workers or ‘minor’, medium worker or ‘media’ and large workers or ‘major’. Pheromones are indispensable supports of social life of A. octospinosus. Foraging is conditioned by trail pheromone and takes place along a ‘line’ involving all castes of the colony. The foraging is divided in several steps. Indeed, the ants cut the plant material, transport it into the nest, lick it, cut it into smaller pieces, chew it, depose fecal fluid on it, cultivate mycelium fragment on this prepared mixture and incorporate it into the symbiotic fungus. Symbiotic fungus, or ‘fungus garden’, is a Basidomycete, Leucocoprinus gongylophorus (Heim) Moeller. It is the exclusive nutrition of both juvenile stages and the queen and is also a supplement of the adult workers diet. The ant also lives with an actinomycete, Pseudonocardia sp. This symbiont grows on the cuticle of all ants of the colony and protects fungus garden against fungal competitors and ants against ubiquist entomopathogenic bacteria and fungi. The first techniques used to fight against A. octospinosus were mechanical methods which have only local efficiency and do not prevent from the reestablishment of colonies. Synthetic chemical control against A. octospinosus began in the twentieth century with a direct chemical control and afterward with toxic baits. The efficiency of these controls was limited but all of them caused severe injuries on environment and human health. This situation has prompted an increasing interest in alternative methods to control this pest. Laboratory and field tests of biological control were performed with spores of pathogenous fungus or ants predators into nest, with fungal symbiont’s extract and trail pheromone, with entomopathogenic fungus and nematodes. Most of these methods did not give the desired effect or were not confirmed in situ. Biopesticides using insecticidal and fungicidal plants are known to be environmentally safe because of their non-phytotoxicity, biodegradability and renewability. Thus, another alternative to chemical control of A. octospinosus has been explored with the insecticidal or fungicidal activities of plants extracts, which showed various effects on both A. octospinosus workers and Leucocoprinus gongylophorus in vitro cultures. These tests showed very encouraging in vitro preliminary results and may serve as alternatives to synthetic compounds to develop safer control agents of leaf-cutting ants. Complex relationships and tripartite mutualism are involved between ants, fungus and actinomycete. All studies investigated only one side management. A tripartite management based on a combination of the three strategies should promote a more efficient integrated control and provide some interesting options for the control of this pest.

National audience

Leaf-cutting ants, Acromyrmex octospinosus (Reich), are considering among the most important pest species of the New World. Until now, the main insecticides used for controlling these ants were synthetic chemicals. Leaf-cutting ants live in obligate symbiosis with abasidiomycete fungus, Leucocoprinus gongylophorus (Heim) Moeller. The crucial role of this symbiotic partner in the nest of leaf-cutting ants has prompted us to focus on A. octospinosus management through the use of fungicides in our study. Five parts of plants identified for their antifungal potential through TRAMIL ethnopharmacological surveys were tested: 1) bulbs of Allium cepa L.; 2) seed pods of Allium sativum L.; 3) green fruits of Lycopersicon esculentum L.; 4) leaves of Manihot esculenta Crantz; and 5) leaves of Senna alata (L.) Roxburgh. One plant extract with strong fungicidal activity (S. alata) against L. gongylophorus was found. The other extracts had lesser fungistatic or fungicidal effects depending on the concentrations used. The data presented in this study showed that TRAMILs fungicidal plant extracts have potential to control the symbiotic fungus of leaf cutting ants, in particular a foliage extract of S. alata.

International audience; Leaf-cutting ants of the Attini tribe are a major pest of agricultural and forestry productions in the New World. Economic losses caused by these ants were estimated at several million dollars per year. These ants need to live in symbiosis with a basidiomycete fungus. Due to their mutualistic interaction with the symbiotic fungus, management of Attini ants can be done with insecticides or fungicides or both. So far, synthetic pesticides were the main control means, albeit with negative effects on the environment. Very few studies describe alternative methods for the control of leaf-cutting ants such as the use of insecticidal and fungicidal plant extracts. There is therefore a need of knowledge on phytochemicals and plants that could be used as insecticides and fungicides. Here, we review chemicals of plant origin and species with insecticidal and fungicidal activities. We establish a list of plants and phytochemicals that could manage leaf-cutting ants and also other insects, notably insects that use fungus-based agriculture. An exhaustive literature search of 1965 references from 1923 to 2010 was conducted using scientific databases, chemical databases, botanical databases, and books to identify published papers related to insecticidal and fungicidal chemical compounds stemmed from plant species. The major points are the following: (1) 119 and 284 chemicals have been cited in the literature for their insecticidal and fungicidal activities, respectively; (2) 656 and 1,064 plant species have significant insecticidal and fungicidal activities, respectively; (3) 3 main chemical classes were most cited for these activities: alkaloids, phenolics, and terpenoids; (4) 20 interesting chemicals with the both insecticidal and fungicidal activities were found; and (5) 305 plant species containing these chemicals were cited. To conclude, 20 chemicals: caryophyllene oxide, cinnamaldehyde, eugenol, helenalin, linalool, menthone, myristicin, pulegone, thymol, anethole, anisaldehyde, elemicin, isopimpinellin, plumbagin, podophyllotoxin, psoralen, xanthotoxin, anonaine, solamargine, and tomatine; two main plant families, Lamiaceae and Apiaceae; and 17 species of these families were particularly interesting for the management of leaf-cutting ants.

Banana (Musa sp.) residues contain two thirds of the plant nitrogen (N) content at harvest which may represent a large N source for the daughter plant and contribute to reducing fertilizer rates. Our aim was to assess the decomposition kinetics of above- and below-ground banana residues, and to determine the uptake of the released N by the daughter plant. Residue decomposition was analyzed under laboratory and field conditions, and plant N uptake was evaluated in the field using 15N-labelled above-ground residues. The decomposition kinetics was interpreted with a simulation model. In the laboratory, residue decomposition showed an immobilization phase followed by remineralization. The immobilization phase was longer and remineralization was smaller for roots due to their higher C:N ratio and lignin content. The model satisfactorily described both phases and the effect of the residue C:N ratio. Experimental and model results indicated that root residues would be a minor N source for the daughter plant. In the field, above-ground residues decomposed according to first order kinetics. Residue half-life was 2 d in the laboratory and 32 d in the field, which was due to poorer soil–residue contact in the field. At the time of harvest of the daughter plant, 39% of residue N was recovered in the plant, 54% in the topsoil, and 3% in the remaining residues. About 4% of residue N was probably lost by leaching. Nitrogen derived from residues represented 19% (14 kg N ha−1) of N in bunches of the daughter plant and 18% (39 kg ha−1) of the whole plant N. Our study showed that above-ground residue N was an effective N source for the daughter plant, with a good overlap between the period of N release and that of greatest plant demand which reduced the risk of N leaching.

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; To reduce chemical inputs while maintaining crop yield, disturbed ecosystem functions must be restored, for example by cover-crops. In these cropping systems, because of competition between species, soil resources must be carefully managed. Dedicated tools and models are needed that account for the adverse effects of the cover-crop on the cash crop in terms of resource availability. Besides classical agronomic calculations of stress indices, which are difficult to generalize and require numerous parameters, recent work in ecology has related plant traits, like the biomass accumulated, to the resource availability during the whole plant cycle. Following such a simple approach, the objectives of this study were (i) to determine the effects of water and nitrogen limitations on banana growth and development and to test whether simple integrated traits can highlight the effects of these stresses on banana growth, (ii) to parameterize a simple generic module of soil water and nitrogen availability linked to SIMBA GROW, the growth module of the banana crop model SIMBA, (iii) to assess the ability of the model to simulate banana growth and development in the environmental conditions of a banana/cover-crop system, with particular attention on the effects of changes in plot temperature on model outputs. Three experiments were conducted on whole production cycles to investigate the effects of different water regimes, different nitrogen fertilization levels, and the cover-crop Neonotonia wightii on banana growth, nutritional status, and date of flowering. Results showed low nitrogen availability affected banana growth only weakly but decreased leaf nitrogen content and delayed flowering. Low water availability delayed flowering and decreased banana growth. In both cases, the delayed flowering allowed longer banana growth, which balanced the negative effect of low availability on the growth rate. The cover-crop modified both the rooting depth of the banana, and thus the amount of resources accessible to the banana roots, and the plot microclimate, especially air temperature. The model correctly reproduced the differences of date of flowering and leaf area index at flowering for a first cycle of production between a bare-soil and a cover-crop system, provided air temperature was reduced by 2-3% due to the cover-crop. To conclude, this study showed that in fairly constant environmental conditions (temperature, radiation and rainfall) a simplified model using resource availability over the growing period and integrated plant traits satisfactorily simulates banana growth in an intercropped system.

International audience; This chapter reviews studies dealing with the characterization of the plant root system by the electrical impedance method, i.e., with resistance and capacitance at a single frequency or at multifrequencies, according to the approach used in electrical impedance spectroscopy (EIS). Several studies have shown a correlation between electrical capacitance and resistance at a single low frequency with root biomass and morphology (e.g., surface area). It has not been possible to define clearly which part of the root system the electrical parameters represent. The circuitry in the stem–root–soil continuum has been analyzed in more detail by means of EIS. Using this approach, lumped and distributed models have been formulated that consider the role of roots in the context of other components in the circuitry. By means of EIS, a parameter referring to root capacitance was found to correlate positively with root biomass and root surface area. Several open questions remain with regard to the applications of the method. More studies are needed for the evaluation of longitudinal and radial electric field distribution between root interior and soil along the root system from root collar to root tips. In addition, further studies are needed under standardized measurement conditions with soils of different ionic composition and texture as the growing substrate, and also by taking into account the role played by mycorrhizas.

XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Citrus, Bananas and other Tropical Fruits under Subtropical Conditions; International audience; Weed management is an important point of citrus production in Guadeloupe (French West Indies). Orchards are traditionally planted on sloping ground, and the use of herbicides regularly sprayed on the whole farm is the most common practice. Such a practice impacts the environment and the production benefits. Introduction of cover crops on these orchards is an interesting alternative. The very first aim of cover crops is to control weeds, but benefits in terms of erosion and other services are also expected. This study consists in quantifying the effects of cover crop introduction on mandarin orchards (Citrus reticulate ‘Frémont’). The cover crop system is designed in order to obtain a perennial association and to limit chemical intervention as much as possible. Over the 3 years course of the study, two different modalities were compared: (i) farmer practice, mandarin orchard with herbicide (Glyphosate) every 2 months, and (ii) mandarin orchard in association with Neonotonia wightii. Despite some difficulties in setting up the system, N. wightii efficiently suppressed weeds after 6 months. No more herbicide was sprayed on the associated plot while the bare ground plot received 5 herbicides a year. Meanwhile, no significant difference in the predawn water potential of the soil has been revealed between N. wightii and bare ground conditions. This indicates that N. wightii use growth does not entail additional water supply. After 3 years of experimentation, no impact on the orchard performance of the field has been observed. Experimentation is still on-going to estimate the transfer of this new technique to the farmer.; Dans cette publication nous analysons les effets de l'introduction d'une plante de couverture (Neonotonia wightii) pour maîtriser l'enherbement des vergers d'agrumes. L'expérimentation a été menée chez un producteur (verger de mandarinier adulte) sur des sols non mécanisables (forte pente et empierrement). Nous avons comparé la pratique de ce producteur, principalement basée sur la maîtrise des adventices par des herbicides à celle, innovante, où N. wightii permettrait d'assurer cette maîtrise des adventices. Les effets induits de l'introduction de cette plante de service, et notamment ceux liés aux compétitions pour l'eau et les éléments fertilisants entre cette plantes et la culture de rente, ont été mesurés. Après 3 ans d'expérimentation il s'avère, que dans ce cas d'étude (verger adulte), N. wightii a permis d'assurer la maîtrise des adventices sans recours à des herbicides chimiques ; et ce sans qu'aucun impact négatif sur la culture de rente n'ait été mesuré.

UMR 1334 AGAP : Equipe AFEF ‘Architecture et Fonctionnement des Espèces fruitières’ ; Team AFFS ‘Architecture and Functioning of Fruit Species’ Contact: francois.bussiere@antilles.inra.fr; National audience; Sustainable agricultural production in the humid tropics leads to several challenges as limitation of soil and climate constraints, mitigation of diseases and pests impacts, improving sustainable access to resources avoiding potentially polluting and expensive inputs. From the beginning of the eighties’ INRA initiated researches programmes and proposed several specific answers to new challenges of tropical crops and environments. As simple technological transfers showed their limits in tropical conditions, specific knowledge was developed on soil liming, irrigation and organic matter management, plant nutrition and protection by mulches, intercropping as well as plant breeding and biological control. Several innovations designed for Guadeloupe and Martinique are presented and discussed. In order to answer more efficiently to present needs in agriculture a better organisation and communication between research, extension and farmers is needed; Produire durablement en milieu tropical humide impose de nombreux challenges à l’agriculture : il faut atténuer les contraintes liées aux sols et au climat, lutter contre la pression de maladies et ravageurs, répondre aux besoins nutritionnels des plantes tout en économisant les ressources du milieu et en limitant les intrants onéreux, le plus souvent mal adaptés et potentiellement polluants. L’INRA a, dès le début des années 80, mis en place des recherches et proposé des innovations pour tenter d’apporter des réponses spécifiques aux problèmes rencontrés au sein des milieux et des cultures tropicales. La transposition de résultats acquis ailleurs ayant montré ses limites, les réponses ont été élaborées grâce à la compréhension du fonctionnement des systèmes et ont consisté à orienter avec prudence le fonctionnement des sols par les amendements et la gestion de la matière organique, maintenir des conditions favorables à la nutrition et la protection des cultures par l’utilisation de paillages et de plantes associées ou développer des procédés de lutte biologique et de nouvelles variétés. Des innovations réalisées dans ces domaines pour les cultures vivrières et maraichères de Guadeloupe et Martinique sont présentées et discutées. Pour répondre aux nouveaux enjeux du développement agricole, le gain apporté par la capitalisation des connaissances apparaît clairement et plaide pour un meilleur partage entre les acteurs.

National audience; Agro-ecological innovations are needed to reduce the impacts of current intensive agricultural practices on biodiversity and ecosystems. Whereas many published studies focus on the biophysical impacts of such innovations at field level, few attention has been given to the analysis of the potential of adoption of these innovations at farm and regional levels. In order to reduce the gap between on station and in silico innovation and farmer’s adoption process, we developped an interdisciplinary method based on the combination of simulations models and on farm surveys to assess ex ante the potential of adoption of agro-ecological innovations by farmers.

Aim of the study The aim of this study was a comparison of popular household remedies in primary health care in the communities of Terre-de-Haut and Terre-de-Bas, the inhabited islands of ‘Les Saintes’ archipelago (Guadeloupe, French West Indies). Methods Twelve ailments, with higher prevalence, were chosen in each island and a total of 216 families were interviewed using TRAMIL participative ethnopharmacological interviews. Results According to TRAMIL methodology (frequency over 20%), twenty-two plants uses were recorded for Terre-de-Haut and eighteen for Terre-de-Bas. The islands share only ten significant plants uses and four of them have notable different frequencies. The informant consensus factor in the use of many specific remedies was fairly high, that gave an additional validity to these popular medicines. Conclusion The data presented in this study show that popular knowledge on medicinal plants uses is still alive in the studied area. The difference between the two nearby islands is very narrow but on the other hand, there exist some differences possibly due to a probable declining of plant resources and a more important flux of migration and its provision of other practices of healthcare in Terre-de-Haut.

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; The ex ante assessment of innovative agro-ecological innovations is a key step in the development of more sustainable crop management systems. To this end, models are useful tools because they make it possible to rapidly assess numerous innovations in different contexts. Whereas many farm optimisation models focusing on the farmer’s strategic decision to adopt new crop management systems have been published, little attention has been given to the ex ante modelling of the dynamic operational impacts of innovation adoption at the farm level. BANAD, a mechanistic model for such applications,is proposed. It allows the ex ante assessment of innovative management systems including new agroecological techniques, while taking into account different farming contexts and policy and market conditions. It includes three components: (i) a crop management system model, (ii) a crop model (SIMBA) and (iii) a farming system model. Our results applied to the ex ante assessment of six innovative banana management systems for three contrasted farm types in Guadeloupe showed that the impacts of agroecological innovations, which include rotations, improved fallow, intercropping, pest-resistant cultivar, and an integrated organic system, can vary considerably according to (i) the farm type in which the innovation is integrated, (ii) the nature of the agro-ecological innovations, and (iii) the criteria considered and the temporal horizon of the assessment. Innovative intercropping systems that were effective at the field level in terms of the yield improvement and decreased pesticide use could be problematic at the farm level because they increased the workload and decreased income. The adoption of rotations or improved fallow seemed to be relevant for smallholders but could induce a critical period of 1.5–2.5 years during which income decreased drastically. Under certain conditions of markets and subsidies, very environmentally friendly innovations that are less productive can however be economically effective.

International audience

International audience