Portail "HAL-Francophonie Afrique et Océan Indien"
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Formes de l’azote dans les sols cultivés des exploitations maraîchères des zones (péri) urbaines des villes et Franceville et Moanda au Sud-Est du Gabon
No full textInternational audienceL’étude du suivi des formes d’azote dans les sols des exploitations maraichères de Franceville etMoanda, au Sud-Est du Gabon a pour enjeu de réduire l’empreinte écologique des pratiques culturales. Au total194 échantillons dans 40 profils ont été prélevés dans les sols cultivés en haut, mi et bas de pente, à cinqprofondeurs (0-20 ; 20-40 ; 40-60 ; 60-80 et 80-100 cm). L’analyse de la variance au seuil 0,05 a montré dedifférences significatives sur les paramètres mesurés (granulométrie, pH, azote total, azote ammoniacal etnitrates). Les sols de deux sites ont un pH acide (4,5 et 5). A Franceville, le taux de sables est élevé en surface.A Moanda le taux d’argile est deux fois plus élevé en profondeur qu’en surface. L’azote total et ammoniacalsont respectivement concentrés en bas de pente dans la couche 0-20 cm, soient 0,10 ± 0,0258% et 0,006 ±0,0016% à Franceville ; 0,08 ± 0,0121% et 0,004 ± 0,0011% à Moanda. Les teneurs en azote ammoniacal sontdeux fois plus importantes à Franceville qu’à Moanda. La plus forte teneur 15 ± 14,95% des nitrates a étéobservée à Moanda, dans la couche 0-20 cm, en haut de pente. A Franceville, elle a été de 10 ± 9, 83% en hautde pente à 40-60 cm. La présence des formes d’azote dans les couches profondes et en bas de pente pourraitconstituer une source de contamination des eaux des nappes et des rivières
Enhancing microclimate modeling in tropical climates: validation of Envi-Met with experimental data from Reunion Island
No full textInternational audienceUrban microclimate modeling is essential for planning future developments to adapt to climate change. Tools like ENVI-met, developed in Germany, have been widely validated in temperate climates, but have only rarely been comprehensively evaluated in tropical environments, especially across multiple urban climate parameters relevant to thermal comfort. This study evaluates Envi-met using a network of ten lowtech weather stations deployed in a neighborhood of Réunion Island. The results show good agreement for air temperature (M AE ≈ 1°C, R 2 ≈ 0.8) and relative humidity (R 2 ≈ 0.6), and acceptable performance for radiation. However, wind speed is systematically overestimated (M AE ≈ 2m/s), which may affect thermal comfort indices. Despite this, ENVImet remains a suitable tool for supporting UHI mitigation strategies in tropical urban planning. Key Innovations• First validation of Envi-met model in tropical climate of Reunion Island over an extended 72hour period with a dense network of measurement points. • Holistic validation of ENVI-met with multiple parameters (temperature, humidity, wind, radiation and outdoor thermal comfort) and multiple sensors over two seasons. • Analysis of wind speed and radiation biases, often overlooked in previous studies, to better understand their impact on thermal comfort indices like UTCI. Practical ImplicationsENVI-met has proven to be a reliable tool for assessing urban heat island mitigation strategies in tropical climates. However, accurate input data, especially for wind and radiation, remain essential, as misestimations can distort thermal comfort results and compromise urban design outcomes.</p
Optimal pest control for banana production under varying infestation density
No full textBanana and plantain production faces significant caused by many pests, the most harmful being Radopholus similis. This nematode infests and spends most of its life in the plant roots, which makes it difficult to control. Conventional methods face efficiency, cost, and environmental limitations, making it crucial to design optimized strategies. Our aim is to tackle this issue by formulating an optimal control problem on an original model of banana-pest interactions.We propose a four-compartment model describing the host and pest dynamics. Its originality is that both infected roots and infesting nematodes are considered, which allows variable nematode densities in the roots. By employing time-scale separation, we reduce the model dimension and reveal a scenario where both stable pest-free and endemic equilibria coexist (backward bifurcation). We then include a control variable which reduces the root infestation rate. We formulate an optimal control problem aiming at maximizing the profit during a cropping season. The existence of an optimal control and necessary optimality conditions are established. We solve the optimal control problem by a direct method implemented in Bocop. For numerical settings of interest, the optimal solutions exhibit a bang-bang quasi-periodic structure. We extensively test whether candidate suboptimal strategies, based on periodic or constant control, can approximate the optimal performance. Numerical comparisons reveal that constant control performs poorly, whereas periodic control closely approaches the optimal solution. This confirms the overyielding effect and supports the realistic implementation of periodic control.</p
Evaluation of Different Group Formation Methods in the Context of Distributed Pair Programming: Design and Experiment in Higher Education
No full textInternational audienceGroup formation is an important issue in collaborative learning, as properly formed groups can lead to better interactions between students and enhance their learning. This issue also applies to pair programming when it is used as a learning activity. When the number of students is important and/or students and teachers do not know each other very well, manual group formation, either by students or teachers, can become difficult. Many of the existing automatic methods used for automatic group formation in pair programming require a certain amount of personal information about the students, which can make the implementation of this kind of system difficult. Hence, in this paper we present an automatic pair formation method integrated to a distributed pair programming application. Our approach is based on personal data from the students collected with questionnaires within our platform, but also on trace data automatically collected from the pair programming activities completed by students. It has been experimented during an introductory programming course in higher education. The objective was to identify, among programming experience, self-efficacy, gender and past engagement in pair programming activities, the formation criteria that led to the best perceived compatibility and work distribution as well as performance. The results show that homogeneous pairs in self-efficacy are significantly better than heterogeneous pairs, both in terms of perceived compatibility and perceived work distribution
Colonial transition as a major mediator of global health transition: lessons from the 2024 New Caledonia crisis
No full textInternational audienceNew Caledonia is currently seeking its future institutional framework through violent, politically-driven clashes within the population. The insurrections in May 2024, fuelled by political, and social divisions, also targeted the healthcare system in an unprecedented manner. Here we summarise the situation from a global health perspective and outline its link with colonial transitions. The territory now faces new health-related challenges because of trends in ageing (due to demographic transitions) and the transition from infectious to noncommunicable diseases (NCDs), especially due to disparities between ethnic groups. Research has shown the Melanesian (Kanak) and Oceanian populations had a higher average body mass index than European (P < 0.001). Simultaneously, the incidence of leptospirosis (which is associated with rainfall) in 2021–22 were higher in the communal district where the Kanak group formed the majority of the population, compared to the western and southern coasts, where European people lived. Among the NCDs, issues with mental health predominate the literature, especially among the young, males, and the Kanak population. We therefore call for a deep consideration of this problem, considering all the cases that are emerging due to the new civil unrest that targeted all the society. Simultaneously, the 2020 and 2021 referendums for independence during the COVID-19 pandemic lockdowns revealed the deep-seated impacts of global health transition embedded within the colonial trauma, as disease control and its consequences were an essential prerequisite for the political debate. These vulnerabilities highlighted the urgency for targeted interventions, necessitating an approach adapted to community care that respects the New Caledonia people’s cultural practices. We also call for a field-based experimental approach that must emphasise sustainable health, inequality reduction, the One Health approach, and climate change. Ultimately, integrating sociological insights into health policies is crucial for restoring dignity, addressing trauma, and preparing for future crises, fostering a more inclusive and resilient society
A ribodepletion and tagging protocol to multiplex samples for RNAsseq based virus detection: Application to the cassava virome
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/614116/)International audienceBackground: Cassava (Manihot esculenta, Crantz), is a staple food and the main source of calories for many populations in Africa, but the plant is beset by several damaging viruses. So far, eight families of virus infecting cassava have been identified; the Geminiviridae (ssDNA viruses responsible for cassava mosaic disease, CMD) and Potyviridae (ssRNA + viruses responsible for cassava brown streak disease, CBSD) families being the most damaging to cassava in Africa. In several cassava-growing regions, the co-existence of species and strains from these two families results in a complex epidemiological situation making it difficult to correctly identify the viruses in circulation and delaying the implementation of disease management schemes. Nevertheless, the development of next generation sequencing (NGS) methods has revolutionized plant virus detection and identification. One NGS method that has been successfully used in virus detection and identification is ribodepleted RNA sequencing. Unfortunately, the relatively high cost makes it difficult to upscale this method to large epidemiological surveys and limits its adoption as a diagnostic tool. Results: Here, we develop a high-throughput sequencing protocol, named Ribo-M-Seq, that combines plant rRNA ribodepletion, cDNA synthesis, tagging with a 96 multiplexing scheme and Illumina sequencing. We evaluated the protocol on a series of cassava samples with a known assemblage of viruses. After confirming that the protocol was suitable for ribodepletion, we demonstrated it was possible to detect RNA and DNA viruses via identification of near full-size genomes. Additional phylogenetic analyses confirmed the presence of begomoviruses and ipomoviruses responsible for CMD and CBSD, respectively. We also detected a recently described ampelovirus (Manihot esculenta-associated virus) that was not detected in previous analyses. Conclusions: The use of the Ribo-M-Seq protocol will pave the way for large-scale sample analyses of collections with potentially complex viromes, such as those collected in the West African cassava integrated pest management program
An organizational capacity self-assessment for innovation support service providers (OCATI) - approach and results from application in Madagascar
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/614022/) * Autres projets (id;sigle;titre): LEAP-AGRI-273;SERVInnov;(EU) Strengthening Innovation Support SERVices to enhance INNOVations for sustainable food production//International audiencePurpose: This paper introduces the Organisational Capacity Assessment Approach for Innovation Support (OCATI) and presents findings from its application with a farmer-based organisation in Madagascar. Design/method/approach: OCATI has been co-designed within the EU–Africa collaborative research project SERVInnov, reflecting conditions in the global South, particularly Madagascar, Cameroon, and Burkina Faso. It assesses organisational, technical, and functional capacities, skill needs, and structural conditions for delivering innovation support services (ISS). Findings: Results from its application in Madagascar, show disparities in performance across five capacity components with the highest performance in delivering ISS and the weakest in networking and policy engagement. Recommendations include initiating policy lobbying, institutionalisation, updating knowledge of the innovation ecosystem, new collaborations, ISS mapping tools, and clear communication channels. More so, enhancements in risk management, service diversification, human resource expansion, and ISS-type awareness are equally seen as crucial. Theoretical implications: Realising an OCATI assessment fosters organisational evolution, complements widely used monitoring and evaluation (M&E) tools, and supports experiential learning approaches for extension and advisory service (EAS) organisations. Practical implications: Practically, the results provide an opportunity for reflexive thinking about organisations' own position in supporting innovation, raising awareness for ISS, and revealing how support for innovation processes in agriculture matters and can be enhanced. The approach help organisations extract and develop core competencies in innovation support, thereby becoming more professionalised and recognised. Original Value: This study addresses a significant research gap in organisational capacity assessment for innovation support and introduces a novel self-assessment tool for use by innovation support service providers
Utilisation de biochars riches en silice pour la protection des cultures contre les insectes ravageurs : potentiel et processus
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/613871/) * Autres projets (id;sigle;titre): ;;(EU) DPP SantéBiodiv//International audienceL'effet de l'apport au sol de biochars riches en silice (sichars), a été évalué sur trois pathosystèmes : puceron jaune Sipha flava sur sorgho ; chenille légionnaire d'automne (CLA) Spodoptera frugiperda sur maïs ; noctuelle Helicoverpa armigera sur soja. Ont été comparés à un témoin sans apport : B+) un sichar de balle de riz de Camargue ; B-) sa fraction sans silice ; Si) la silice pure extraite de cette balle de riz ; BA) un sichar de balle de riz de Madagascar. Ont été mesurés : i) la biomasse aérienne des plantes ; ii) la croissance/développement des ravageurs et les dégâts foliaires ; iii) les paramètres électrochimiques (pH, potentiel redox, conductivité électrique) sur feuilles par spectrométrie proche infra-rouge (SPIR) ; iv) les teneurs en silice et azote des plantes. BA et B+ ont favorisé le développement des trois plantes. B- et Si ont négativement affecté le développement respectivement du seul maïs et du seul soja. Le PJC n'a été affecté par aucun traitement. Si et B+ ont défavorisé les deux noctuelles. B- et BA ont défavorisé la CLA, mais favorisé H. armigera. Sur maïs, tous les apports ont oxydé les plantes, davantage les sichars que B- et Si. BA a significativement augmenté la teneur en silice du sorgho, alors qu'aucun effet des traitements n'a été observé sur soja. Les potentiels des sichars en tant qu'innovations pour le biocontrôle, et des mesures électrochimiques par SPIR comme indicateurs de stress/homéostasie des plantes face aux ravageurs, sont discutés
