Effet du greffage horticole et de l’inoculation mycorhizienne sur la croissance du baobab (Adansonia digitata L.) en Moyenne et Haute Casamance (Sénégal)

L’objectif de ce travail est d’étudier l´effet du greffage et de l’inoculation mycorhizienne sur la croissance du baobab dans les régions de Kolda et de Sédhiou. Pour ce faire, un dispositif experimental en bloc aléatoire complet constitué de quatre traitements sur des plants de baobab (greffé inoculé, greffé non inoculé, non greffé inoculé et non greffé non inoculé) a été mis en place dans huit (8) sites. Le greffage a été effectué avec la méthode de fente terminale et l’inoculation avec un mélange de souches de champignons mycorhriziens arbusculaires (Glomus aggretatum, G. intraradices et G. Fasciculatum) en pépinière. Deux ans après plantation, les traitements ont montré que les plus gros diamètres et le plus grand nombre de rameaux sont obtenus avec les plants greffés (inoculés et non inoculés) alors que les hauteurs les plus élevées avec ceux non inoculés (non greffés et greffés). Le nombre de feuilles le plus imporatant est observé sur les plants non greffés non inoculés. Par ailleurs, des différences significatives entre les sites ont ausssi été constatées. Tel est le cas pour les taux de coissance selon les lequels pour la plupart des sites les plants non greffées inoculés donnent les meilleurs résultats en hauteur et en diamétre. L’inoculation n’a pas eu d’effet significatif. Les résultats de cette étude contribueront à une meilleure maîtrise des techniques de raccourcissement du cycle de production du baobab, par conséquent, au développement de politiques de rajeunissement des parcs à baobab au Sénégal pour mieux répondre à la demande du marché national et international de plus en plus croissant. The aim of this work is to study the effect of grafting and mycorrhizal inoculation on recovery, survival and success rates and on certain baobab growth variables in the Kolda and Sedhiou regions. To do this, a complete randomized experimental block consisting of four treatments on baobab plants (grafted inoculated, grafted uninoculated, ungrafted inoculated and ungrafted uninoculated grafted) was placed in eight (8) sites. Grafting was performed using the terminal slit method and inoculation with a mixture of archaeal mycorrhizal fungi strains (Glomus aggretatum, G. intraradices and G. Fasciculatum) in the nursery. Two years after planting, the largest diameters and the largest number of branches are obtained with the grafted plants (inoculated and uninoculated) whereas the highest heights with those not inoculated (ungrafted and grafted). On the other hand, the number of leaves did not give any significant difference. Moreover, there are significant differences between the sites related inter alia to their mode of management. This is the case of the growth rates, which ungrafted inoculated plants have the more important diameter and height in most of the sites. There is no significant effect‘s inoculation. The results of this study will contribute to a better control of the techniques of shortening the cycle of production of baobab by horticultural grafting and, consequently, to the development of rejuvenation policies of baobab parks in Senegal to better meet the demand of the national market and more and more international

Fonctionnement Hydrique du Baobab (Adansonia digitata L.) en Moyenne et Haute Casamance (Sénégal)

Cette étude aborde le fonctionnement hydrique du baobab afin de mieux appréhender ses relations en eau avec ses phases phénologiques et l’effet induit par les saisons climatiques et de celui de la toposéquence. Pour cela, l’humidité du sol, la teneur relative en eau (TRE) et le potentiel hydrique foliaire (Ψ) ont été étudiés. Les données ont été collectées sur deux sites, en plateau et dans le bas-fond, en saison sèche chaude (SSC), en pleine saison des pluies (PSP) et en saison sèche fraiche (SSF). La SSC correspond à l’apparition des premières feuilles. La PSP correspond à la pleine feuillaison et la fin de la floraison et au début de la fructification. La SSF correspond à la maturation avancée des fruits et à la pleine chute des feuilles. Le logiciel R version 3.4.2 a été utilisé pour traiter les données. Il a permis d’effectuer des tests pour l’analyse des données. Les résultats montrent une variation saisonnière de l’humidité du sol autour de la zone racinaire du baobab. En effet, en SSC, l’humidité du sol est à son niveau le plus faible contrairement en MSP et en SSF. Cependant, la faible disponibilité en eau du sol en SSC n’empêche pas l’état hydrique interne du baobab d’être élevé. En effet, espèce caduque à tronc succulent, les Ψ et les TRE trouvés du baobab sont plus élevés en saison sèche qu’en saison pluvieuse. Egalement, en fonction des saisons climatiques, les différences obtenues sur les Ψ d’une part, et sur les TRE d’autre part, sont statistiquement significatives (P<0,05) sur le plateau contrairement au bas-fond. Ce dernier bénéficie des conditions hydriques du sol plus favorables pendant la saison sèche, ce qui a probablement minimisé ces différences, d’où le rôle important de la toposéquence sur la recharge de l’eau du sol. Ces résultats sont importants dans le but de mieux encourager la propagation les plantations de baobab grâce à sa capacité d’adaptation aux saisons climatiques et au milieu, et de sa tolérence à la sècheresse saisonnière du sol, afin de palier la dégradation de la ressource et faire face aux effets du changement climatique. This study deals with the baobab's water functioning in order to better understand its water relations with its phenological phases and the effect induced by the climatic seasons and that of the toposequence. For this, the soil moisture, the relative water content (TRE) and the leaf water potential (Ψ) were studied. Data were collected at two sites, in the upland and in the lowland, in the hot dry season (SSC), in the middle of the rainy season (PSP) and in the cool dry season (SSF). SSC corresponds to the appearance of the first leaves. The PSP corresponds to full leafing and the end of flowering and early fruiting. SSF is the advanced ripening of fruits and the full fall of leaves. The R version 3.4.2 software was used to process the data. It allowed to test the data analysis. The results show a seasonal variation ofsoil moisture around the baobab root zone. Indeed, in SSC, soil moisture is at its weakest level, unlike in MSP and SSF. However, the low water availability of soil in SSC does not prevent the internal water condition of baobab from being high. Indeed, succulent trunk deciduous species, Ψ and TRE found baobab are higher in the dry season than in the rainy season. Also, according to the climatic seasons, the differences obtained on Ψ on the one hand, and on the TREs on the other hand, are statistically significant (P <0.05) on the upland contrary to the lowland. The latter benefits from more favorable soil moisture conditions during the dry season, which probably minimized these differences, hence the important role of toposequence on groundwater recharge. These results are important in order to better encourage the spread of baobab plantations through its ability to adapt to the climatic seasons and the environment, and its tolerance of seasonal soil drought, in order to mitigate the degradation of the resource and cope with the effects of climate change

Le cactus Opuntia tuna (L.) Mill. et ses formes d’usage dans la zone des Niayes au Sénégal

Opuntia tuna est une espèce bien adaptée dans la zone des Niayes au Sénégal. Sa prolifération assez rapide est due en partie à une sous exploitation suscitant ainsi un envahissement de quelques espaces agropastoraux. Dans une perspective de valorisation et de meilleure gestion de l’espèce, cette présente étude a été conduite pour comprendre les formes d’usages et de gestion de la plante par les populations locales afin de la promouvoir pour renforcer leur résilience. L’étude a porté sur cinq villages de la zone nord des Niayes auprès de petits exploitants de maraichers. Des enquêtes qualitatives par entretiens et groupes de discussion ont été conduites. Elles ont porté sur le niveau de connaissance, les pratiques et usages connus du cactus, les contraintes liées à sa présence, les solutions adoptées ou envisagées et le niveau de perception sur sa valorisation. Les résultats ont révélé de nombreux usages de la plante et de ses produits. Plus de la moitié des personnes enquêtées utilise le cactus dans le domaine agricole. L’élevage, la pharmacopée et l’alimentation sont d’autres secteurs également concernés par l’usage du cactus. Les analyses ont montré que la plupart des personnes enquêtées (94%) admettent un degré d’envahissement très élevé de Opuntia tuna. Le niveau d’envahissement pourrait être liée à la zoochorie selon 38% des hommes et 33% des femmes. La bonne adaptation de l’espèce dans la zone serait également un facteur de prolifération selon 33% des hommes et 23 % des femmes. Afin de pallier la prolifération rapide du cactus les maraichers ont développé des stratégies de gestion telles que le brulis, la coupe et le dessouchage. Une meilleure gestion de cette espèce qui présente de nombreux usages pour les maraichers de la zone des Niayes est nécessaire. De tels usages de l’espèce, valorisés davantage pourrait contribuer de façon significative à la diversification des sources de revenus des communautés locales et au développement durable de la zone des Niayes

Reforestation and sylvopastoral systems in Sahelian drylands: evaluating return on investment from provisioning ecosystem services, Senegal

International audienceSince the 1960s, droughts have caused significant degradation of Sahelian ecosystems, particularly resulting in a reduction in tree cover. Despite the challenges posed by climate change, the rural Sahelian population continues to depend on natural resources for pastoral livestock farming, which remains a critical source of livelihood. To address this issue of land degradation, Sahelian states and international coalitions are prioritizing efforts to restore pastoral land through reforestation programs. These initiatives aim to enhance ecosystem services, generate new income for the population, and safeguard biodiversity.In practice, however, reforestation has often led to a depletion of resources for communities due to enclosure policies. This paper explores various land management models for reforestation within a pastoral context through provisioning ecosystem services (PES) modeling.This study quantifies the economic potential of PES offered by reforestation programs in Senegal. It employs a quantitative methodology to assess the profitability of these operations from the perspective of pastoral economies. The analysis reveals that the PES benefits of reforestation can significantly enhance the economic potential of sylvo-pastoral productions if resource access is negotiated collaboratively between pastoralists and forestry extension services during reforestation activities and after. From an investment perspective, the economic viability of reforestation operations in drylands is questionable. The findings suggest that when evaluated solely in terms of PES profitability, these programs may not be financially sustainable. The sustainability of these investments would require taking into account supporting and regulating ecosystem services

Dynamique de l’occupation du sol de la commune de Téssékéré de 1984 à 2015 (Ferlo Nord, Sénégal)

International audienc

Efficacy of two anthelmintics against gastrointestinal nematodes of sheep in the silvopastoral zone of Senegal, Mali and Burkina Faso

Gastrointestinal nematodes (GIN) are a major impediment to sheep health and productivity. Frequent use and under dosing of chemical anthelmintics (AH) have led to the development of GIN populations which are resistant to these drugs in many parts of the world. In West Africa, the importance of GIN infections in sheep is poorly documented and the potential problem of AH resistance is neglected. We therefore conducted an on-farm study to determine the efficacy of two AH (Albendazole and Ivermectine) that are frequently used in Mali, Burkina Faso and Senegal, the focal countries of the EU-funded project SustainSahel. Sheep carrying natural GIN infections were selected from another study on GIN prevalence and infestation intensity. In each country, 24 male sheep with a minimum faecal egg count of 500 eggs per gram were selected for the efficacy study. Sheep were randomly allocated to 3 treatment groups of 8 animals: Ivomec® (Ivermectin), Valbazen® (Albendazole), and Control (without treatment). AH doses were administered according to the manufacturers’ instructions after weighing the animals, namely Valbazen (oral) at 7.5 mg kg-1 body weight, Ivomec (subcutaneous) at 0.2 mg kg-1 body weight. The faecal egg count reduction test (FECRT), as recommended by World Association for the Advancement of Veterinary Parasitology, was used to determine anthelmintic efficacy. For Ivomec®, FECR were 97 %, 95 % confidence interval (CI) (89%-100 %); 97 %, CI (93%-99 %) and 56 %, CI (24%-76 %) in Burkina Faso, Mali and Senegal, respectively. These results point to AH resistance of GIN to Ivermectin in Burkina Faso and confirm resistance to this drug in Senegal. In Mali, however, ivermectin did not show reduced efficacy. For Valbazen®, FECR were 99 %, 95 % CI (96%-100 %); 100 %, CI (99%-100 %) and 75 %, CI (43%-90 %) in Burkina Faso, Mali and Senegal, respectively. This corresponds to full efficacy of Albendazol in Mali and Burkina Faso and AH resistance in Senegal. We conclude that GIN resistance to both anthelmintics is present in the study region. The use of alternative treatment options, such as by secondary plant metabolites, could be a future control option to reduce the progress of resistance towards allopathic anthelmintics

Prevalence and intensity of gastrointestinal nematode infection in small ruminants in three West African countries

This study was carried out to provide missing information on the prevalence and intensity of gastrointestinal nematode (GIN) infections of small ruminants in three West African countries. The use of communal grazing areas in these countries favours the spread of GIN infections across small ruminants and may reduce production performances and herders’ income. Faecal samples of 1,235 small ruminants were collected in Burkina Faso, Mali and Senegal in late dry (May), rainy (August) and early dry (November) season of 2022. Individual Faecal Egg Counts (FEC) were performed by a modified McMaster technique. Animals were selected in several villages according to the following parameters: species (sheep, goats), age (young: 6–12 months, adult: >12 months) and sex (male, female). The Kruskal-Wallis test was applied to assess the influence of these parameters on FEC intensity, expressed as eggs per gram of faeces (EPG). The overall prevalence of GIN was 70.8 %, 82.6 % and 66.8 % in Burkina Faso, Mali and Senegal, respectively. In all countries, the rainy season corresponded to the highest infection period. The mean ± standard deviation of EPG across all countries was 230 ±350, 1,023 ±1,176 and 424 ±352 for late dry, rainy and early dry season. Infection intensity was higher in young than in adult animals, and in male than in female animals in the rainy season, whereas no differences could be observed between these groups in the late dry season. Similarly, there was no significant difference in the mean EPG between sheep and goats late dry season. The results indicate that better monitoring and control of GIN infections are necessary during the rainy season and especially in young and male sheep and goats. For further study it would also be interesting to learn more about anthelmintic resistance in GIN and non-allopathic control options

Grazing with trees

Trees in dryland forests and wooded areas provide key ecosystem services such as animal feed, timber, fruits and, regulation of soil and water cycles. Equally, the presence of livestock in dryland woody areas can also play an important role in the local ecosystem; not only are they a source of income for local communities, but they also help vegetation and mobilise stored biomass. When both of these ecosystem elements are wisely combined – livestock and trees – it creates an integrated agricultural system that can boost the local ecosystem, representing a welcome agro-ecological transition in livestock farming. The ‘Grazing with Trees’ report gives a thorough assessment of the positive role that optimized extensive grazing livestock farming can play in the management and restoration of drylands’ forests and lands with trees. It assesses and provides sound evidence on the benefits of applying an integrated landscape approach and utilizing farmers and pastoralists’ knowledge to halt desertification, increase resilience, and enhance food security under the actual changing scenario. The report confirms the importance of agroforestry as a primary pathway for forest restoration in dryland areas as recommended by FAO’s State of Forests 2022, and its recommendations encourage landscape planners and decision makers to consider livestock as allies, carefully restore tree cover and accelerate action to promote healthy ecosystems

Use of trees and shrub by farmers to control gastrointestinal nematodes (GIN) in extensive livestock production systems of West Africa

Traditional veterinary practices have taken a back seat to modern veterinary medicine in livestock health management in Africa. However, the latter is not able to cope with all health problems on livestock farms, especially in rural areas where access to quality veterinary drugs and services is not available. Adding to this is the low purchasing power of livestock farmers. They are forced to resort to traditional practices to treat their animals in case of disease, which is especially true for gastrointestinal nematodes (GIN) in small ruminants. This study aimed to identify, with the herders, the local woody plant species usually used to treat parasitic infections of small ruminants in West Africa. Indeed, in traditional medicine, woody species represent about 65 % of the most important African medicinal plants. An ethno botanical survey based on semi-structured interviews was conducted with 370 herders and agropastoralists in Senegal, Mali and Burkina Faso between June and July 2021. More than 60 % of the respondents stated that the use of tree-based remedies has a positive impact on animal health. Out of 81 herders surveyed in Senegal, 42.0 % used woody plants for animal health treatment. In Burkina Faso, 28.7 % out of 159 farmers used ligneous plants to treat their animals against gastrointestinal strongyles. In Mali, 16.4 % out of 130 farmers used parts of trees to treat small ruminants against GIN. Across the three countries, 20 woody species belonging to 10 botanical families were identified as being regularly used to treat GIN. Khaya senegalensis, Azadirachta indica and Faidherbia albida were the most commonly cited species, and at family level Fabaceae (67 %) dominated before Meliaceae (17 %) and Combretaceae (17 %). Leaves (50 %), pods (33 %) and bark (17 %) were the organs mainly used to produce herbal anthelmintics. The cross-country comparison of results revealed that, although farmers have a good knowledge of effective plant-based GIN control, preparation formulae and application doses are often variable and only mastered by a few users. In view of smallholders’ reliance on herbal medicine, more effort should be devoted to tap the potential of woody plants as alternative remedies for the treatment of GIN in sheep and goats