Ferralsols of southern Côte d'Ivoire under strong land pressure: What alternative to an improving soil fertility for a sustainable cassava production?

Abstract A study carrying on the morphological and physical properties of soils has been conducted in the South of Côte d'Ivoire, in the locality of Dabou. This region is submitted to a strong land pressure and a competition between food and industrial crops. This competition took place to the detriment of cassava on ferralsols poor in organic matter. In order to understand the behavior of these soils, the main physical parameters have been described. The transects of about 300 m were opened in three villages and the pedological profiles have been described on a scale of 1/5000. The pH has especially been put in evidence because the soils under industrial crop are frequently fertilized to the detriment of food crops. The studies put in evidence an acidification phenomenon of the ferralsols. The soils were modal ferralsols or typical in absence of coarse element. It has also been noted an enrichment of the soils in thin element in depth but neither of cuirassing nor compactness. The morphology of soil was not a constraint for plant but an important constraint bound to the acidification of soils exists. To overcome this constraint, the use of organic manure was recommended in a good cropping system

Morphopedological Characteristics of Soils under Shea Trees in the Bouna Region of Northeast Côte d'Ivoire

The present study was initiated to characterize the soils of three (03) ecological zones of natural establishment of shea in the region of Boukani, in the north-east of Côte d'Ivoire. The study consisted of opening soil pits for morphological characterization following the approach of the Office of Scientific and Technical Research Overseas, based on in situ observation. Botanical data such as density per square meter, trunk diameter at 1.30 m from the ground and their spatial arrangement were also collected. The areas concerned are the villages of Gnarkèradouo, Assoum 2 and Nakélé. The results observed show a significant difference between sites. The shea park is denser in Gnarkèradouo (44.16%), followed by the Assoum 2 park with 38.32% of shea trees and finally the Nakélé site where 17.52% are observed. For the circumference of trees at 1.30 m from the ground, the results show that it is at Nakélé that large trees are observed with high values of 144 cm, then at Assoum 2 (126.2 cm) and finally at Gnarkèradouo with 114.8 cm. The characteristics of the soils show similarities on the 3 sites. These are gravelly soils with obstacles (indurations). However, the soil at Assoum 2 appears to be different because it is deep. The texture is sandy-clay on all three sites

Assessment of low-input technologies to improve productivity of early harvested cassava in Côte d'Ivoire

In Cote d'Ivoire, smallholder farmers cultivate cassava on poor, highly weathered soils without improved varieties or fertilizer inputs. Land pressure combined with high demand result in premature harvests and low yields. Furthermore, subsistence agriculture limits the adoption of input-intensive technologies. This study aimed at identifying integrated soil fertility management systems for increasing cassava productivity and profitability in two locations in southern Cote d'Ivoire. The integrated technical interventions included improved cassava genotypes and modified spacing, legume intercropping, and application of fertilizer at moderate doses. Overall, an improved cassava variety (Yavo) generally out-yielded the other varieties at both sites. Legumes performed better at the higher soil fertility site and gave higher grain yield and biological nitrogen fixation in a 2x0.5m cassava spacing compared to 1x1m. The response of cassava to nutrient amendments varied between sites, suggesting the need for site-specific adaptations. Fertilizer application was essential to avoid cassava yield reduction upon legume intercropping as a result of competition for nutrients and N immobilization and delayed re-mineralization of legume residues. Growing legumes, however, substantially increased profitability. Hence, better synchronization of legume sowing, legume residue and fertilizer application in relation to cassava growth phases is needed

Plantain mycorrhization with native consortium of arbuscular mycorrhizal fungi (AMF) induce solubilisation of metals (Fe2+ and Al3+) in soil from Azaguié (south-east of Côte d’Ivoire)

New agroecological practices propose to manage soil fertility using soil microorganisms such as arbuscular mycorrhizal fungi (AMF). However, few studies have been conducted on the impact of plantain mycorrhization and metal (Fe2+ and Al3+) solubilisation in soil. This study evaluates the effectiveness of native AMF on plantain growth and metal leaching from soil. Trap plants (maize, sorghum and cowpea) were grown to produce various inoculums. Then, plantains were grown under controlled conditions, with six treatments (control, plantain without inoculum, plantain with maize root inoculum, vigna root inoculum, sorghum root inoculum and mixed root inoculum) replicated five times. Growth parameters were measured, and the rate of plantain root colonization was evaluated by determining the frequency or intensity of infection. The contents of metals in leached solutions were analyzed using ICP-OES. Results indicated the rate of plantain roots colonization by fungi was not significantly different between the different treatments. Plantain biomass remained very low whatever the treatment. However, plant inoculated with vigna roots inoculum had the highest biomass while plant inoculated with sorghum root inoculum showed the lowest biomass. Leached solutions from soils with inoculated plants had on average a pH value of one pH unit lower than leached solutions from soils without inoculum. In addition, plantain mycorrhization can promote the leaching of Fe2+ from the soil by acidification, whereas the difference between treatments was not significant for the concentration of Al3+ in solutions. These results suggest that the association of plantain with microorganisms remains a way for agroecological banana production in Côte d’Ivoire

Intensification pathway for improvement of smallholder cassava production systems in Southern Côte d'Ivoire

In order to intensify cassava production in southern Cote d'Ivoire, multiple farmers' field trials were carried out in two important cassava-producing areas (Dabou and Bingerville). The effectiveness of an Integrated Soil Fertility Management (ISFM) approach as intensification pathway was evaluated for poor sandy soils. Overall, ISFM-based systems outperformed the local cultivation system. The average cassava yield was 14.5 and 6.5 t ha(-1) and 12.6 and 5.7 t ha(-1) for the ISFM and traditional systems, in Dabou and Bingerville, respectively. The average profitability of ISFM systems was ca. 2500 Euro ha(-1), whereby 66% was generated by cowpea intercrop, which yielded on average 3.1 t ha(-1). Taking into account the limited farmer's resource endowment and poor soil fertility, ISFM is a crucial component for sustainable intensification of cassava production and poverty alleviate in southern Cote d'Ivoire

Evaluation du Potentiel Mycorhizien des sols Pollués de la Décharge M’Ploussoue de Bonoua, Côte D’Ivoire

L’accumulation de substances toxiques telles que des éléments traces métalliques (ETM) dans les sols du site de la décharge de M’Ploussoue de Bonoua pourrait affecter la prolifération des microorganismes plus spécifiquement la sporulation et la germination des spores des Champignons Mycorhiziens à Arbuscules (CMA).C’est pour répondre à cette préoccupation que la présente étude s’est fixée pour but d’évaluer le potentiel mycorhizien des champignons indigènes des sols pollués de la décharge du Parc M’Ploussoué de Bonoua grâce à un test biologique avec Zea mays L. et Acacia mangium, comme des plantes pièges des microorganismes indigènes. Ainsi, après 45 jours de culture, le potentiel mycorhizien a été déterminé à partir de l’extraction desspores par tamisage humide, de la coloration des racines au bleu de trypan et du dénombrement des souches fongiques. L’analyse macroscopique des spores et des souches fongiques a révélé la présence du genre Glomus sp. (90%) appartenant à l’ordre des Glomales et également d’espèces peu spécifiques à acacia comme Aspergillus sp., Fusarium sp., Trichoderma sp. et Penicillium sp. L’examen microscopique des racines de Zea mays et de Acacia mangium a indiqué une fréquence (80 to 90%), une intensité (15 to 40%) de mycorrhization et un nombre d’arbuscules (87,5%) et de vésicules (12 to 100%) très importants sur le sol pollué. La formation des types de structures endomycorhiziens (vésicules et arbuscules) suggère la présence de champignons endomycorhiziens vesiculo-arbusculaires (CMVA) symbiotiques capables d’initier une symbiose et de favoriser un meilleur développement Acacia mangium malgré la pollution. Au su de ces résultats, les spores des CMVA de ce site pourraient être utilisées dans la remédiation du site.   English title: Assessment of the Mycorrhizal Potential of Polluted Soils of M’Ploussoue Landfill in Bonoua, Côte D’Ivoire The accumulation of toxic substances such as metallic trace elements (TME) in landfill soils of the M'Ploussoue site in Bonoua could affect microorganisms proliferation specifically the sporulation and germination of spores of Arbuscular Mycorrhizal Fungi (AMF). To address this concern, this study was to assess the mycorrhizal fungi indigenous potential of polluted soils of M’Ploussoue landfill in Bonoua by a biological test with Zea mays L. and Acacia mangium Wild, as an host plants in trap culture of indigenous mycorrhizal fungi. After 45 days of culture, the mycorrhizal potential was determined through the extraction of the spores by soil wet sieving, the roots clearing with trypan blue and the count of fungal strains. The macroscopic analyzis of the spore and fungi strains revealed the majoritory presence of Glomus spp. (90%) belonging to the Glomal orderand also the presence of nonspecific fungi especies to acacia as Aspergillus spp., Fusarium spp., Trichoderma spp. and Penicillium spp. The microscopic examination of Zea mays and Acacia mangium roots indicated frequency (80 to 90%), intensity (15 to 40%) and arbuscule contents (87.5%) and vesicles (12 to 100%) are very important in polluted soil. The formation of typical endomycorrhizal structures (vesicles and arbuscules) suggests the presence of symbiotic vesiculo-arbuscular endomycorrhizal fungi (VAMF) able to promote better Acacia mangium development despite soil pollution. Based on these results, the spores of VAFM fungi from this site could be used in the remediation of the site