Effet des champignons mycorhiziens Arbusculaires sur le phosphore des sols tropicaux et implication dans la biosynthèse du caroténoïde du manioc

Open Access Journal; Published online: 31 March 2019Objectifs : Evaluer du point de vue agronomique les avantages attribués aux champignons mycorhiziens arbusculaires (CMA) par rapport aux sols des zones des forêts humides et vérifier le rôle que le phosphore mobilisé par ces champignons jouerait dans la biosynthèse du caroténoïde. Méthodologie et résultats : Deux variétés de manioc étaient soumises aux inoculations apportées seules ou combinées aux autres fertilisants. Les analyses de sol effectuées en amont et en aval du manioc ont permis de constater des changements significatifs en ce qui concerne l'acidité mesurée à 4,6 de pH avant le manioc et 6,3 après inoculation des CMA. Des changements sont également observés sur la structure du sol où on a observé des modifications partant de la structure particulaire au départ à une structure grumeleuse après application de fumier combiné aux inoculations des CMA. Ces inoculations ont fait augmenter la teneur du phosphore dans le sol à 7,5 %, l’azote à 4 % et le carbone à 13%. Le rendement du manioc a donné des moyennes de 55 t ha-1 de racines sous inoculation contre 21 t ha-1 de racines lorsque le sol n’était pas traité. On a noté des modifications significatives du caroténoïde total dans la racine de manioc lorsque le sol était inoculé et était plus pourvu en phosphore. Conclusions et champs d’application des résultats : les champignons mycorhiziens sont présents dans les sols tropicaux des forêts humides et peuvent être multipliés sous le sorgho. Lorsqu’ils sont inoculés en champ de manioc, ils permettent à la fois des accroissements de rendement du manioc, la disponibilisation du phosphore autrefois complexé par les cations acides du sol et l’accélération de la biosynthèse du caroténoïde total du manioc jaune. La possibilité de réaliser des multiplications en cascade de ces champignons et leur conditionnement sur des substrats stériles permettra de fabriquer des inocula locaux qui pourront être utilisés comme fertilisant biologique en lieu et place des fertilisants minéraux conventionnels. Objectives: To evaluate agronomically the advantages attributed to Arbuscular Mycorrhizal Fungi (AMF) compared to soils in humid forest zones and verify the role that phosphorus mobilized by these fungi would play in the biosynthesis of carotenoid of yellow cassava. Methodology and results: Two varieties of cassava were inoculated alone or in combination with other fertilizers. Soil tests carried out before cassava cultivation and after harvest showed significant changes in acidity measured at 4.6 pH before cassava and 6.3 after inoculation with AMF. Changes were also observed in soil grain size with 71% sand initially and 65.5% after application of manure combined with inoculations (LSD.05 = 2.7%). These inoculations increased the soil phosphorus content to 7.5%, nitrogen to 4% and carbon to 13%. Cassava yield averaged 55 t ha-1 under inoculation versus 21 t ha-1 when the soil was untreated. Significant changes in total carotenoid in the cassava root were noted when the soil was inoculated and had a higher phosphorus content. Conclusions and application findings: Mycorrhizal fungi are present in tropical soils of moist forests and can be propagated under sorghum. When inoculated in the cassava field, they allow both increases in cassava yield, the availability of phosphorus once complexed by acidic soil cations and the acceleration of the total carotenoid biosynthesis of yellow cassava. The possibility of performing cascade multiplications of these fungi and their conditioning on sterile substrates will make local inocula that can be used as biological fertilizer instead of conventional mineral fertilizers

Determination of optimal sowing periods for short and medium cycle rice varieties in Yangambi

Open Access Article; Open Access ArticleRice is the staple food for more than 2.5 billion people in developing countries with very high annual consumption exceeding in some countries 100 kg per capita. The African continent has become one of the main import poles for rice with about one quarter (1/4) of world imports because of its low production, which barely reaches 1.5% of world production. Following the agricultural calendar and in accordance with studies conducted at INERA - Yangambi on the probable periods of sowing rice in Yangambi, it appears that rice can be sown from March 15 to October 15 during the year and mainly in the wetlands of the tropics. A variety of rice, so that it can express its genetic potential, must benefit from the maximum of water and light so that one can hope for optimal yields. It is in this context that this study was conducted and with the objective of contributing to the search for the appropriate sowing dates for short and medium cycle rice varieties that would help farmers maximize their income. Depending on each sowing date, observations were made on the number of panicles per m², the number of grains per panicle, the length of the panicle, the weight of a thousand grains and the yield. The results showed that optimal planting times for rainfed rice are good when short-cycle and when rice is planted from 16 May and from 15 June for medium-cycle rice varieties. Some short and / or medium cycle varieties are favorable for sowing dates around June 29th. The benefit from this relatively late sowing of June is alluding to bird damage and so the varieties that adapt to these dates have been identified. Le riz représente la base de l'alimentation de plus de 2,5 milliards de personnes dans les pays en voie de développement avec des consommations annuelles très importantes dépassant dans certains pays les 100 kg/habitant. Le continent africain est devenu l'un des principaux pôles d'importation de riz avec environ le quart (1/4) des importations mondiales à cause de sa faible production qui atteint à peine 1,5% de la production mondiale. Suivant le calendrier agricole et conformément aux études entreprises à l’INERA – Yangambi sur les périodes probables de semis du riz à Yangambi, il ressort que le riz peut être semé du 15 Mars au 15 Octobre au courant de l’année et principalement dans les régions humides des tropiques. Une variété de riz, pour qu’elle puisse exprimer son potentiel génétique, doit bénéficier du maximum de l’eau et de la lumière pour qu’on puisse espérer des rendements optima. C’est dans ce cadre que cette étude a été menée et avec pour objectif de contribuer à la recherche des dates de semis convenables des variétés de riz, à cycles court et moyen, qui aideraient les agriculteurs à maximiser leur revenu. En fonction de chaque date de semis, les observations ont porté sur le nombre de panicules par m², le nombre de grains par panicule, la longueur de la panicule, le poids de mille grains et le rendement. Les résultats obtenus ont montré que les périodes optimales de semis du riz pluvial sont bonnes lorsque le riz à cycle court est semé à partir du 16 mai et à partir du 15 juin pour les variétés de riz à cycle moyen. Certaines variétés à cycle court et/ou moyen sont favorables aux dates de semis oscillant autour du 29 juin. L’avantage qui découle de ce semis relativement tardif du mois de juin fait allusion aux dégâts des oiseaux et ainsi, les variétés qui s’adaptent à ces dates ont été identifiées

Cassava yield loss in farmer fields was mainly caused by low soil fertility and suboptimal management practices in two provinces of the Democratic Republic of Congo

Article purchasedA better understanding of the factors that contribute to low cassava yields in farmers’ fields is required to guide the formulation of cassava intensification programs. Using a boundary line approach, we analysed the contribution of soil fertility, pest and disease infestation and farmers’ cultivation practices to the cassava yield gap in Kongo Central (KC) and Tshopo (TSH) provinces of the Democratic Republic of Congo. Data were obtained by monitoring 42 and 37 farmer-managed cassava fields during two cropping cycles in KC and one cropping cycle in TSH, respectively. Each field was visited three times over the cassava growing period for the observations. Logistic model was fitted against the observed maximum cassava root yields and used to calculate the achievable yield per field and for individual factor. At field level, the factor that led to the lowest achievable yield (Yup(i)1) was considered as the dominant yield constraint. Cassava yield loss per field was expressed as the increase in the maximal root yield observed per province (Yatt- attainable yield) compared to Yup(i)1. Yatt was 21 and 24 t ha−1 in TSH and KC, respectively. With the cassava varieties that farmers are growing in the study areas, pests and diseases played a sparse role in the yield losses. Cassava mosaic was the only visible disease we observed and it was the dominant yield constraint in 3% and 12% of the fields in KC and TSH, respectively. The frequent yield constraints were suboptimal field management and low soil fertility. Cultivation practices and soil parameters led to Yup(i)1 in 47% and 50% of the fields in KC, and in 47% and 41% of those in TSH, respectively. Individual soil parameters were the yield constraint in few fields, suggesting that large-scale programs in terms of lime application or recommendation of the blanket fertilisers would result in sparse efficacy. In KC, yield losses caused by low soil fertility averaged 6.2 t ha−1 and were higher than those caused by suboptimal field management (5.5 t ha−1); almost nil for cassava mosaic disease (CMD). In TSH, yield losses caused by low soil fertility (4.5 t ha−1) were lower than those caused by suboptimal field management (6.5 t ha−1) and CMD (6.1 t ha−1). Irrespective of the constraint type, yield loss per field was up to 48% and 64% of the Yatt in KC and TSH, respectively. Scenario analysis indicated that the yield losses would remain at about two third of these levels while the dominant constraint was only overcome. We concluded that integrated and site-specific management practices are needed to close the cassava yield gap and maximize the efficacy of cassava intensification programs

Enhancing yield and profitability of cassava in the savannah and forest zones of Democratic Republic of Congo through intercropping with groundnut

Objective: This study was conducted to simulate intercropping of cassava and groundnut as practiced by farmers in the savannah and forest zones of Democratic Republic of Congo (DRC). It aims to (i) evaluate the intercropping of two most cultivated food crops (Cassava and Groundnut) under conditions of marginal soils of the tropics and (ii) propose alternatives to farmers that can enhance productivity.Methods and results: At each location, a split plot design was used with Cassava branching habit (branching type –Erect, Branched and medium habit) as the main plot and System that is association with groundnut (intercrop) or without (monocrop) as the subplot. A combined model with sites was fitted using the Mixed Model with SAS v9.4. The results suggest that in the equatorial and savannah zones the performance of both crops was influenced by the type of branching of cassava stem used in the intercrop with erect types yielding more. Non-significant differences were observed in groundnut yield for all effects. The calculation of Land Equivalent Ratio (LER) and economic analyzes drawn from the marginal rate of return (MRR) clearly showed an advantage of intercropping over the sole cropping system.Conclusion and application: The practice of intercropping groundnut and cassava is advantageous. However, the choice of the variety of cassava based on the branching habit influences the growth and productivity of groundnuts. Optimal production of the two crops and profit was attained where the cassava variety has erect habit. Local varieties with medium habit were generally unhealthy, performed poorly and are therefore not recommended in intercropping systems.Keywords: Productivity; Land Equivalent Ratio; cropping systems; marginal rate of retur

Effect of Tillage and the Position of Cuttings on Cassava Root and Leaf Yields in the Savanna and Forest Fallow Zones of the Democratic Republic of Congo

In Democratic Republic of Congo (DRC), cassava covers more than half of the area under cultivation and is permanently consumed by more than 70% of the population for its roots and about 80% for its leaves, which are one of the main vegetables in the country. National cassava production suffered a setback in the early 1990s and an annual arithmetic reduction of the cassava production, from this period to the start of a program on the rehabilitation of the crop. The main objective of the program was to develop varieties with high dry yield and resistant to cassava diseases and pests mainly the cassava mosaic disease (CMD) because the latter was identified as the major cause for the low production recorded. As and when the program gained momentum, many other factors appeared to have important role for the effective recovery of cassava production. Soil fertility management and cultural practices are amongst them. This study was conducted in this context in two different agro-ecological zones (Litoy in Kisangani hinterlands in forest zone and Plateau de Bateke at the East of Kinshasa in savannah zone). The soil of Litoy is heavier than the one of Plateau des Bateke whose sand content is higher than 90%. The method of land preparation influenced the production of cassava roots and leaves in the grassy fallows of the forested areas of the Kisangani region. A 45% increase of the root yield was obtained in this area when the soil was plowed. An stable yield of 14 t/ha was obtained in the Bateke plateau savannah regardless of the land preparation method. The position/orientation of cuttings at planting did not indicate significant statistical differences. However, higher gross profit margins were obtained on plowed land with US$2500/ha compared to US$1500/ha on no tilled land

Storage root yield response to leaf harvest of improved and local cassava varieties in DR Congo

Published online: 07 Aug 2020Although cassava is usually grown for its starchy roots, cassava leaves are an important vegetable and protein source in sub-Saharan countries. Eleven cassava mosaic disease (CMD) tolerant and two susceptible varieties were planted in six trials; leaves were harvested at 4, 8 and 11 months after planting (MAP) and storage roots were harvested at 12 MAP. Edible leaf and storage root dry matter yields were strongly affected by variety and interacted with location. Edible leaf yields ranged from 209 to 435 kg ha−1 DM among varieties. Storage root yields ranged from 2540 to 9250 kg ha−1 DM among locations and from 2470 to 7550 kg ha−1 among varieties. Leaf harvest caused 15.8% storage root yield loss. Susceptible varieties produced lowest edible leaf (209 kg ha−1) and storage root (2530 kg ha−1) yields in all locations. Improved varieties suffered storage root yield reductions of 5–25.8%, equivalent to 400–1550 kg ha−1. Edible leaf yield and storage root yield were not correlated. Variety TME419 produced the highest average storage root yields in 3 of 6 locations. The three best leaf producing varieties were not among the best storage root producers, indicating an incompatibility of the two production objectives

Development des moyens de lutte contre le « Shimbu », cas de la culture du manioc au kasai oriental/RDC: Revue et contribution sur les moyens de lutte contre le complexe parasitaire shimbu

L'interaction des plusieurs contraintes, à savoir les maladies et ravageurs du manioc, les pratiques culturales inadéquates, la faible fertilité des sols, etc. contribuent à la baisse de la productivité du manioc. Il a été constaté à Luputa et Ngandajika que les champs des agriculteurs y compris les champs de manioc sont souvent infestés par un complexe maladie/ravageur localement appelée « shimbu ». Cette revue a pour objectif l'inventaire des connaissances et des différents moyens de lutte existants contre le « shimbu » afin de mieux orienter les nouvelles recherches et formuler certaines recommandations auprès des agriculteurs. Une enquête auprès des agriculteurs et l'inventaire de la littérature sur le « shimbu » ont été réalisés. La visite sur terrain a permis d'apprécier la perception du complexe « shimbu » par les agriculteurs, visualiser les symptômes ainsi que formuler quelques moyens de lutte. Il en découle que (i) « shimbu » qui signifie « déraciner en Ciluba» est un complexe des petits insectes ailés, vivant dans le sol, se reproduisant à partir des oeufs et qui, en association avec les fourmis/ champignons, s'attaquent aux plantes à partir des racines » ; (ii) les symptômes sont entre autres : l'apparition des insectes et des petits oeufs lors du labour ; le faible taux de reprise après plantation ; la fanaison des plantes attaquées qui s'arrachent facilement ; (iii) les principaux moyens de lutte sont : bon choix du terrain, labour profond, plantation sur billons/buttes, enfouissement et semis des plantes odorantes, épandage de la cendre. La recherche sur le « shimbu » dans la province du Kasaï date des années 1950 par l'INEAC et le nom de « shimbu » était associé aux dégâts causés par l'association d'un coccide, voisin du genre Gueriniella, de fourmis, appartenant aux genres Camponotus et Crematogaster, et d'un champignon, Macrophoma phaseoli. De 1950 à 1958, l'INEAC a menée des essais essentiellement sur la lutte à base des insecticides chimiques qui devraient être économiques, efficaces contre le « shimbu » et d'utilisation aisée en milieu rural. Toutefois, les résultats obtenus ne garantissaient pas forcément la rentabilité et outre le fait que les insecticides représentent un danger pour la santé et l'environnement, ils ne sont pas toujours à la portée des paysans. Cependant, certaines pratiques culturales (labour profond, plantation précoces, etc.), bien appliquées et de façon préventive, semblent être des moyens efficace de lutte contre le « shimbu ».Par conséquent, nous suggérons : (i) un approfondissement de la connaissance du complexe « shimbu » par des analyses appropriées au laboratoire et (ii) l'initiation des essais sur les pratiques culturales, les plantes insecticides ainsi que les variétés performantes

On the origin of the royal Kongo title ngangula

This article offers an in-depth historical-comparative linguistic account of the origin and etymology of ngangula. This term is not only a widespread blacksmith term in the Lower Congo region, but also a traditional royal Kongo title attesting to the importance of the blacksmith metaphor in Kongo political ideology. Popular etymology has it that ngangula is related to nganga, reconstructed in Proto-Bantu as *-gàngà and commonly translated as ‘ medicine-man’. It is argued here that this widely held belief does not stand up to scrutiny. The term ngangula is shown to be derived from the common Bantu verb * pàngʊd-meaning ‘ to cut ; to separate’. Thanks to a distinctive diachronic sound change, it is even possible to locate quite precisely the term’s origin within the Kikongo dialect continuum. Its provenance gives new credibility to an earlier but discarded hypothesis situating the origins of the Kongo kingdom in the eastern part of the Lower Congo, somewhere in‑between the Inkisi and Kwango Rivers.Cet article offre une étude approfondie en linguistique historico-comparative sur l’origine et l’étymologie de ngangula. Ce terme est non seulement répandu dans la région du Bas-Congo pour forgeron, mais c’est aussi un titre royal traditionnel kongo qui atteste de l’importance de la métaphore du forgeron dans l’idéologie politique kongo. L’étymologie populaire veut que le terme ngangula soit lié à nganga, reconstruit *-gàngà en proto-bantu et généralement traduit par ‘ guérisseur’. Nous montrons ici que cette croyance largement partagée ne résiste pas à un examen approfondi. Nous montrons que le terme ngangula dérive plutôt du verbe *-pàngʊd- bien attesté en bantu et signifiant ‘ couper, séparer’. À partir de l’évidence diachronique d’un changement phonétique distinctif, nous pouvons même situer assez précisément l’origine du terme au sein du continuum dialectal kikongo. Sa source crédibilise à nouveau une hypothèse ancienne mais rejetée qui situait les origines du royaume kongo dans la partie orientale du Bas-Congo, quelque part entre les rivières Inkisi et Kwango.Bostoen Koen A. G., Ndonda Tshiyayi Odjas, De Schryver Gilles-Maurice. On the origin of the royal Kongo title ngangula. In: Africana Linguistica 19, 2013. pp. 53-83

Miscellanea Herpetologica Gabonica XVI

We present new Gabonese locality records, ecological and morphological data or unpublished material for Kinixys erosa (Testudinidae), Trachylepis albilabris (Scincidae), Calabaria reinhardtii (Boidae), Dasypeltis fasciata, Hapsidophrys smaragdinus, Philothamnus carinatus, P. heterodermus and P. nitidus nitidus, Thrasops flavigularis,Toxicodryas blandingii and T. pulverulenta (Colubridae), Dendroaspis jamesoni jamesoni,Naja melanoleuca (Elapidae), Mehelya poensis, Polemon collaris (Lamprophiidae), Natriciteres fuliginoides (Natricidae), Python sebae (Pythonidae), Bitis gabonica and Causus maculatus (Viperidae). One snake species is newly recorded from Loango National Park, and three from Estuaire Province

Influence de differents types de port de manioc de la variete << Kindisa >> sur la teneur en beta carotene

Open Access ArticleCassava is the most consumed speculation in Yangambi, may help to address vitamin A deficiency problems. The study aimed to assess the yield, beta-carotene content and dry matter content of a variety of cassava. biofortified in beta-carotene (Kidisa) by comparing its three types of habit (branched, moderately branched and erect habit) under the agro-ecological conditions of Yangambi. The experimental device consisted of linear plots of 25m X 50m. The analysis of the mean was carried out, the root yield calculated then the beta-carotene content estimated by port and the dry matter. The results showed that the branched, semi-branched and erect ports, respectively provide beta-carotene, dry matter and yields of tuberous roots of 6.9 μg / g; 29.4%; 40.66 t / ha for branched crops, 6.2 μg / g; 31.1%; 37.41 t / ha for semi-branched and 5.7 μg / g; 34.7%; 30.88% t / ha for the upright. Despite its poor performance, the latter deserves popularization in a peasant environment using a participatory approach by decision-makers