Plantain hybrids for the humid forest agroecology of Central Africa – diseases and pests load, fruit yield and farmers perception

Open Access Journal; Published online: 01 Nov 2022Plantain is one of the major staples contributing to food security and income generation in West and Central Africa. Local cultivars in Cameroon are susceptible to pests and diseases causing severe losses in plantain production. This study aimed at evaluating the agronomic performance and producer’s perception of plantain hybrids in the humid forest of Cameroon. Field trials were established in a completely randomized block design with eight genotypes and three replicates. Data on pest and disease as well as farmer perception were collected over two growing cycles. These genotypes included seven improved and one local genotype (check). Improved genotypes were highly tolerant to the Black Sigatoka disease compared to local plantain. While root necrosis index was above 50% in local varieties, indices below 25% were recorded in hybrids. Weevil severity in local was higher (55.0 ± 5.2%) compared to 21.0 ± 4.6% to 28.5 ± 3.2% in improved plantains. Average bunch weight was higher for FHIA 21 with 17.9 ± 0.7 kg in the first and 19.7 ± 0.3 kg for the second cycle, while those of the local Ebang were 9.6 ± 0.5 kg and 12.8 ± 0.9 kg, respectively. FHIA 21 and CRBP 568 were the preferred varieties by farmers (68.8% and 56.3% acceptance) from an agronomic perspective. The consumers’ preferences for all the genotypes varied with types of cooking. The implications of these findings for adoption by farmers and consumers as well as for the promotion of the plantain sector in central Africa are discussed

Effect of soil chemical composition on nutrient uptake and yield of cassava (Manihot esculenta Crantz, Euphorbiaceae) in two agro-ecological zones of Cameroon

L’étude a été menée dans l’objectif d’évaluer l’influence de la composition chimique du sol sur la teneur en éléments nutritifs et le rendement du manioc dans deux zones agro-écologiques du Cameroun. L’échantillonnage s’est fait à Ekona (zone 4) et Ongot (zone 5). Une variété de manioc améliorée (8034) et deux variétés locales (Local Red et Bassa Noire) âgées de 12 mois ont été utilisées. Les résultats ont montrés que le sol d’Ekona (andosol) est significativement plus riche en éléments minéraux (azote total: 1,34% ; phosphore disponible: 15 mg.kg-1) que celui d’Ongot [(ferralsol), (azote total: 0,11% ; phosphore disponible: 4 mg.kg-1)]. La variété 8034 produit significativement plus de biomasse fraîche totale et de rendement en tubercules que les variétés locales. Elle est significativement plus riche en éléments minéraux que les variétés locales dans les deux sites. Les éléments minéraux contenus dans les feuilles de manioc sont très fortement corrélés (r2 :0,999, p<0,001) à ceux contenus dans le sol. La richesse des feuilles et des tubercules de manioc en éléments nutritifs est donc proportionnelle à celle du sol en éléments minéraux. Ce résultat préliminaire constitue une avancée dans la détermination des doses de fertilisants à recommander pour la culture du manioc au Cameroun. A study was conducted to evaluate the effect of soil chemical composition on nutrient uptake and yield of cassava in two agro-ecological zones of Cameroon. Soil and plant samples were obtained from twelve month old pure culture cassava fields at Ekona (zone 4) and Ongot village (zone 5). An improved variety (8034) and two local varieties (Local Red at Ekona and Bassa Noire at Ongot) were used. Results showed that the soil from Ekona (Andosol) was significantly higher in nutrients (total nitrogen: 1.34%; phosphorus available: 15 mg.kg-1) than the soil from Ongot [(Ferralsols), (total nitrogen: 0.11%; phosphorus available: 4 mg.kg-1)]. The improved variety accumulated significantly more total fresh biomass and root yield than the local varieties, irrespective of the site. Similarly, nutrient uptake was higher with the improved variety across the zones. A positive and highly significant correlation (r2 :0.999, p<0.001) was observed between nutrient uptake by cassava and soil nutrient availability. Thus, it may be concluded that the quantity of nutrient in the leaves and roots of cassava is proportionate to the quantity of nutrient elements in the soil. This preliminary result constitutes a solid base for the determination of an appropriate fertilizer scheme for cassava cultivation in Cameroon

Fertility management for maize cultivation in some soils of Western Kenya

Soil fertility loss in Western Kenya is exacerbated by inadequate nutrient management and causes reduced maize yields. Given the diversity of soil types, cropping seasons, and the resource endowment of farmers, the magnitude of the soil fertility decline and the effectiveness of management options to counteract this decline is likely to differ. Five organic and inorganic management options were compared with farmers’ practice regarding their effects on soil fertility attributes and nutrient balances/use efficiencies in maize on three contrasting soils of Western Kenya and over two cropping seasons. Irrespective of the season, organic amendments were more effective than mineral fertilizers in enhancing soil carbon stocks and the labile and non-labile C fractions. The largest soil C content (4.1%) and C pool (72Mgha⁻¹) were observed on the clay Nitisol after two seasons of reduced tillage, while the lowest C content (1.1%) and C pool (22Mgha⁻¹) were observed on the sandy Acrisol with conventional tillage. Total soil N content was consistently higher with mineral than with organic fertilizer use and more so on Nitisol than on Ferralsol or Acrisol. The soil N supplying capacity increased with the application of both organic and mineral fertilizers and reached 210mgkg⁻¹ after two weeks of anaerobic incubation of the mineral N-amended Acrisol. Bray-I P content reflected the P application rates and was highest (50–66mgkg⁻¹) on the Acrisol with mineral P fertilizer use and lowest (1.5mgkg⁻¹) on the Ferralsol in the unamended control treatment. Partial N and P balances were generally positive except for the mineral N-amended treatments on the Nitisol. The efficiency of applied N varied from 29 to 135kgkg⁻¹N with lowest values in the sandy Acrisol under reduced tillage. These differential responses to management options in different soil types were reflected in maize grain yields with highest cumulative yields of 4.7–9.4Mgha⁻¹a⁻¹ in the Nitisol and 1.4–7.4Mgha⁻¹a⁻¹ in the Acrisol and the Ferralsol. We may conclude that the tested technology options differentially affected soil fertility and production attributes. The extent of this response depended on the cropping season and the soil type, supporting the need for site-specific nutrient management and technology targeting

Parasitism of the whitefly Bemisia tabaci by aphelinid parasitoids on cassava across five agro-ecological zones of Cameroon

The whitefly Bemisia tabaci (Gennadius) is the vector of cassava mosaic viruses causing cassava viral diseases, which are the most important biotic constraints of cassava production in sub-Saharan Africa (SSA). Presently, B. tabaci management in cassava fields calls for the development of an integrated approach that relies on host plant resistance and biological control. Data on B. tabaci's natural enemies, particularly parasitoids, in Central Africa are limited. Field surveys were conducted from 2015 to 2017 to identify parasitoids associated with B. tabaci in 5 Cameroon agro-ecological zones. Additionally, population dynamics studies were conducted in replicated fields experiments were conducted from 2016 to 2018 to identify cassava genotypes that can best promote B. tabaci parasitism. Two parasitoids, Encarsia sophia (Girault & Dodd) and Encarsia lutea (Masi) were found parasitizing B. tabaci nymphs with higher parasitism by E. lutea compared with E. sophia. The average parasitism rate during the survey was 33.4% for E. lutea and 8.4% for E. Sophia, regardless of AEZ. The highest parasitism rates by E. lutea (48.2% and 24.2% from field trials and surveys, respectively) were observed in the Western Highlands (AEZ 3) while parasitism by E. sophia was less than 12.4%. Four cassava genotypes (I090590, I011797, I090574, and I070593) promoted higher parasitism rates of B. tabaci by E. lutea and E sophia. The contributions of the two parasitoids and their integration with cassava genotypes for the management of B. tabaci in cassava fields are discussed