Xanthomonas Wilt of banana drives changes in land-use and ecosystem services across Infected landscapes

Changes in land-use have been observed in banana-based systems in the African Great Lakes region affected by Xanthomonas wilt disease (XW) of banana. Through focus group discussions (FGDs) and the 4-cell method (to map the area under production and the number of households involved), changes in land-use were assessed in 13 XW-affected landscapes/villages along a 230 km transect from Masisi (where XW arrived in 2001) to Bukavu (XW arrived around 2014) in the Eastern Democratic Republic of Congo. Farmers’ perceptions on the sustainability of new land uses were also documented. Soil nutrient content and erosion levels were measured for five major land-use options/trajectories on 147 fields across 55 farms in three landscapes along the transect. From banana being ranked the most important crop (92% of landscapes) before XW outbreaks, its importance had declined, with it grown on smaller farms by most households in 36% of the landscapes, while in 64% of cases by few households on smaller plots. Farmers uprooted entire banana mats or fields, expanding land under other crops. Species richness did not change at landscape level, although 21 crops were introduced at farm level. Banana is, however, still perceived as more sustainable due to its multi-functional roles. Soils under banana had better chemical attributes, while high erosion levels (Mg ha−1 year−1) occurred under cassava (1.7–148.9) compared with banana (0.3–10.7) and trees (0.3–5.9). The shifts from banana could thus affect supply of key services and sustainability of the farming systems. This study offers a good basis for interventions in XW-affected landscapes

Banana pest risk assessment along banana trade axes running from low to high altitude sites, in the Eastern DR Congo and in Burundi

Pests and diseases greatly contribute to the decline in banana yields, food and income insecurity in the Great Lakes region of Africa. Understanding people’s role in pest and disease spread at landscape level is crucial for effective pest and disease management. To determine this, focus group discussions (FGDs) targeting 10 experienced farmers (50% female and 50% male) were conducted in 27 villages along four banana trade routes in western Burundi and eastern DR Congo. FGDs determined the presence and risk of spread of key banana pests and diseases via the movement of banana bunches, planting material and other products, labourers, traders and farm tools. Black leaf streak (BLS), Fusarium wilt and banana bunchy top disease (BBTD) were reported to have been in the landscape for over 40 years while Xanthomonas wilt (XW) was a more recent introduction (1-7 years). BBTD, XW and weevils were the most prevalent constraints. BBTD was observed at previously unsuitable high-altitude zones, which should be a cause of concern, especially with the current risk of climate change. Climate change, and linked temperature increases, could also worsen the prevalence of XW, weevils, nematodes and BLS. Movement of farming tools by labourers and traders, of planting material/suckers and banana bunches emerged as the most common human practices potentially responsible for the spread and/or build-up of banana pests/diseases. Strengthening farmer’s knowledge and institutional capacities of actors on these different modes of disease spread in banana value chains in the region is recommended

Sensitivity and tolerance of different annual crops to different levels of banana shade and dry season weather

Intercropping in small-holder production systems in East and Central Africa is very common and offers potential for significant yield and environmental benefits. However, the reduced light availability under banana canopies constrains the success of the intercrop in banana systems. Determining a balance between the optimal spacing/densities of banana plants with optimized intercrop selection based on their sensitivity and tolerance to shade is imperative. This study, through extensive field experiments performed in South Kivu, DR Congo investigated the resilience of a wide range of food and forage crops to varying banana shade levels. The same crop species grown as monocrops served as controls. Quantitative yield assessments showed yam, sweet potato, ginger and forage grasses to have a good potential to grow under moderately dense to dense banana fields. Taro, soybean, mucuna, chili, eggplant, and Crotalaria sp. performed well in sparsely spaced banana fields with moderate shading. Cassava and soybean showed limited tolerance to shade. Intercropping in banana systems is also generally confined to the rainy seasons due to the high sensitivity of most annual intercrops to long dry weather in the dry season months. We also thus assessed the sensitivity of chickpea and mucuna to the long dry weather of the dry seasons and found them to have great potential for extending farming production into the dry season. Overall, we show that careful selection and allocation of crops with varying sensitivity to various banana shade levels and dry season weather can potentially increase whole field productivity

Innovative agroecological practices can restore degraded farmlands and revive crop yields

Land degradation is a major obstacle to agricultural development in Africa, where it’s accentuated by poor agricultural practices and climate change effects. Restoration of degraded lands is crucial to prevent incursions into virgin and marginal lands. A field experiment was carried out over a four-year period on two degraded sites, to assess and compare the effect of the common practices of: (i) burning crop residues and weeds by resource-poor farmers (T1) and (ii) burning crop residues and weeds followed with application of manure and/or NPK as external inputs (T2) by resource-endowed farmers with (iii) an innovative agroecological package (T3) on soil physical, chemical and biological attributes, and crop yields. T3 consisted of crop rotation and/ intercropping with Mucuna pruriens cover crop, grasses (Pennisetum purpureum and Setaria sphacelate) and shrubs (Calliandra calothyrsus, and Leucaena diversifolia), and the application of manure and NPK. A randomized complete block design with 8 and 10 blocks, with each package appearing once in each block, was used respectively, at Mulungu and Mushinga. The agroecological package significantly improved soil and plant parameters compared to the common practices at both sites. The average plot- level aboveground biomass was significantly lower (p < 0.001) in T1 (11.3–17.4 t/ha) and T2 (10.1–21.9) than in T3 (39.9–60.4 t/ha). Similar trends were observed for bean and maize grain and banana bunch yields. When T1 is compared to T3, mean yields increased 2.6 times (848 kg/ha against 327 kg/ha), 2.8 times (2,201 kg/ha against 792 kg/ha) and 1.5 times (7.4 t/ha against 5.0 t/ha) for bean grains, maize grain, and banana bunches, respectively. Improvements were also observed for soil physical, biological, and chemical properties. A decrease in soil temperature; and increases in soil porosity, earthworm density/m2 (1,932 against 0), nodules/bean plant (28 against 21) and root length density (65 against 15.5cm) were observed in T3. T3 (compared to T1), had a decrease in acidity and Al3+; an increase in soil organic matter, K+, Ca+, and aboveground carbon stock (26.5 t/ha against 5.6 t/ha). The innovative agroecological package is thus an approach that can be used to effectively restore degraded and abandoned farmlan

Évaluation agronomique des variétés de haricot volubile riches en micronutriments dans un système intégré d’Agroforesterie sur deux sols contrastés à l’Est de la RD Congo

Objectif: L’objectif de cette étude était d’évaluer différentes variétés de haricots riches en fer et zinc dans un système intégré de type «jachère-herbage agro-forestière».Méthodologie et résultats: Le dispositif expérimental était le split plot avec comme parcelles principales le type de jachère-herbage agro-forestière, elles étaient subdivisées en quatre sous parcelles secondaires chacune correspondant à une variété de haricot. Les parcelles étaient au total onze et constituaient les différents traitements : T00 (témoin : 0 herbage-arbres, 0 NPK et 0 Fumier) ; T0 (NPK+Fumier), T1 à T9 issus de la combinaison herbes x arbres+NPK et fumier. Les 11 parcelles principales ont constitué un bloc répété cinq fois par site. Le fumier (20 t MS/ha) et les micros doses d'engrais NPK (50 kg.ha-1) étaient appliqués. Des différences ont été observées entre les traitements et les deux sites. Le traitement NPK+Fumier (T0) a donné les rendements en graines de haricots et les teneurs en zinc et en fer dans les graines de haricots les plus élevés dans les deux sites, dans le site avec sol fertile le rendement était de 1144,2 kg.ha-1 de graines et dans le site avec sol pauvre de 260, 6kg.ha-1 de graines). Les traitements T00 et NPK + Fumier+ jachère-herbage agro-forestière ont donné des rendements les plus bas (12,2 et 4,7 kg.ha-1) respectivement dans les sols pauvre et fertile. Les scores de maladies étaient bas, les variétés ont affiché une réaction intermédiaire.Conclusion et application de résultats: L’application de la microdose d’engrais et la jachère-herbage agroforestière ont augmenté le rendement en graines et la teneur en micronutriments dans les graines de haricots. En plus, cet effet était plus prononcé sur sol pauvre que sur sol fertile. L’application de microdoses d’engrais minéral et organique est l’un d'importantes pratiques pour améliorer le rendement de haricots dans le sol pauvre de Mushinga.Mots clés: Arbustes, fertilité du sol, graminées, légumineuses, haricots biofortifiés, rendementEnglish AbstractEnglish Title: Agronomic evaluation of different climbing beans varieties rich in micronutrient in an integrated Agroforestry systems in two contrasting soils in south Kivu, Eastern DR CongoObjective: The objective of this study was to evaluate different varieties of climbing beans (Phaseolus vulgaris L.) rich in iron and zinc in an integrated agroforestry system.Methodology and Results: The experiments were established in two sites using a split-plot design, with the main plot treatments consisting of agroforestry-fallow types. These plots were 11 in total: T00 (control: 0 grasses, trees, NPK and manure); T0 (NPK+manure), T1 to T9 from the combination grass-trees+NPK and manure and were repeated five times per site. They were subdivided into 4 subplots, each corresponding to one variety of beans. Manure (20 t DM/ha) and micro doses of NPK fertilizer (50 kg ha-1) were applied. Differences were observed between treatment and between sites. The treatment with NPK+manure (T0) gave the highest grains yields and content in zinc and iron in the grain beans in the two sites, 1144.2 kg ha-1 for site with fertile soil and 260.6 kg ha-1 in poor soil.The T00 treatments and NPK+manure+agroforestry fallow grassland gave the lowest bean grain yields (12.2 and 4.7 kg ha-1) respectively in the poor and fertile soils. Disease scores were low, varieties showed intermediate reaction.Conclusion and application of results: Bean grain yield and micronutrient content in the grain beans were enhanced with application of microdose of fertilizers and agroforestry-fallow grassland. In addition, this effect was more pronounced on poor soil than on fertile soil. The application of microdose of mineral and organic fertilizer is one of the important practices for improving bean yield in the poor soil of Mushinga.Keywords: Biofortified beans, grasses, legumes, shrubs, soil fertility, yiel

Comparing effectiveness, cost- and time-efficiency of control options for Xanthomonas wilt of banana under Rwandan agro-ecological conditions

Xanthomonas wilt of banana (XW) is a major disease affecting banana throughout East and Central Africa (ECA). Initial control was through complete diseased mat uprooting (CDMU), which had limited adoption due to high labour demands and cost. Further research demonstrated single diseased stem removal (SDSR) was an effective, less labour intensive and less costly alternative to CDMU. A comparative assessment of the two control practices was needed to foster uptake by policy makers, especially in countries like Rwanda where SDSR had not been tested or scaled up. To test SDSR in Rwanda, a study was conducted in farmers’ fields comparing the effectiveness, labour cost and time demands of CDMU and SDSR. SDSR was equally effective as CDMU for XW control, with initial XW incidences of 3.0 to 9.4% being reduced to <0.5% within 3 months of using either method. The major benefit of SDSR lies in its significantly lower resource requirements. The total time needed for applying SDSR on a single plant was 88% less, averaging 4.3 min (standard deviation, sd = 0.3) compared to 36.5 min (sd = 4.5) for CDMU on a complete mat. Accordingly, the cost of labour was significantly lower for SDSR. The main cost of CDMU (78% of total cost) arose from the need to replant with healthy banana plantlets. The total cost of SDSR (26 Rwandan Francs [Frw], sd = 2) was 96% lower than that for CDMU (619 Frw, sd = 27). Hence, the incentive to use SDSR for managing XW is very high. These findings will boost SDSR adoption by both policy makers and farmers in ECA

The integration of shade-sensitive annual crops in Musa spp. plantations in South Kivu, Democratic Republic of Congo

Small-holder banana fields are often intercropped with various annual crops to optimize land-use in East and Central Africa, a practice severely constrained by light availability under the banana canopy. Light availability is not a major constraint in newly established banana fields, giving a window of opportunity to target light-demanding annual crops before shifting to more shadetolerant crops. This study investigated the performance of climbing and bush beans and the vegetable amaranth in banana fields with varying shade levels across three sites in the South Kivu province, DR Congo. These crops were selected for their highly nutritious and good market value and the added benefit of nitrogen fixation for the legumes. We show that both grain legumes and vegetable amaranth can achieve reasonable yields during a first annual cropping season in newly established banana fields, irrespective of the plant density. Declines in yield occurred during a second cropping season in more densely spaced banana fields (2 2 m and 2 3 m). A greater decline occurred in amaranth and its cultivation should be limited to the first annual cropping season or to less dense banana fields. The legumes could be extended to a second cropping season with reasonable yield. Significant variability in amaranth and legumes performance was observed across sites, with rapid yield declines occurring under more fertile soil conditions due to fast banana growth/canopy formation and under more vigorous cultivars. The choice of banana spacing will need to be tailored to the banana cultivar, soil conditions and the farmers’ objectives