Suchergebnisse

Harvesting young cassava leaves as a vegetable is a common practice in the Democratic Republic of Congo (DR Congo). However, information on its effects on growth and yield of cassava is scarce. Multi-locational trials were conducted on farmers' fields in the province of South Kivu, DR Congo, during two consecutive years to investigate the effects of harvesting frequency of 3 young leaves (no leaf harvesting (NoH); leaf harvesting at 4 week intervals (4-WI) or 2 week intervals (2-WI), starting 4 months after planting) and fertilizer (with or without NPK application) on the growth and yields of cassava, comparable to common practice by farmers in the area, based on a preceding household survey. Overall, harvesting of leaves did not result in significant effects on both height and stem diameter compared with the unharvested treatment. However, collection of leaves at 2-WI significantly (P < 0.05) decreased both height and stem diameter, and resulted in significant (P < 0.1) reduction of stem yields of 20.9% (4.0 t ha‐1) relative to leaf harvesting at 4-WI but only in the second year. Average total biomass and storage root yields in the control treatment were 35.8 and 23.5 t ha−1, respectively and were not significantly affected by leaf harvesting. Application of NPK fertilizer resulted in significant (P < 0.05) increases of both height and stem diameter over time, independent of the frequency of leaf harvesting. Mineral fertilizer significantly (P < 0.05) increased the overall total, storage root and stem yields by 28.3% (9.5 t ha−1), 19.9% (4.5 t ha−1) and 45.1% (5.0 t ha−1), respectively regardless of the frequency of leaf harvesting. This study indicates that harvesting of young leaves results in small or negligible effects on cassava growth and yields compared to the mineral fertilizers which increase both cassava growth and yields in the conditions of our study.

Banana-bean intercropping systems are used by many small-scale farmers in eastern Democratic Republic of Congo to maximize land use and intensify crop production. A study was conducted at the INERA Mulungu research station to determine the effect of banana leaf pruning on banana (Musa spp.) and bean (Phaseolus vulgaris, Fabaceae) yield. The East African highland cooking banana 'Barhabesha' was established in April 2007 at a spacing of 2 by 3 meters. The treatments consisted of different levels of banana leaf canopy coverage (5 leaves [5L] and all leaves [ALL]) and leguminous crop varieties (the bush bean 'Ngwaku Ngwaku' and the climbing bean 'AND10') which were planted in the banana plot. Bean yields were assessed during 4 cropping seasons (2008B, 2009A, 2009B and 2010A). Banana leaf pruning did not have a significant effect on time from planting to bunch harvest in either legume intercropping treatment. Banana leaf pruning did not have a significant effect on banana yield (32.3 and 28.6 t/ha for ALL; 32.2 and 26.3 t/ha for 5L for climbing and bush bean intercropping respectively). The average banana bunch weight was higher in the climbing bean (ALL: 19.4 / 5L: 19.4 kg) than in the bush bean intercropped plots (ALL: 17.2 / 5L: 16.1 kg). A reduction in the number of banana leaves (i.e. from all leaves to 5 leaves) enhanced bean yield for both legume types. Under the all leaves treatment, climbing bean yield (358 kg/ha) was slightly but not significantly higher than bush bean yield (335 kg/ha). However, it was significantly higher for the 5L treatment (512 kg/ha against 362 kg/ha). Results from a gross margin analysis of banana-bean intercropping and cropping season effects are also presented. ; Directorate-General for Development Cooperation and Humanitarian Aid, Belgium ; Peer Review

Cassava intercropping is a common practice in sub-Saharan Africa. In terms of growth pattern, canopy development and nutrient demand, grain legumes are well suited for intercropping with cassava. Due to the inter-specific competition for growth resources, the relative planting time of the component crops has been considered as one of the important management practices for intercropping system productivity. Little information exists on the effect of cassava planting time on yields and economic returns of a cassava-legume intercrop. This study investigated the effect of relative planting times of cassava on yields and economic returns of a cassava-groundnut intercrop. Researcher-managed, field trials were installed in Bas-Congo Province in two consecutive seasons using four different planting times of cassava after the groundnuts. The results indicated that cassava planting time did not affect both grain and biomass yields of groundnut. When cassava was planted 3 weeks after the groundnuts, cassava storage root yields were significantly (P = 0.029) decreased by 48 to 60 % (9.3 to 11.3 t ha-1) over cassava planted at the same time as groundnut. The net revenue of cassava planted 3 weeks after the groundnut was significantly (P = 0.002) decreased by about 70 % over that of cassava planted at the same time or 2 weeks after the groundnuts. Maximum net revenue of $ 1877 ha-1 with a benefit-cost ratio of 2.42 was reported in the treatment of cassava planted at the same time. Benefit-cost ratio was favourable for the pure cassava (3.2 to 3.8) but not favourable for the pure groundnut. Cassava intercropping with groundnut had significantly (P = 0.019) lower profits than the pure cassava. The results suggest that cassava should be planted at the same time or not later than 2 weeks after the groundnuts to maximize yields and economic returns in a cassava-groundnut intercrop. ; Peer Review

Banana-legume intercropping systems are commonly practiced in the highland zones of the eastern Democratic Republic of Congo to maximize land use and intensify crop production. However, banana leaves are pruned during legume intercropping to improve sunlight penetration for the legume. On-farm experiments were conducted in South Kivu province to determine the effect of banana leaf pruning on banana (Musa sp.), bush and climbing beans (Phaseolus vulgaris L) and soybean (Glycine max L) yield. Legumes were planted in existing farmers' fields of East African highland beer banana genotype 'Nshikazi' (Musa sp., AAA-EA) during four cropping seasons covering 30 months. The experiments were established using a split-plot design, with the main plot treatments consisting of two levels of banana leaf canopy pruning (leaving only seven leaves or leaving all leaves) and the split plot treatments consisting of improved or local leguminous crop cultivars (the bush bean 'MLB49', the climbing bean 'AND10' and soybean 'SB24' planted in the banana plot. Each farmer's banana plot was a replicate). A total of 24 replicates, each of improved and local soybean, improved and local climbing bean and improved and local bush bean were planted in established farmers' fields located in four sites. Bean yields were assessed during four consecutive cropping seasons (2010B, 2011A and B, 2012A) and one cycle of banana cultivation. Banana leaf pruning did not have a significant effect on banana bunch weight or yield, but legume type affected banana fruit weight and yield in Burhale and Lurhala, which have poor soil fertility. Banana leaf pruning enhanced legume grain yield for the four seasons at all sites.

Article purchased ; A 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. ; African Development Bank ; Peer Review