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De Meyer A.,Catholic University of Leuven | Poesen J.,Catholic University of Leuven | Isabirye M.,Kawanda Agricultural Research Institute | Deckers J.,Catholic University of Leuven | Raes D.,Catholic University of Leuven
Catena | Year: 2011

In an effort to pinpoint the sources of sediment pollution in Lake Victoria, the contribution of sediment from compounds, landing sites, unpaved roads and footpaths is determined in the catchment of Nabera Bay and Kafunda Bay at the northern shore of Lake Victoria in southern Uganda. The volume of soil loss is determined in 36 compounds, 1 school and 1 landing site by comparing the original and current soil surface. The original soil surface is reconstructed using botanical and man-made datable objects. The soil loss rates are calculated by dividing the eroded soil volume by the age of the oldest datable object. Considering all compounds and landing sites in the study area, the average soil loss rate in compounds amounts to 107Mgha-1year-1 (per unit compound) and to 207Mgha-1year-1 per unit landing site. The soil loss from footpaths and unpaved roads is calculated by multiplying the total length of footpaths and unpaved roads with the average width and soil loss depth. The mean soil loss rate on footpaths is 34Mgha-1year-1 and on unpaved roads equals 35Mgha-1year-1. Compounds, landing sites, footpaths and unpaved roads occupy a small fraction of the study area (2.2%), but contribute disproportionately to the total soil loss (i.e. 85%) in the study area. It is concluded that compounds, landing sites, footpaths and unpaved roads are very significant sources of sediment pollution to Lake Victoria. This needs to be considered when designing strategies to reduce sediment production in the area. © 2010 Elsevier B.V.

Schluter U.,University of Pretoria | Schluter U.,Laval University | Benchabane M.,Laval University | Munger A.,Laval University | And 6 more authors.
Journal of Experimental Botany | Year: 2010

Protease inhibitors are a promising complement to Bt toxins for the development of insect-resistant transgenic crops, but their limited specificity against proteolytic enzymes and the ubiquity of protease-dependent processes in living organisms raise questions about their eventual non-target effects in agroecosystems. After a brief overview of the main factors driving the impacts of insect-resistant transgenic crops on non-target organisms, the possible effects of protease inhibitors are discussed from a multitrophic perspective, taking into account not only the target herbivore proteases but also the proteases of other organisms found along the trophic chain, including the plant itself. Major progress has been achieved in recent years towards the design of highly potent broad-spectrum inhibitors and the field deployment of protease inhibitor-expressing transgenic plants resistant to major herbivore pests. A thorough assessment of the current literature suggests that, whereas the non-specific inhibitory effects of recombinant protease inhibitors in plant food webs could often be negligible and their 'unintended' pleiotropic effects in planta of potential agronomic value, the innocuity of these proteins might always remain an issue to be assessed empirically, on a case-by-case basis. © 2010 The Author.

Farrow A.,Kawanda Agricultural Research Institute | Risinamhodzi K.,Chitedze Research Station | Zingore S.,Chitedze Research Station | Zingore S.,International Plant Nutrition Institute | Delve R.J.,Chitedze Research Station
Agricultural Systems | Year: 2011

Developing the rural agricultural input markets in sub-Saharan Africa can improve the current low productivity of smallholder farmers. Malawi has seen significant efforts in addressing the availability of agricultural inputs at village level in the last few years; for example, the improvement of rural agro-dealer networks. Nevertheless inputs are still difficult to obtain for many remote smallholder farmers. Spatial analysis can help in the expansion of input stockists, especially agro-dealer networks, by assessing the coverage of existing input outlets and deriving optimum locations for village-level input stockists.We address three research questions. First, what is the locational efficiency of the current village-level stockists of inputs (Citizens Network for Foreign Affairs - Rural Agricultural Market Development Trust trained network of agro dealers and public sector)? Secondly, how many village-level stockists of markets are needed to reach 60% of the population in the central region of Malawi within one hour? Finally we address the potential spatial components of the sustainability of input stockists relating to the potential demand from smallholder farmers and the access to bulk supplies. The problem of finding the optimum location for village-level stockists of markets is addressed in two stages, using spatial analysis in conjunction with location-allocation models. First, the locational efficiency of the existing network of stockists of inputs is determined, followed by the establishment of a set of optimal sites for village-level stockists of inputs. A final step explores the viability of stockists and calculates the population surrounding the stockists taking into account competition from other sources of inputs and the accessibility of the selected stockists to potential wholesalers who are bulk distributors of farm inputs.Our results show that locational efficiency can be assessed in terms of the differential access of households to resources and transport. Often, these differences are not considered in covering problems and can have a large effect on the physical access to inputs. The results can be used to define which areas are inherently difficult to serve with agricultural inputs and could inform efforts to provide incentives to remote areas. Further implications for input policies in Malawi are that improvements in road infrastructure might not directly benefit the poorest farmers (if they are walking) but could serve to reduce the wholesale prices and therefore the retail price. In addition, the improvement in roads might increase the number of potential customers of any particular stockist, with economies of scale allowing the reduction of prices while ensuring a satisfactory profit margin for the stockist. The results of our models imply that Citizens Network for Foreign Affairs may need to train stockists over a wider area to increase the access to inputs of those smallholder farmers with least resources. © 2011 Elsevier Ltd.

Van Asten P.J.A.,International Institute Of Tropical Agriculture | Wairegi L.W.I.,International Institute Of Tropical Agriculture | Wairegi L.W.I.,Makerere University | Bagamba F.,Kawanda Agricultural Research Institute | Drew C.,USAID Agricultural Productivity Enhancement Program
Acta Horticulturae | Year: 2010

Low soil fertility is among the important factors limiting highland banana (Musa spp., AAA-EA genome) yields in Uganda. We monitored 179 on-farm demonstration and control plots in Central, South, Southwest and East Uganda to identify constraints and opportunities to fertilizer adoption in banana systems. Demonstration plots received on average 71-8-32 kg ha -1 y -1 of N-P-K fertilizers. Most plots (53%) received external mulch, whereas farmer control plots received no fertilizer and little external mulch (13% of the plots). The demonstration plots were used for learning by nearby collaborating farmers. Structured interviews were conducted to get information on farmer perceptions of demonstrated technologies. Farmers observed that demonstration plots had consistently higher yields than control plots due to bigger bunches and better quality. Yield increases varied from 3.5 t ha -1 y -1 in Luwero (Central Uganda) to 13.1 t ha -1 y -1 in Masaka (South Uganda). Fertilizer use was highly profitable at sites close to Kampala market but not at sites far away (>250 km). The marginal rates of return exceeded 575% in Wakiso district (Central Uganda) but only averaged 10% in Bushenyi (Southwest Uganda). Foliar analysis indicated that fertilizer use will become more profitable when site-specific plant nutrient deficiencies are targeted. Farmers perceived fertilizer prices as the most important constraint to adoption, despite limited knowledge of actual prices. Other important constraints perceived by farmers were poor supply, labor required for fertilizer application, and the belief that fertilizer negatively affected soil quality. The demonstration plot approach simultaneously allowed participatory evaluation, fine-tuning and adoption and adaptation of fertilizer recommendations. This approach shortens and strengthens the adoption pathway, provided the process is supported by proper agronomic and economic evaluation of the technologies tested.

Rossmann B.,University of Graz | Muller H.,University of Graz | Smalla K.,Julius Kuhn Institute | Mpiira S.,Kawanda Agricultural Research Institute | And 3 more authors.
Applied and Environmental Microbiology | Year: 2012

Bananas are among the most widely consumed foods in the world. In Uganda, the country with the second largest banana production in the world, bananas are the most important staple food. The objective of this study was to analyze banana-associated microorganisms and to select efficient antagonists against fungal pathogens which are responsible for substantial yield losses. We studied the structure and function of microbial communities (endosphere, rhizosphere, and soil) obtained from three different traditional farms in Uganda by cultivation-independent (PCR-SSCP fingerprints of 16S rRNA/ITS genes, pyrosequencing of enterobacterial 16S rRNA gene fragments, quantitative PCR, fluorescence in situ hybridization coupled with confocal laser scanning microscopy, and PCR-based detection of broad-host-range plasmids and sulfonamide resistance genes) and cultivation-dependent methods. The results showed microhabitat-specific microbial communities that were significant across sites and treatments. Furthermore, all microhabitats contained a high number and broad spectrum of indigenous antagonists toward identified fungal pathogens. While bacterial antagonists were found to be enriched in banana plants, fungal antagonists were less abundant and mainly found in soil. The banana stem endosphere was the habitat with the highest bacterial counts (up to 109 gene copy numbers g-1). Here, enterics were found to be enhanced in abundance and diversity; they provided one-third of the bacteria and were identified by pyrosequencing with 14 genera, including not only potential human (Escherichia, Klebsiella, Salmonella, and Yersinia spp.) and plant (Pectobacterium spp.) pathogens but also disease-suppressive bacteria (Serratia spp.). The dominant role of enterics can be explained by the permanent nature and vegetative propagation of banana and the amendments of human, as well as animal, manure in these traditional cultivations. © 2012, American Society for Microbiology.

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