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Wageningen Universiteit (2006)

Participatory development of weed management technologies in Benin

Vissoh, P.V.

Titre : Participatory development of weed management technologies in Benin

Auteur : Vissoh, P.V.

Université de soutenance : Wageningen Universiteit

Grade : PhD thesis 2006

Weeds constitute a major constraint to agricultural production in the Republic of Benin. Agricultural intensification and the evolution towards permanent cropping systems have 1ed to the emergence of novel weed problems. A diagnostic study identified speargrass (Imperata cylindricd) and the parasitic weed Striga spp. as major novel weeds. Both weeds are difficult to eradicate, cause substantial food crop losses and exacerbate rural poverty through crop failure, higher labour inputs, rising costs of production and reduced availability of suitable land. Different actors reacted differently to the weed problem, in terms of the construction of knowledge, labour practices and technology development. Farmers have actively engaged in technology development and new labour practices have emerged. Researchers have not translated the new weed problem into a research priority until recently. As a consequence, inappropriate weed management technologies were proposed, and these showed low adoption. As part of the Convergence of Sciences (CoS) programme, this study attempted through a multiple stakeholder approach, using discovery learning and joint experimentation, to enable farmers to co-develop and use low-cost technologies that are effective and acceptable. The joint learning enabled farmers to better understand the biology of these weeds as a basis for choosing appropriate measures. An integrated strategy, which included deep ridging, deep hoe-weeding and shading by legumes, was more effective in suppressing speargrass than farmers’ practices. While this new strategy also improved soil organic matter and nitrogen to a subsequent maize crop, farmers’ need to bridge the hungry gap forced them to trade off legume grain production against speargrass suppression and subsequent maize yield. Farmers are also constrained by labour shortage and the lack of credit. Given their small windows ofopportunity, farmers can only gradually reclaim land that is infested by speargrass. Early planting, sorghum transplanting, crop rotation and intercropping, and trap cropping were partly effective in increasing cereal and cowpea yield and in reducing Striga hermonthica and S. gesnerioides. However, these improved practices made also clear that the Striga problem can only be addressed within an integrated crop and soil fertility management strategy. Improved weed management can be best achieved through a Farmer Field School to empower small-scale farmers to be self-reliant in finding their own solutions. Farmer self-assessment indicated that the CoS approach contributed to their increased human and social capital assets, which are a prerequisite for raising their livelihoods. The CoS approach, as applied in this study, is critically reflected upon and recommendations are made for the next phase.

Mots clés : weeds - weed control - technology - development - participation - benin - agronomy

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