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Swedish University of Agricultural Sciences (2019)

Integrating legumes in mixed crop-livestock systems in east Africa : Farmers’ perceptions, ecosystem services and support for decision making

Muoni, Tarirai

Titre : Integrating legumes in mixed crop-livestock systems in east Africa : Farmers’ perceptions, ecosystem services and support for decision making

Auteur : Muoni, Tarirai

Université de soutenance : Swedish University of Agricultural Sciences

Grade : Doctoral Thesis 2019

Résumé
Challenges faced by smallholder farmers in east Africa include limited access to inputs, small farm sizes, and erratic rainfall patterns. Legume intensification and species diversification have been recommended for improving food and nutritional security, controlling soil erosion, improving soil fertility, supplying income and providing fuel. The aim of the thesis was to assess the various contributions legumes make in integrated crop-livestock systems and to facilitate their efficient use. The approaches used included : 1) an on-farm survey of 268 farmers in Kenya and Democratic Republic of the Congo to assess farmers’ perceptions of legumes and their functions ; 2) a metaanalysis on the effects of crop management practices on legume productivity and biological nitrogen fixation (BNF) in sub-Saharan Africa ; 3) an on-farm experiment in Kenya investigating the effects of crops and crop mixtures including legumes on soil erosion control ; and 4) providing inputs from literature review and experimental results to further develop the LegumeCHOICE decision support tool. Results showed that farmers appreciated legumes more for their food and income functions than for provision of fodder, fuel, soil fertility or erosion control. Furthermore, according to survey work, the concept of “legumes” had little meaning for farmers. The metaanalysis showed that crop management practices directly influenced legume productivity. Intercropping increased the total land equivalent ratio (LER). Focusing on the legume component, pigeon pea (Cajanus cajan) had a relative LER of 90%, while for species such as groundnut (Arachis hypogea) and common bean (Phaseolus vulgaris) the figure was around 60%. Inoculation and phosphorus (P) application increased legume grain and biomass yield, and species and soil type helped explain the variation of legume productivity in response to those management practices. Inoculation also increased the amount of nitrogen (N) fixed by legumes. Experimental work showed that incorporating different crop types and crop mixtures with legumes increased rainfall infiltration and earthworm population, and reduced runoff and soil erosion. Calliandra hedgerows, mulching and sole Mucuna reduced soil erosion and runoff more than maize/common bean intercropping. Developing literature-derived values as a complement to the expert scores, which presently underlie the LegumeCHOICE tool improved the relationships between the scoring and actual provision of food, livestock feed and soil fertility improvement using grain and biomass yield and BNF as proxies. This thesis shows that farmers in east Africa have some knowledge about legumes although their perception of the various functions legumes provide is limited. Despite heterogeneity of smallholder farming systems, legumes respond consistently to intercropping, inoculation and P-application. Combining literature values with expert scores enhanced the validity of the LegumeCHOICE tool for supporting farmer decision making.

Mots Clés  : grain legume, herbaceous legume, intercropping, soil erosion, sustainable intensification, tree legume

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Page publiée le 27 mai 2020