Outlook on AGRICULTURE Vol 41, No 3, 2012, pp 171–178 doi: 10.5367/oa.2012.0094 171 Agronomic and economic performance of yam- based systems with shrubby and herbaceous legumes adapted by smallholders Raphiou Maliki, Denis Cornet, Anne Floquet and Brice Sinsin Abstract: West Africa has major problems relating to the impact of slash-and-burn shifting cultivation on soil systems. In order to design more sustainable yam cropping systems, agronomy research in Benin has implemented trials in partnership with smallholders on alternative yam-based systems using shrubby (Gliricidia sepium) and herbaceous (Aeschynomene histrix) legumes. In the first phase, farmers modified these new systems within their own constraints; the systems were then further evaluated. The agronomic and economic performance of farmer-adapted alternative yam-based cropping systems and the implications for wider international application are discussed. Keywords: adaptive research; yam-based systems; net present value; modelling; Aeschynomene histrix; Gliricidia sepium Raphiou Maliki (corresponding author) is with L’Institut National des Recherches Agricoles du Bénin (NRAB), BP 01-884, Cotonou, Benin. E-mail: malikird@yahoo.fr. Denis Cornet is with Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), F-34398, Montpellier Cedex 5, France. Anne Floquet is with Centre Béninois pour l’Environnement, le Développement Economique et Social (CEBEDES), BP 02-331, Cotonou, Benin. Brice Sinsin is with Faculté des Sciences Agronomiques de l’Université d’Abomey-Calavi (FSA/UAC), BP 01-526, Cotonou, Benin. West Africa currently produces more than 40 million t year –1 of yam, which equates to 90% of total worldwide production (FAOSTAT, 2010). Increases in production have been obtained on larger yam-cultivated areas in slash-and-burn and shifting cultivation systems (Torquebiau, 2007), indicating that only a limited degree of intensification was under way. Benin is the world’s fourth ranked producer, after Nigeria, Côte d’Ivoire and Ghana. Farmers no longer rely on long-duration fallow between crops as yam is cultivated in one- or two-year herbaceous fallow–yam or maize/sorghum–yam rotation systems with manual incorporation of residue into the soil (Doumbia, 2005). In order to design a more sustainable yam cropping system, agronomy research in Benin has focused on trials in partnership with smallholders on alternative yam-based cropping systems using shrubby (Gliricidia sepium) and/or herbaceous (Aeschynomene histrix) legumes. The most important constraints for agroforestry systems adoption, notably alley cropping (Kang and Reynolds, 1986) are its pruning workload as well as competition between shrubs and crops for nutri- ents and light (Floquet et al, 2006; Maliki, 2006). It is well known that smallholders adjust technologies developed by researchers when confronted with various