Résumé
The Unaí Project (Brazilian Cerrados) uses a participatory approach inspired by the principles of Action-research to strengthen innovation processes within the context of the Agrarian Reform Sector. It associates as partners scientists, farmers, trainers and development agents and focuses both on the socio-technical and organisational dimensions of innovation. This paper presents the results of a sociological assessment of the encounter between farmers and scientists in connection with the development of knowledge related to direct seeding cropping systems within the framework of the Unai project. The objective was to analyse the complementarities and difficulties in terms of knowledge exchange and production. There was convergence of representations between farmers and researchers about the practical issues related to direct seeding. But there were differences about the overall role of direct-seeding and specifically of cover crops in the production process. Farmers and researchers did not share the same perception of the value of participation, with the former placing a premium on affective and social factors. Farmers' participation in the conception of innovations has several methodological implications, including the necessary formalization of roles and responsibilities of each actor and the development of intermediary actors.