In spite of the green revolution of the 1990s, guaranteeing food security remains a challenge in large parts of the mountains of Southeast Asia. It is largely accepted that the most suitable farming systems for the uplands are based either on tree crops or mixed crop-livestock systems, both to manage the soil fertility and to maintain the soil in place. How can this be applied for a sustainable farming system? This project, from the DURAS international program to promote sustainable development in agricultural systems, aims to develop and enhance sustainable agriculture that makes the best use of: 1) the local knowledge and skills of farmers; 2) social capital - people's capacities to work together to solve common management problems; 3) nature's goods and services; and 4) public goods - rural jobs, clean water, flood protection, landscape quality, etc. More specifically, the Vietnamese part of this project works specifically on a better understanding of local-knowledge implications from the disadvantaged communities living in mountainous areas through the spontaneous innovations of farming systems. Local participation has been strengthened along the research and extension processes by a case study: the introduction of fodder crop in the farming system. After completion and evaluation of the first round of fodder tests within experimental plots, on-farm tests have been conducted under farmer management for the most promising species. The farmers selected the fodder species (temperate and/or tropical), the planting place (upland and/or lowland) and the surface on which to cultivate. Interactions with farmers and local extension officers were initiated at the very onset of the project through a former project on watershed management (MSEC program). In addition, experiments and surveys of fodder crops (yield, harvesting and forage management, agricultural calendar etc.) were conducted in close cooperation with farmers in their own fields. Dissemination of the results o