Agriculture in Niger is a complex and challenging operation. Farmers are faced with low-fertility sandy soils, variable rainfall, changing social and political situations and an unfavourable economic environment. Concerns about sustaining soil fertility have been voiced by agricultural scientists, who view agriculture as the maintenance of soil nutrient capital. Many of the biological and economic attributes of these farming systems have been documented, and are becoming better understood through the growing body of agroecological literature. Although agroecology recognises social, political and cultural interactions, much less is known about the specific details of farmers’ physical and biological knowledge and how this knowledge is used to make management decisions. Research in Fandou Be´ri village identified a local ethnopedological framework that had fundamental differences from scientific systems. Farmers’ defined soils according to location, potential for production and interaction with the wider ecological framework. They drew on varied ecological knowledge and experiences to make complex and dynamic farm decisions, as at other Sahelian villages. Local soil fertility management depends on individuals’ capabilities, perceptions of constraints and opportunities, and their ability to mediate access to different types of resources. This research suggests that there is a need to maximise the benefits of indigenous knowledge by integrating social and natural science, for example to help ‘precision farming’, and to use it to understand diversity. D 2002 Elsevier Science B.V. All rights reserved.