The Centre de Cooperation Internationale en Recherche Agronomique pour le Developpement has conducted collaborative research with national agricultural research services in several semi-arid regions that has led to a general understanding of the relationship between water consumption and growth, and crop responses to fertilizers However, farmers' adoption of practices arising from the research has been minimal Current effort is directed at overcoming limits to adoption, firstly by understanding the interaction of fertilizer response and water supply, especially through modelling, in order to quantify risk criteria from the farmer's point of view. Secondly, research now takes account of the whole cropping system, including labour availability, access to credit, livestock management, etc, with a multidisciplinary approach. Approaches that offer sustainability are improved intercroppmg systems, retention of crop residues, increased plant cover, and agroforestry. There are important technical gaps in understanding of how these systems should operate. The allocation of nutrients and water among the components of intercropped or agroforestry systems is not understood and solutions could lead to improved spatial arrangements. The integrated effects of residues on runoff, soil evaporation, crop transpiration and N mineralization are not quantified In these and other problems, the full range of risks as well as benefits need to be evaluated