The Smallholder System Innovations (SSI) program is a multidisciplinary applied research program with direct relevance to rural development. It addresses the environmental, social and institutional conditions required to enable a sustainable upgrading of rainfed agriculture among smallholder farmers in water scarce tropical and sub-tropical environments. It thereby contributes to security on livelihood and poverty alleviation in rural communities of sub-Saharan Africa. The program is carried out in two river basins (the Thukela river basin in South Africa and the Pangani river basin in Tanzania) representing typical semi-arid to dry sub-humid climates.