Smallholder farmers in semi-arid Africa are in an increasingly vulnerable position due to the direct and indirect effects of climate change, demographic pressure and resource degradation. Conservation agriculture (CA) is promoted as an alternative to restore soil productivity through increased water and nutrient use efficiencies in these regions. However, adoption of CA is low due to a number of technical reasons, but fundamentally due to the fact that CA has been often promoted as a package, without proper adaptation to local circumstances. Farmers engagement in designing and implementing locally suited CA practices, as part of a long term strategy of soil rehabilitation is the core approach followed by the ABACO initiative, which brings together scientists and practitioners from West, East and Southern Africa coordinated through the African Conservation Tillage Network (www.act-africa.org). ABACO relies on agro-ecologically intensive measures for soil rehabilitation and increased water productivity in semi-arid regions, implemented, tested and disseminated through local co-innovation platforms. Rather than using rigid definitions of CA approaches that might not work in all sites, ABACO proposes to explore best engagement approaches for different sites. Simulation modelling is used as a support of long-term cross scale tradeoffs analysis from field to farms and territories, in order to inform effective policy-making. Preliminary results form the field are used here to illustrate and discuss the principles of ABACO, which may apply as well to regions other than semi-arid Africa.