Sustainable agricultural development in sub‐Saharan Africa: the case for a paradigm shift in land husbandry

Abstract In order to tackle poverty and hunger in sub‐Saharan Africa (SSA) there is a strong case for a focus of effort on improving rainfed agricultural systems. The challenge is to deliver a transformation of agricultural productivity in such systems without adverse impacts on environmental goods and services. We examine the growing advocacy of ‘conservation agriculture’ (CA) as the desired approach and assess the evidence to support the assertion that it can deliver sustainable agricultural development in SSA. We examine in particular the evidence which derives from experience with ‘zero tillage sustainable agriculture’ in Brazil. We ask the question, is there a case for a paradigm shift in land husbandry? The case for a paradigm shift hangs on the premise that conventional practice promotes land degradation, while adoption of CA practice delivers a range of benefits through promoting soil ecosystem health. The guiding principle is to promote biological tillage through minimizing mechanical soil disturbance and maintaining permanent organic soil cover. We examine evidence of benefits in the context of the wider debate on low‐external‐input technology. We conclude that CA does not overcome constraints on low‐external‐input systems and will deliver the productivity gains that are required to achieve food security and poverty targets only if farmers have access to fertilizers and herbicides. We conclude also that widespread adoption of the new paradigm amongst millions of small farmers in order to achieve the ‘doubly green revolution’ in SSA is subject to the familiar constraints of knowledge transfer and success will depend upon creating innovation networks. Further, we conclude that amongst small‐scale farmers partial adoption will be the norm and it is not clear that this will deliver soil health benefits claimed for full adoption of the new paradigm.