Innovation in agronomy by large numbers of smallholder farmers will need to accelerate if global commitments to end hunger are to be achieved in the face of major climate and other global change that are both caused by, and impact, agriculture. Conventional research and development in agronomy have involved a research process that produces technologies, which are then promoted for uptake by large numbers of farmers through extension, with both research and extension phases being more or less participatory. Recent research, including key contributions to this special issue, reveals that the performance of many technology options varies hugely across the geographies over which development programmes operate, depending on social, economic and ecological context. This severely limits the value of attempting to produce recommendations for large areas and numbers of farmers and identifies the need for new ways of supporting innovation that address the real-world heterogeneity of farmer circumstances. Addressing this widespread phenomenon of option by context interaction (OxC) has profound implications for how agronomic research and development are organised. Papers in this special issue show the nature and implications of such interactions and suggest ways in which research and development systems need to respond in order to support locally relevant innovation. It is evident that a paradigm shift is well underway, with researchers embracing new modes of thinking and action required to address OxC interactions, but these also need to be taken up and further developed by extension and change agents in the public and private sector. It is only through continued co-development of methods involving both these constituencies, working closely with farmers that sufficient progress is likely to be made for smallholder farming to keep pace with global demand for food without further damaging the environmental resources upon which production is based.