The challenges facing global agriculture via population increase, climate change and dietary choices are unprecedented and urgent. In the context of declining public funding for research and development in agriculture (ag R&D), we highlight the historically high returns on such investments and outline an economic rationale to continue government involvement through support and policy ag R&D. Next, we illustrate the substantive agricultural impact of science and technology, and reveal cases where oversimplification, reductionism and lack of rigor compromise returns on investment. Ex situ conservation of genetic resources, organic agriculture, soil health and the water footprint illustrate issues that need attention because they feature flaws in important aspects of agricultural theory or practice with implications for policy and investment. We conclude with high-level propositions for improved allocation of ag R&D resources.