A press release from the Netherlands Organisation for Scientific Research is creating tiny ripples in the blogosphere because it suggests that fertilizer, rather than water, is what poor farmers in semi-arid regions of Zimbabwe need to improve their crops. That’s certainly one conclusion from the research of Dr Bongani Ncube, who successfully defended her doctoral dissertation 10 days ago. (Congratulations, Bongani.) More important, I think, is the demonstration that almost regardless of water, sorghum crops benefit enormously from a preceding grain legume. There’s an interaction with rainfall to be sure. In a dry year, cowpea yields more than groundnut or bambara groundnut, but sorghum is always better after a nitrogen-fixing legume. That’s not to say that farmers shouldn’t make use of a little artificial fertilizer if they can afford it. But a better strategy might be to grow a variety of grain legumes, to buffer any possible effects of rainfall, and then plant sorghum, using agricultural biodiversity instead of cash to increase the harvest.