From Matthew Stevens, Sydney, Australia
The goal of incorporating symbiosis machinery in the roots of non-legume crop plants is worth the investment, but we can never “get rid of chemical fertilisers” totally. Even if we establish bacterial symbiosis in grass crops, for example, and then apply composted animal and human manure, to be able to produce enough food to feed the world’s population, we must maximise the productive capacity of both fertile and marginal land(28 June, p 35).
As crop harvesting removes soil nutrients from the land, we have no choice but to replace them. Nitrogen-fixing rice and wheat would be an enormous boon, but we can’t stop the loss of nutrients to the oceans, so we will at least have to keep applying phosphorus, potassium and trace elements.
