A third of Argentina's farms no longer use the plough. Instead, they fight weeds by planting winter crops such as black oats, or by spraying a biodegradable herbicide such as glyphosate. Zero-tillage also benefits the planet in general. Unploughed soils hang on to carbon that would otherwise escape into the air as carbon dioxide when organic matter rots. A one-hectare field left unploughed can absorb up to a tonne of carbon every year, says Pretty, making soils a vital element in preventing global warming.
Sustainable agriculture is no magic bullet for feeding the world.
It is an approach rather than a blueprint. Small farms with low yields stand to benefit the most and agribusiness the least. But it does offer an alternative for the millions of small farms that have plenty of hands to work the land but not the skills or financial resources to adopt conventional mechanised farming. If it catches on we can make substantial inroads in reducing the 800 million people who still go to bed hungry every night. Perhaps the most dramatic evidence of its success so far, he adds, is that little of the extra produce ever finds its way to distant supermarkets while the farmers starve.