Agro-boffins in America say that mankind could be on the verge of the "biggest agricultural breakthrough in 10,000 years", as researchers close in on "perennial grains".

At the moment, most grain grown around the world has to be replanted after every crop. Farming so-called "annual" grain of this sort consumes a lot of resources and is hard on the land, which is especially worrying as half the world's population lives off farmland which could easily be rendered unproductive by intensive annual grain harvests.

"People talk about food security," says soil science prof John Reganold. "That's only half the issue. We need to talk about both food and ecosystem security."

Reganold and his fellow dirtboffin Jerry Glover argue that perennial grain - in addition to not needing replanting, so saving on passes of farm machinery over the ground, fuel etc - would have a much deeper and more powerful root system than annuals, rather like a well-kept lawn. This would mean that it used water much more efficiently; and water is often a major issue in agriculture and its impact on its surroundings.

Other benefits of a deep perennial root system beneath farmers' fields would be less erosion and better carbon sequestration. Perhaps most tellingly of all, such a field might need as little as 3 per cent of the fertilisers required by annuals. Not only are nitrate fertilisers energy-intensive to make, they are also prone to washing out of fields to pollute water supplies, kill habitats and cause other eco mischief. Perennial fields would also require much less in the way of herbicides to control weeds.

At the moment, perennial grains capable of matching annuals don't exist. However, Reganold and Glover argue that they can be bred with sufficient effort: it's purely a matter of resources put into research. It's perhaps worth noting that there's not as much obvious revenue in perennials for major agro firms as there is in some kinds of annuals - there would be no continual requirement for new seed.

The two researchers, and many colleagues in the business, argue that with enough development cash perennial grain could be available in less than 20 years - representing, in their view, as great a step forward in food production as the original shift by the human race out of hunter-gathering and into farming in the first place.

The assembled dirt experts have convinced the editors of hefty boffinry mag Science, where their arguments are presented (subsciption required for full text). ®