Waning levels of growth in farm productivity represent the grains industry's most important problem, a leading scientist has said, forecasting that genetically modified wheat is at least a decade away.

In Australia, the rate of expansion in cereals productivity had slowed markedly from 2.1% a year in the two decades to 2007-08, when it was "considerably higher than other commodity groups", said Peter Reading, head of Canberra-based Grains Research and Development Corporation.

However, this was an illustration of a "worrying" worldwide slowdown at a time of growing demand for grain.

"The decline in the rate of productivity growth is the principal challenge facing the international grains community," Mr Reading told the International Grains Conference in London.

Spending dries up

The decline reflected in part temporary factors, such as drought in Australia, and in part the passing of the green revolution and a period of relatively easy wins, through factors such as the spread of mechanisation and best crop management.

However, it also reflected a fall in research spending, which in Australia had dropped to 3% of the gross value of farm production, from 5% in the late 1970s, with similar trends elsewhere, including America.

Yet developing characteristics such as drought tolerance needed to reboot productivity growth was a "much more challenging" task.

"Declined rates of investment could negatively impact productivity growth for a considerable period," he said.

Indeed, genetically modified wheat, one route to raising yields, was unlikely to be available on a commercial basis for at least a decade.