Wheat's declining popularity among farmers is "unsustainable", given the growth of more than one-third in demand for the grain expected over the next 40 years, according to reports.

World wheat sowings have been in decline since the early 1980s, as farmers turn increasingly to corn and, especially, soy, for which plantings have quadrupled to some 100 million hectares since the early 1960s, Vince Petersen of US Wheat Associates said.

But the slowdown in production growth was a "danger signal going forward" as the world grapples with population growth of more than two billion people by 2050, coupled with increasing per capita consumption of wheat thanks to the growing popularity of biscuits and bread, he said.

Furthermore, most of the population growth was set to occur in tropical countries unsuited to wheat production, with less in grain powerhouses such as Australia, Europe and Russia.

The discrepancy boded well for wheat exporters, to meet the growing demand in areas such as central America and equatorial Africa.

Trade in these areas had already increased by some 250% to 125 million tonnes since 1980, and looked likely to see another 250% increase over the next 30 years.

Petersen urged a conclusion to free trade talks being fostered by the World Trade Organisation as a method of encouraging a stable wheat market during an era of growing demand.

While this would mean farmers in protected Western markets giving up government support, they would swap it for access to markets with fast-growing populations.

Sticking with the status quo, and relying on markets as currently structured to nurture production, risked a return to price spikes as seen two years ago, when importers paid US$700-800 a tonne including freight to ship in the grain.