The crack detected in Chicago earlier this week between firm soybeans and sagging grains widened into a fissure, reflecting a monthly US report on global crops which proved more momentous than many investors had expected.

"In what was expected to be a pretty mundane report, the US Department of Agriculture managed to come out with some humdinger of some corn and wheat numbers," Benson Quinn Commodities said.

The key data for corn were upward revisions to both US and world inventories, reflecting weak American exports and strong Argentina and South African crops. A raise to the estimate for America's year-end wheat stocks was unexpected too, lifting them over 1bn bushels for the first time in 22 years.

'Wild morning'

The result was what Darrell Holaday at Country Futures called a "wild morning" with grains fighting between bearish forces from the USDA report and supportive oil, which was helped by petrol inventory data, and dollar.

The bears won. March wheat closed down 1.6% at a one-month low of $4.70 ¾ a bushel in Chicago, with its May colleague losing 1.6% to $4.81 ½ a bushel. Kansas wheat also closed lower, if slightly less steeply, so widening its premium.

Corn did a little better, shedding 0.9% to $3.55 ½ a bushel for March and the same to $3.65 ½ a bushel for May.

The clear winner was the soybean, which closed up 1.1% at $9.52 a bushel for March, the fourth successive positive close, and 10.8% at $9.58 a bushel for May delivery.

It received a considerably better time from the USDA, which lowered its estimate of America's year-end stocks by 30m bushels to 190m bushels, more than traders had expected.

'Fundamental supply bear market'

Not that analysts were unanimous in their glee.

"The soybean US ending stocks at 190m bushels is slightly positive but will be muted by the large South America crop and world competition," broker US Commodities said.

"We are in fundamental supply bear market in wheat, followed by corn, and soybeans may soon enter if South America's crop materialises."

Country Futures went even further.

"When you stand back and look at the big picture, the feel you get is that the world is really dragging from a consumption standpoint, with the exception being China," the broker said.

"In addition, production levels have been very solid with no significant challenges. There is simply a large amount of inventory to chew through in the world and, other than China, the overall global economy is chewing very slowly."

Upbeat pocket

Signs of optimism appeared hard to find, although Vic Lespinasse, the GrainAnalyst.com analyst, found one in soyoil, which had a "strong supportive background feature" in firm prices of its biggest vegetable oil competitor.

"The very narrow premium soybean oil currently commands over palm oil is encouraging demand for bean oil relative to palm oil, a strong supportive background feature," Mr Lespinasse said.

March soyoil closed up 1.7% at 40.69 cents a pound, its strongest for two months.