The US inventory data reflected expectations of US growers achieving, besides large sowings, a record yield of 166.0 bushels per acre this year, a figure 2.0 bushels per acre higher than the USDA's initial estimate.

Furthermore, US corn exports, while seen rising 200m bushels in 2012-13, will be limited by "record foreign corn supplies", Mr Gutter said.

Ukraine's crop was pegged at a record 24.0m tonnes, with Argentina's forecast rebounding by 3.5m tonnes to 25.0m tonnes.

'Something wrong with that number'

The extra supplies were seen curtailing price prospects, with US farmers seen receiving $4.20-5.00 a bushel for this year's corn, a figure Mr Gutter acknowledged was "down sharply" from the $5.95-6.25 a bushel they are set to receive for last year's crop.

At Teucrium Trading, Sal Gilbertie said: "This is a very significant decrease. The entire US farm economy is going to have to adapt quickly back to lower prices for corn."

Furthermore, the US stocks figure might, even at 1.8bn bushels, still prove an underestimate, given that it includes a 900m-bushel increase in feed and residual use, reversing a four-year downward trend.

"There is something wrong with that number. It is almost going back to the days before distillers' grains," the byproduct of ethanol manufacture used as an alternative to corn in animal feed.

Price reaction

In Chicago, corn for July plunged 3.3% to $5.87 ½ a bushel in early live deals in Chicago.

The new crop December contract touched $5.05 a bushel at one point, its lowest since February last year, before closing at $5.07 ¼ a bushel, down 1.8% on the day.