Soybean prices fell to their lowest for nine months after US statisticians admitted that they had vastly underestimated soy production data - including missing an area bigger than Rhode Island from last year's planting numbers.

The US Department of Agriculture put the amount of bushels in farmers' and commercial stores at 205m bushels, roughly 60m bushels more than investors had expected.

The department also raised by 1.11m acres - equivalent to 1,700 square miles, or three times the area of London - its figure for soybean plantation in 2007. The acreage harvested was raised by 1.32m acres, with the USDA's bean production number revised up 90.6m bushels to 2.68bn.

In Chicago, November soy closed down $0.49 a bushel, or 4.5%, at $10.45 a bushel. December soymeal lost $16.40 to $285.00 a short ton, with December soyoil closing 95 points lower at $0.4448 a pound.

Even at 205m bushels, US soy stocks were still tight at the start of the month - 64% lower at the start of the month than a year before, with enough in store to meet only about one month's demand.

However, a USDA supply /demand report two weeks ago had indicated stocks of about 140m bushels. A 35m-bushel deficit listed under "residuals" had raised suspicions among some observers that the figure was an underestimate.