Washington's assessment of an annual rise of 862m bushels (21.9m tonnes) in US corn stocks appears small against a 1.06bn-bushel increase in estimated production of the grain, University of Illinois economist Darrel Good said.

The data implied a rise of 6.5% in use of corn by US livestock farmers - a "large increase" which was "counterintuitive" given livestock sector woes and increasing competition from distiller's grains.

"The large level of use may imply an overestimate of the 2009 crop," Good said.

For soybeans, the US Department of Agriculture's estimate of a 61m-bushel rise year-on-year rise in US inventories as of the beginning of December appeared small given a 322m-bushel jump in supplies.

While buoyant exports had soaked up much of the extra crop, Good highlighted a doubling to 185.3m bushels in the amount of soybeans put down for seed, feed and residual use – a figure which beat the 2003 record by a margin.

"On the surface, the large disappearance suggests the 2009 crop may have been overestimated," Good said, adding that details would become clearer when the US Department of Agriculture's next stocks data were released at the end of March.