US statisticians may have overestimated the surge in US corn yields, a leading agricultural economist has said, while warning investors not to expect too much of a current revival in prices.

The US Department of Agriculture last week hiked its forecast for this year's corn yield to 159.5 bushels per acre, with many observers predicting more rises to come.

"Based on the adage that large crops tend to get larger, there is some expectation that the yield forecast will increase in subsequent reports," University of Illinois economist Darrel Good said.

'Severe hail damage'

However, the evidence for corn reaching this potential was "mixed".

"Some severe hail damage in key Iowa growing areas and some very dry weather in other corn-growing areas during the first half of August may have reduced yield potential," Mr Good said.

Furthermore, the crop's condition was, according to USDA data, only marginally better than last year, when yields came in at 153.9 bushels per acre.

A University of Illinois model, based on crop conditions, forecast a yield of 158.5 bushels per acre, implying that the harvest will come in 104m bushels (2.64m tonnes) lower than the official 12.76bn-bushel estimate.

Demand question 

Nonetheless, Mr Good forecast that expectations of a better crop would, going into the harvest season, "likely keep some pressure on corn prices", which staged a modest rebound on Tuesday, adding 0.4% in Chicago.

Furthermore, a USDA forecast that 1.62bn bushels of US corn would be consumed in the year starting in September looked "generous".

"Beyond harvest, corn prices will be influenced by the rate of consumption and the extent of US and world economic recovery," he added.

Mr Good last month rocked Chicago markets by warning that the USDA's then yield forecast of 153.4 bushels per acre was considerably too low, although his estimate at the time of 163.2 bushels per acre now appears generous.