Farming's period of high profits is over, agricultural economists have said in a report which warns that US corn and soybean farmers will fall into the red for the first time in at least 20 years.

Corn farmers, who last year earned a profit of $228 per acre, face a loss of $8 per acre in 2009, a University of Illinois report said.

Soybean growers will lose $15 on every acre, compared with a $108-an-acre profit last year.

And the profitability declines, which reflect higher payments for fertilizer, seed and pesticides at a time of declining crop revenues, look unlikely to be fully reversed, the report added.

"It's likely that the high returns period experienced during 2007 and 2008 is over, and crop farming now faces agricultural returns closer to historical averages," University of Illinois economist Gary Schnitkey said.

'Financial stress' 

The report added that many farms "will likely face financial stress" because of the losses, which are likely to differ from operation to operation, and are the first of the 1990s and 2000s.

"There will be sizable variations in non-land costs across farms, as fertilizer prices varied greatly between the fall and the spring," Mr Schnitkey said.

"Timing of purchase will have a large impact."

And the losses may increase further if commodity prices renew their post-summer declines.

"Changes in commodity prices have the most potential to change returns," he said.

Chicago corn stood at $3.24 a bushel on Friday, 28% below its 2009 high reached in June.

Soybeans were, at $9.56 ¼ a bushel, down 26% on their high for the year, which was also reached in June.