The U.S. Department of the Ag­­riculture (USDA) stunned the crop markets last week with a harvest estimate that far exceeded expectations and a supply/demand report that pointed to weaker-than-expected export demand. The twin reports, released on Aug. 12, temporarily drove crop prices lower and indicated a tough market in the coming months, market analysts said.

"This is likely going to keep a lid on prices and make these markets a grind for a while," said Dale Durchholz, senior market analyst for AgriVisor, an Illinois-based crop advisory service.

Joe Camp, AgriVisor risk management specialist, said last week reports will help...