Linn Group, a brokerage firm, predicted Wednesday that the U.S. corn and soybean harvests would fall short of the latest government estimates.

The Chicago-based firm pegged the 2011 corn crop at 12.775 billion bushels, with an average yield of 152.1 bushels per acre. It estimated the soybean crop at 3.148 billion bushels, with a yield of 43 bushels per acre.

By contrast, the U.S. Department of Agriculture in July estimated the U.S. corn crop at 13.47 billion bushels, using a 158.7-bushel-an-acre yield, and soybean output at 3.225 billion, using a 43.4-bushel-an-acre yield. The USDA is scheduled to release updated figures next week.

Linn Group said heat and dryness in July hurt the corn crop, noting that crops in central Illinois and Indiana were "of particular concern." The firm warned that "deterioration has the potential to lower yields more than what happened last year." The average U.S. corn yield in 2010 was 152.8 bushels an acre.

Linn Group had a brighter outlook for soybeans. The firm said it was "cautiously optimistic about U.S. soybean yield prospects, with weather maps implying fairly good growing conditions for early August."

The estimates make Linn Group the latest private firm to project smaller crops than the USDA. On Tuesday, brokerage firm FC Stone predicted U.S. farmers will harvest 13.002 billion bushels of corn and 3.145 billion bushels of soybeans.