According to Good, concerns about the size of the 2011 U.S. corn crop stem from two sources. One is the potential loss of corn acreage due to flooding in southern areas and the slow planting progress in a number of states.

"Corn acreage, however, may have exceeded intentions in areas where planting was more timely. Speculation about the magnitude of planted and harvested acreage will continue until June 30 when the USDA releases the Acreage report. Some of the early estimates of lost acreage appear to be overstated," he says.

The second source of concern about the size of the 2011 corn crop is the late planting that is occurring in some areas. Through mid-month, planting had progressed at a very slow pace in Indiana, Kentucky, Michigan, Minnesota, North Dakota, Ohio and Wisconsin, he says.

"It appears that more than the average amount of the U.S. corn acreage will be planted after the optimum date for maximum yield potential. Yield potential, however, is still unknown since weather conditions in July and August are very important for determining yields. The market will monitor USDA's weekly report of crop conditions to evaluate yield potential as the growing season progresses," he says.

Corn prices began a steep climb beginning June 30, 2010, when the USDA revealed smaller-than-expected planted acreage of corn and smaller-than-expected June 1 stocks of corn. The rally was then fueled by declining yield prospects and strong demand, he says.

"June 30, 2011, is also setting up to be a pivotal day for corn prices. USDA reports will reveal stock levels and acreage, and summer weather prospects will be clearer," Good says.