USDA will release its 1 September quarterly stocks report this Friday. These quarterly stocks reports have been very tricky to interpret recently, especially the corn numbers. There have been inexplicable periods of larger-than-expected disappearance followed by inexplicable periods of smaller-than-expected disappearance. Friday's quarterly stocks report offers every opportunity for more "tricks" for several reasons.

The corn harvest was the farthest advanced in August it has ever been. Based on harvest progress during the last week of August, it is possible that as much as 500-750 million bushels of 2012 crop corn was harvested prior to the 1 September report date. The soybean harvest was also advanced, but not to the extent of the...