USDA's latest crop progress report  shows that U.S. corn growers continue to make slow planting progress. According to yesterday's report, 48 percent of the corn acreage is now planted, compared to 51 percent a year ago. The five-year average for this date is 77.4 percent.

Perhaps more important is the fact that the current planting rate is only 8 percent higher than in 1993, which was the slowest pace on record, point out economists Steve Meyer and Len Steiner in the CME Daily Livestock Report.

The cool wet spring has kept corn growers out of the fields in much of the Midwest and delayed planting progress. Illinois, Indiana, Ohio and Michigan are facing particularly wet fields. The progress in those states are reported at 10 percent, 11 percent, 22 percent and 18 percent respectively of their acres planted. Five-year averages for those states should range from 60 percent to 80 percent by this time in the season. In 2008, those states produced 30 percent of the nation's corn crop.

The western Cornbelt is better off, with Iowa, Nebraska and Minnesota all running ahead of the 5-year average, and these states harvest 40 percent of all U.S. corn.

Soybean plantings reflect similar patterns, with excess moisture in the east. In total, only 14 percent of the crop is in the ground. Last year's pace was slower, with 11 percent of the crop planted by May 10, but the five-year average runs nearly 32 percent. Of course, soybeans can be planted later into the spring than corn.

For more a look at USDA's Crop Progress report, click here