The New Ag Talk Forum lists a traditional method of determining that ear corn is ready to be picked and cribbed if 7 or 8 out of 10 ears will float in a tub of water1
The concern with moisture in stored corn is that if it is high enought the corn will mold or heat (rot). Excessive shuck of the ear promotes mold and impedes drying during storage
Purdue University states ear corn should be cribbed at 20% moisture2. While the University of Wisconsin states 20 to 22% moisture ear corn can be stored in cribs
7 to 8 feet wide and while 25% moisture ear corn may be stored in cribs 4½ feet wide3. For larger diameter cribs, the University of Kentucky suggests that ear corn
be 18% moisture or less4.
Both the Purdue and Kentucky sources show an American Society of Agricultural and Biological Engineers (ASABE) table that shows that while the kernals
are at 30% moisture the cob is at 52% moisture. At 13% moisture the kernals and cob have equal percent moisture. And at 10% kernal moisture content the cob will have 9%2,4.
The Farm Progress article discusses that shell corn is specified as weighing 56 pounds to a bushel and occuppies 1¼ cubic feet. Ear corn with the added cob weighs 70 pounds and occcupies 2½ cubic feet per bushel5.