seal  Purdue News

September 11, 2003

Corn looks dry, but still 'wet' inside the ears, Purdue experts say

WEST LAFAYETTE, Ind. – Late-summer weather has Indiana cornfields looking dry and parched, but appearances are deceiving.

Inside the husk, kernel moisture content remains high – 25 percent or more in many fields. With the crop season rushing toward conclusion, farmers could be forced to harvest corn before it dries down naturally, said Bob Nielsen, Purdue University Cooperative Extension Service corn specialist. He said producers might have to dry corn in grain dryers and bins, despite high propane gas costs.

Moisture content of 15 percent or lower is recommended if farmers intend to put grain into storage. Greater moisture levels can cause stored grain to spoil.

"The biggest issues for corn are the wetness of the grain and the impact that has on farmers' decisions to start harvesting, the risk of stalk rot developing in fields and the need for growers to walk their fields the next couple of weeks to determine whether stalk rot is developing," Nielsen said.

"We can't stop stalk rot from developing. But if folks can determine which fields are at the highest risk of both stalk rot and, ultimately, stalk lodging, that may allow them to tailor their harvest schedules and try to harvest those fields earlier."

Corn harvest is expected to begin in earnest before month's end, Nielsen said. The crop is "wetter" at this point in the growing season because so many acres were planted late or replanted after spring storms destroyed emerged crops.

While corn is too moist to store, it might soon be dry enough to harvest, Nielsen said.

"Farmers prefer to harvest grain not much wetter than the low 20 percent moisture level and, preferably, below 20 percent moisture, because they feel it harvests much easier in the field," he said. "That's somewhat in contrast to what data suggests. Most research suggests that the optimum grain moisture content that minimizes mechanical crop loss on the dry side and kernel damage on the wet side, is somewhere in the mid-20s.

"I think everyone would agree that harvesting in the high 20s or higher is not desirable because of the damage to those kernels that are still a bit soft and can more easily break up."

Farmers with large corn acreage likely will begin harvesting the crop while grain moisture is about 25 percent and hope to complete harvest with moisture levels at 20 percent or less, Nielsen said.

On sunny, warm September days, corn can lose 1 percent moisture or more per day. Moisture loss falls to between 0.25 percent to 0.50 percent per day in October. By early November natural drying in the field essentially stops.

Although recent weather patterns have been warm and dry, a change could mean trouble for producers with corn still in the field.

"Sometimes we get into patterns of rainfall that make it a real problem harvesting as we get further into October," Nielsen said. "Then there's a risk of the corn crop not standing as long as we want it to and stalk breakage occurring, with mechanical harvest loss as a result.

"This year the risk is even higher. A lot of fields have been stressed all summer long, either by the various monsoon rain events that we've had or by the dry period in August. Root systems are not as healthy as they ought to be because of all this. The risk of root rots and stalk rots developing in these stressed fields is pretty substantial. If a person decides to let a field sit there and dry naturally, they are risking a late-season storm that could lay that field flat."

Farmers choosing to harvest corn and complete the drying process artificially can pick up pointers to optimize drying systems and save money at Purdue's Post Harvest Grain Quality and Stored Product Protection Program Web site, located at, said Dirk Maier, Purdue Extension agricultural engineer.

This fall also might be the time to consider an old drying technique, Maier said.

"One of the methods many people used to practice is what we call dryeration and in-bin cooling," he said. "In that process you dry your grain to about 17 or 18 percent moisture, transfer it into a steeping bin and let it steep for eight to 12 hours, cool the grain and move it into a final storage bin."

The practice isn't ideal for every situation, but it could help many farmers in the long run, Maier said.

"When corn is harvested in the low 20 percent moisture range, or even around 19 or 20 percent, the dryeration process isn't as effective because you're not removing that much moisture initially before you get into the steeping process," he said. "However, when you're harvesting 24, 25 or 26 percent moisture content corn, transferring it hot at 17 or 18 percent and then taking the last three or four points of moisture out during the cooling process becomes very effective in overall energy savings and overall capacity of the drying process."

Writer: Steve Leer, (765) 494-8415,

Sources: Bob Nielsen, (765) 494-4802,

Dirk Maier, (765) 494-1175,

Related Web sites:

Chat 'n Chew Café:

Purdue University Department of Agricultural and Biological Engineering Extension:

Purdue News Service: (765) 494-2096;

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