It's only a few days from Thanksgiving and a good share of the 2009 corn crop is still in the field in parts of northeast, southeast and south central Iowa. Some farmers wonder if it's worth it to fight the mud and try to go ahead and harvest the corn and pay to have the wet grain dried down to 15% moisture for safe storage? Also, they wonder what would happen if the harvest is delayed further, and it snows and they have to finish harvesting next spring?

"You can run into a substantial number of problems by letting corn stand in the field over the winter. It's better to try to get the corn harvested this fall, if you can," advises Roger Elmore, Iowa State University Extension corn agronomist.

As of November 15, the weekly survey by USDA showed 59% of Iowa's 2009 corn crop was still waiting to be harvested. Iowa farmers statewide can average about 5% of the state's acreage harvested per day if they have good days for harvesting. So the state may now—by November 20--have two-thirds of its crop harvested, but as you go to the southeast and south central Iowa that number increases dramatically.

Good share of the 2009 crop is still standing in the field

"We have a lot more corn still in the field in southeast and south central Iowa," observes Roger Elmore. There's quite a bit remaining to be harvested in some areas of northeast Iowa too.

How optimistic is he about further dry down of the grain in the field? "Once you get this late in the year, you're lucky if the corn drops one point of moisture per week," says Elmore. "It's going to level off in the high teens or low 20s and we really won't see much drop at all after that until we get into February or March."

"There won't be much dry down occur on corn grain left standing in the field from now through the winter because we just don't have enough heat being produced by the sun, with these short days and cold temperatures," he explains.

Consider the downside of leaving corn in the field over winter

What about farmers who are in the most adverse situations? If they were to leave the crop in the field and let it stand until the ground freezes hard, or leave it there until next spring, what is the downside of doing that?

"Agronomists have looked at that question over the years," says Elmore. "We did a study on it when I was at the University of Nebraska and we lost about 30 bushels per acre to a single snowstorm. Work from Wisconsin shows that you can lose anywhere from 20% to 60% of the yield. They were working with yields of around 200 bushels per acre in the Wisconsin study."

The amount of loss depends on how much snow you get, how much ice, how much wind. Certainly, the corn will dry down on the stalk as you get into February and March, says Elmore. But there is a high risk of some pretty severe stalk breakage and ear drop and yield loss occurring.

Big potential yield losses cause the most concern for farmers

Farmers say they don't want to leave the crop in the field over winter for other reasons too. For example, another factor to consider is damage by deer. Iowa has a huge deer population that would love to feast on your 80 acre food plot of corn during the winter.

Another downside of letting corn remain in the field is ear mold and possible mycotoxin development on the grain. Mycotoxins can play havoc with the corn's value for feed or for sale to an ethanol plant. "There's a lot of crop that needs to be harvested yet this fall because of those factors as well," adds Elmore. "Leaving corn sit in the field over winter, in my view, is not a good decision."

Of course, if you let corn stand in the field over winter you don't incur the cost of having to artificially dry the grain in a grain dryer. But the potential yield loss in the field can amount to a lot more than the money you could save by not drying the wet corn artificially.

What about avoiding the high cost of artificially drying corn?

Of course, it's better to let corn naturally dry as much as possible in the field in the fall before harvesting. That way, you don't have to pay for drying at the elevator or for propane to run an on-farm drying system. And, naturally dried corn—either on the stalk in the field or in a bin using natural, unheated air—is higher quality compared to corn dried in a high temperature drying system.

"You will lose some kernel quality when you artificially dry corn in a high temperature grain dryer, especially when the corn is coming out of the field quite wet--as it is this fall," says Elmore. "With artificial drying you also have to pay the cost of drying the corn—the propane and electricity bills," he adds. "And you do lose some quality as this corn will break up more during shipment and handling."

ISU working on survey of mold and mycotoxin situation in Iowa

This fall's harvest is certainly one of the latest and wettest in recently memory, says Gene Alt, a farmer from Audubon in western Iowa. He is hauling corn this week and says he can tell the moisture content by the weight and shape of the piles in the back of the truck. The highest moisture corn won't flatten out--it just stays up there when piled. The grain doesn't flow as well when it is wet.

Grain quality expert Charlie Hurburgh, who is director of the Iowa Grain Quality Initiative at ISU, along with ISU Extension plant pathologists Alison Robertson and Gary Munkvold, are currently working on an ear rot survey and study of mold on corn in fields this fall, to get a better handle on the mycotoxin and corn quality issues that farmers, elevators and processors face. So stay tuned for more news from that survey, as the results are expected to be released soon.