The number of crop acres Iowa farmers are unable to harvest this fall as a result of the August derecho windstorm has increased to 850,000 acres. USDA released the updated estimate in its Oct. 9 crop report. It’s an increase of more than 50% from September, when USDA estimated the loss to the Aug. 10 derecho totaled 550,000 acres of mostly corn and some soybeans.

With winds in excess of 100 mph and gusts up to 140 mph in some locations, the storm flattened and tangled cornstalks in a wide area across the state’s midsection from western to eastern Iowa. Crop damage was compounded by drought during summer and into fall in much of Iowa. After some rain in September, the drought expanded again in October.

Iowa Secretary of Agriculture Mike Naig tells Wallaces Farmer that he expects the number of lost acres will climb even more before harvest 2020 is completed. More fields will likely be considered a total loss. In most cases, farmers with downed corn are trying to harvest as much of it as they can. But it’s a slow and costly process, and in the worst cases, many farmers are asking crop insurance adjusters to return to these fields to conduct another inspection.

Greater challenge than expected

“I’m hearing that more farmers are finding it more difficult to harvest these flattened cornfields than they anticipated,” Naig says. “Also, stalk quality deteriorates the longer the corn is in the field. The weakened stalks often break off. Unattached stalks tend to push in front of a combine’s corn header, and they bunch up. Some of this tangled and downed corn is extremely hard to get into the combine.”

When corn headers become plugged with cornstalks that refuse to enter the machine, farmers must stop, shut down and remove the stalks by hand. “Sometimes you can only travel in one direction through the field to get the stalks picked up by the combine,” says Denny Friest, farming in southern Hardin County. “It’s taking us twice as long as normal to harvest these fields, and yields are often less than half of what we normally get. And we’re not in the worst area of the state for where the derecho hit the hardest.”

A crop insurance adjuster earlier this fall told Friest and son Brent they could disk under their hardest-hit acres. But they decided to go ahead and try to harvest the fields, even if it costs them more than it would net in revenue. They expect to get a decent crop from about a third of their 1,600 acres of corn. “We’ve got the good, the bad and the ugly,” Denny says.

Volunteer corn a concern

In eastern Iowa, Jim Swenson stopped combining downed corn in a Benton County field after he damaged his combine’s corn head. He ended up buying rolling cones and mounting them on the corn head to continue harvesting severely lodged corn. Swenson needs the grain to feed his hogs. He hopes to also sell some corn after harvesting enough this fall to meet his feed needs. “You salvage what you can from these damaged fields. You don’t make money from crop insurance,” he says.

Even if you choose to disk the fallen corn that isn’t harvested, that will cause problems as it spreads corn kernels and creates volunteer corn next spring.

“If you do tillage on the downed corn this fall, it is likely that a significant percentage of that corn seed will germinate this fall and then be winterkilled prior to spring,” says Iowa State University Extension weed management specialist Bob Hartzler. “However, in fields we’ve checked that have been tilled this fall, there were large numbers of partial corn ears still on the soil surface. It is likely these seeds will overwinter more successfully than the corn seeds in the soil profile. These ears will be a major contributor to volunteer corn populations next spring. Despite the large amount of corn germination in damaged fields this fall, volunteer corn will still be a significant problem in these fields next spring.”

Hartzler advises the downed cornfields, if they are corn-on-corn, be planted to soybeans next spring. The herbicide options available for soybeans provide better control of volunteer corn.

Another potential problem is mold growing on corn ears. Grain elevators and ethanol plants are testing corn samples and watching for aflatoxin in grain coming from downed corn. It’s easier for mold to form on ears when stalks are laying on the ground. Certain types of mold can produce mycotoxins such as aflatoxin. Fortunately, aflatoxin hasn’t shown up as a problem yet, probably because of Iowa’s ongoing drought, Naig says. 

Yield adjusted downward

USDA’s monthly crop report issued Oct. 9 estimates Iowa farmers will harvest 12.7 million acres of corn this fall. In August, the survey showed Iowa was expected to harvest nearly 13.6 million acres. USDA now estimates Iowa’s average corn yield will drop to 186 bushels per acre, down from forecasts of 191 bushels per acre in September and 202 bushels per acre in August.

Iowa farmers are expected to harvest 9.3 million acres of soybeans this fall, according to the October report, unchanged from September. USDA raised its estimate of Iowa’s average soybean yield to 56 bushels per acre, up 2 bushels from the September projection.

Even with fewer acres, Iowa farmers are still producing the most corn in the nation this year, harvesting an estimated 2.4 billion bushels. The state with the nation’s second-largest corn crop is Illinois at 2.2 billion bushels. Iowa soybean growers are producing 521.9 million bushels this year, second only to Illinois, which USDA says is harvesting 615 million bushels.

Estimated production declines

Nationally, USDA on Oct. 9 reduced its estimate of the number of corn acres that will be harvested this fall by nearly 1 million and reduced the number of soybean acres by 731,000. Thus, USDA’s forecast for U.S. corn and soybean production both fell about 1% from September. Corn production in the U.S. is projected to reach 14.7 billion bushels, soybeans nearly 4.3 billion bushels.

Reflecting the downward adjustments, corn and soybean prices have climbed. After the USDA report was issued Oct. 9, corn for October delivery closed up 8 cents at  $3.95 a bushel; soybeans rose 16 cents to $10.66 a bushel.

“USDA’s World Supply and Demand Estimates also released on Oct. 9 show the demand for corn has declined but production has also fallen,” notes Chad Hart, ISU Extension grain marketing economist. “While demand for soybeans is higher, soybean production has declined.”