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No real future in leaving corn stand in the fieldNo real future in leaving corn stand in the field

Once you get past Oct. 20 in Iowa, history shows corn doesn't dry down much more in the field

Rod Swoboda 1

October 20, 2016

5 Min Read

As farmers are moving through mid-October with the 2016 harvest, Iowa has had relief recently from the constant, late-September rains that were setting them up for a difficult corn and soybean harvesting season. As a result, the average grain moisture for corn coming out of the field as of October 15 to 20 has fallen to a more typical 18% to 21% moisture content; lower in areas of lesser rainfall and higher in areas of higher rainfall. 


So, should you leave your unharvested corn standing in the field a little longer to let it dry down naturally on the stalk, before you harvest it? To try to save some money on artificial drying costs such as propane and electricity? Or should you harvest your corn ASAP, to avoid the risk of field losses, especially if weather turns cold, wet or windy moving through the rest of October and into November?

Potential for corn grain to dry down in the field is diminishing
The potential for corn grain to dry down normally in the field declines rapidly after mid-October, says Charles Hurburgh, grain quality expert at Iowa State University. Plus, a lot of fields have cornstalk health problems. A big wind could come along and knock those weak stalks down; strong winds can flatten cornfields fast.

“There’s no real future in leaving the corn standing in the field now,” he says. “I advise going ahead and getting it harvested once we’re past October 20. And if you have to dry the corn in a grain dryer or a drying bin, spending the money to do that is ok. You’ll have the corn in the bin instead of running the risk of leaving yield in the field.”

On another topic, Wallaces Farmer asked Hurburgh, What’s happened with the moldy corn issues that confronted some farmers who had heavy rainfall in their area of the state as they started harvesting corn earlier this fall? Northeast and north-central Iowa fields were flooded in some areas in September.

“The issues of field mold that were reported in late September remain in Iowa today,” Hurburgh says. “But they shouldn’t be intensifying. I don’t look for field molds to become more prevalent this fall, as we move into the homestretch of harvest. Overall, the storage properties of 2016 grain harvested this fall will be average or below average in the bins, especially grain from fields in the wetter areas of the state.”

Grain storage considerations should now be your focus
Attention should now turn to managing grain in storage, advises Hurburgh. The primary need is to cool the grain that was either warm from the field or from drying—when it entered the bin. Air conditions normally allow grain to cool into the 40s in October and the 30s or below in November. The storage time chart  demonstrates the gain in the amount of storage time you get as grain is cooled into the 30s and 40s degree range.

With less-than-ideal cooling conditions, there is undoubtedly a considerable amount of stored grain at temperatures in the 60s and 70s. Dew point is a rough measure of the lowest possible temperature to which grain can be cooled at a particular time, explains Hurburgh. “In central Iowa, there have only been five days in September and October with average dew points below 45 degrees F,” he adds. “Dryers and storage bins simply have not been able to get grain cool to this point.”

Weather outlook for next two weeks doesn’t favor cooling stored grain
The eight to 14 day weather outlook as of October 19 is for higher-than-normal temperatures and above normal rainfall, which is not favorable for reducing stored grain temperatures into the 40s or below, says Hurburgh. 

Bins with lower airflow rates will be at most risk; it takes about 150 hours for 0.1 cfm/bu (a typical airflow rate in bins and other large storages) to reduce grain temperature, he notes. Drying the grain and use of high air flow grain bins can take advantage of shorter periods of favorable cooling.

Outdoor grain piles are high-risk situations this year
This fall’s large corn and soybean crop in Iowa is causing grain elevators to make temporary outdoor piles, in addition to the tarped and aerated circular stadiums that have become commonplace for winter corn storage. Uncovered piles often do not have aeration fans, which means that the grain temperature is essentially fixed at the temperature when the pile was made. “These piles of grain outdoors are high-risk situations this year,” notes Hurburgh. “However, the large U.S. export commitments in the fourth quarter of 2016 will help to move out the piled grain.”

Mycotoxins and moldy fields of corn and soybeans
There have been scattered reports of several mycotoxins this year in Iowa, as expected with warm and wet conditions for harvesting this fall. “Any corn that is visibly moldy in the field should be tested before use,” says Hurburgh. “Buyers receiving corn from wetter areas are periodically monitoring samples to verify that none of the major mycotoxins are above allowable levels for use.”

While grain that was submerged by river or stream flooding is prevented by FDA from entering market channels, grain in potholes and low-lying fields can be marketed. The latter case still carries mold and mycotoxin risk and should still be tested before use. Read this article “Management of Flood-Submerged Grains” for more information.

Corn and soybean test weights are about average this fall
In overall quality, corn and soybean test weights are average in Iowa this fall, says Hurburgh. Protein content of corn is slightly below average, and starch content is slightly above average. Soybean protein and oil are good, approximately 35% protein and 19% oil, except in areas that had extreme September rains which halted crop development at the expense of protein content. 

Stalk and ear rot is creating more foreign material in corn grain at harvest this year, so it will be important to remove the center core of grain after filling your storage bins, he says. “In summary, cooling is the most important grain quality issue at this time,” notes Hurburgh. “Pay attention to weather conditions for any opportunities to aerate and get stored grain into the 40 degree range by the end of October.”

About the Author(s)

Rod Swoboda 1

Editor, Wallaces Farmer

Rod, who has been a member of the editorial staff of Wallaces Farmer magazine since 1976, was appointed editor of the magazine in April 2003. He is widely recognized around the state, especially for his articles on crop production and soil conservation topics, and has won several writing awards, in addition to honors from farm, commodity and conservation organizations.

"As only the tenth person to hold the position of Wallaces Farmer editor in the past 100 years, I take seriously my responsibility to provide readers with timely articles useful to them in their farming operations," Rod says.

Raised on a farm that is still owned and operated by his family, Rod enjoys writing and interviewing farmers and others involved in agriculture, as well as planning and editing the magazine. You can also find Rod at other Farm Progress Company activities where he has responsibilities associated with the magazine, including hosting the Farm Progress Show, Farm Progress Hay Expo and the Iowa Master Farmer program.

A University of Illinois grad with a Bachelors of Science degree in agriculture (ag journalism major), Rod joined Wallaces Farmer after working several years in Washington D.C. as a writer for Farm Business Incorporated.

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