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Grain drying basics

By Staff | Oct 11, 2019



More than likely if you own a grain drying system or even a bin with a fan, you are going to be utilizing them this year.

Kris Kohl, agricultural engineering specialist for Iowa State University Extension and Outreach said the first step to successfully drying corn is to be sure the bins have been properly cleaned out and maintained.

“Make sure there are at least six inches of space between the drying floor and the fines that have fallen through, otherwise, they need to get in there and vac them all out and that time is now to get that done,” he said. “They need to make sure all of the belts are tight, the bearings are greased and turn it all on make sure the rodents haven’t chewed through anything.”

Kohl said he advises producers to also clean out around the edges and add rodent control around the bin to try to keep their populations down as much as possible.

“Those would be the main things, also, check the seals around the vents so you don’t get rain dripping down into the grain,” he said.

Kohl said to remember there is quite a difference in the percentage of moisture in hand harvested corn versus machine harvested corn.

“Especially if the grain is fairly wet in the 20s when you check the moisture it will be about three percent higher moisture content when machine harvested versus hand harvested,” he said. “The kernels are soft and very easily tipped as the machine grinds them off of the cob and the very last thing that is made is down where the cob touches the end of the kernel on the germ and so it has a higher moisture content – that causes the moisture meters to pick that up and read high. If you are a grain merchandiser, you like that, because it’s really not that high, but it will read high. You put it on some heat, dry off that tip and it’s going to read a lot lower.”

If you are planning on drying your corn without heat and just a fan, Kohl said 20 percent moisture content is about the top end of what you can air dry in the bin.

“When they do that, they should only fill the bin half full and dry that before they start on the second half, which this could mean a lot of moving of augers and tractors, but this works very well,” he said.

Kohl said when we consider the weather we normally get during the fall, it is very good for drying corn down with a fan, but to keep in mind to never shut the fan off.

“Because, if you do, even if it is for one day because it’s raining and so forth, right where the moisture front is at in the grain bin you may get a line of mold that is about five to six inches wide,” he said. “Just leave the fans on and they will keep the grain cool and as soon as the dryer conditions come, it keeps on drying it and prevents it from overheating and molding by leaving it on.”

For those with a dryer system, Kohl said he would like to see the corn dry down to about 25 percent in the field.

“That’s because above that moisture content, the grain is so fragile. It kind of grinds up,” he said. “Our machines aren’t gentle enough to harvest grain wetter than 25 percent.”

If the corn doesn’t seem to dry down, Kohl said one option is to harvest it frozen.

“We are going to be harvesting 25 percent corn that is going to have to be dried and handled very carefully, or the guys are going to have to wait until it is field frozen corn. Field corn, combined after it is frozen does behave like dried corn until it thaws,” he said. “You can run fans at night when temperatures are below freezing and leave them off anytime temperatures are above that, but I am talking about being in December at this point.”

The good news is, Kohl said he believes most of the corn that is out in the fields is mature and earning its dry down time, but, unfortunately now that October is here, that will be a slow process and only get slower from there.

According to Kohl, typically October only delivers a two point per week dry down while November is one point per week and only one point per month in December.

How long can grain be stored?

Kohl said we have what is called an allowable storage time of grain and it changes with the moisture content and temperature.

“The real thing is temperature,” he said. “If it starts to get warm at all, that allowable storage time goes down very, very quickly. Say 90 degrees; it’s just about three days. What happens is, it doesn’t stay 90 degrees very long, it starts to heat up because the bacteria are eating on the tips and the corn will start to decompose really, really fast and it will heat up to 100 to 150 degrees overnight.”

What if you harvested wet grain and don’t have the ability to dry it down?

“That’s very dangerous because one or two days of it sitting in a grain wagon having the bacteria destroy it, will oftentimes use up half of the allowable storage time and will quickly,” he said. “Instead of a normal storage life, which 15 percent corn’s normal storage life is about 800 days, if you have 90 degree, 22 percent moisture corn, it will be three days. Then you will have bacteria that is going to want to come back and it will get hot spots in the problem areas all of the time.”

Kohl said a website that will help calculate how long it could take to dry corn down is available from the University of Minnesota at bbefans.cfans.umn.edu.

Drying corn definitely comes with a cost.

According to Paul Kassel. ISU Extension field agronomist, the cost to dry down 200 bushel per acre corn is $7.61 per point. This cost per acre assumes $0.0375/bushel/point commercial drying cost and 1.45 percent shrink per bushel.

The cost of LP gas to dry 200 bushel an acre corn is $4.40 per point. This assumes 0.02 gallon of LP to dry one bushel of corn, one point of moisture and $1.10 per gallon LP cost. This cost does not include the cost of electricity, or the fixed costs of drying equipment, grain handling equipment or storage structures.

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