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It is recommended to dry corn at less than 50 degrees or above 120 degrees. Drying at temperatures in between those numbers will invite spoilage, according to Kris Kohl, Iowa State University Extension field engineer.

EMMETSBURG — With low prices and on-farm bins that await a new year’s crop, grain management will be as important as ever this year, according to one expert.

Kris Kohl, Iowa State University Extension field engineer, said natural corn dry-down can be estimated at four points per week during September, followed by two points per week in October, one point per week in November and one point per month during December.

Corn usually black layers at 30 percent moisture, he said.

“When you’re about 15 days away from black layer, the color on the shuck that’s holding the ear turns white,” said Kohl. “When you see that happen, the corn is sucking all the nutrients out of that ear sheath and … translocating (them) into the kernel itself. It’s getting ready to shut down.”

Soybean in-field dry-down is fairly fast, he added, because it’s an oilseed. Soybeans can grow from 15 percent in the morning to 10 percent late in the afternoon.

But he gets more questions about how wet soybeans can be harvested.

“I recommend not going any higher than 16 percent,” he said. “If you go much above that, they don’t shell out very well and they will turn to mush in the combine.”

Kohl added soybeans that flatten out a little — resembling lima beans — are at about 22 percent moisture. Too many of them in a load will create pockets of wet grain that accumulate in the center of the bin, which can cause problems such as fines falling into the wet beans and plugging up all the holes so air can no longer circulate throughout that area, and creating a peak in the center of the bin, where air is less likely to reach — especially with fines plugging air holes.

A power spreader in the bin can help, but any time grain goes into a bin with uneven moisture levels, they tend to sift differently when put into the bin.

Kohl said high moisture soybeans can be stored for about 30 days before they will start to spoil, with temperature highs in the 50s and lows in the 40s. He recommended at least a 10-horsepower fan to dry grain the most efficiently in the time producers have to dry grain down enough to store.

Drying with heat will speed the drying process, but 20 degrees is the highest increase in temperature recommended. Kohl said he makes that recommendation when temperatures are below freezing.

For those drying in that fashion, if they go deeper than 4 or 5 feet, Kohl said they should consider stirration to break up soybeans, especially so they don’t set up and get hard.

Since soybeans are oilseeds, he encourages producers to try to dry their soybeans naturally as much as possible rather than use dryers because of the dangers of fire associated with oilseed grains and combustion from grain dryers.

“If a combustion fire in the dryer burns one kernel of corn, it’s not a big deal,” he said. “But if it burns one bean, each bean has enough energy to burn 10 more beans, and those 10 beans will each burn 10 more beans. You’ve got a real problem, so make sure everything is clean and there are no corn stalks or weeds or other things that can catch on fire. The safest thing is to use natural air to prevent the high risk of fire.”

As corn goes, Kohl said there are drying issues nine years out of 10, but with soybeans that decreases to about three years out of 10.

Maximum storage life for corn at 15.5 percent moisture at 40 degrees is 1,012 days; that same percent moisture stored at 50 degrees will keep corn safe for 450 days; at 60 degrees it lowers to 197 days, and at 70 degrees it will last 109 days.

“When you have exceeded 63 (storage) days at 20 percent moisture, that has dropped the grade to No. 3 corn, and the corn will have a musty odor, and often times will have a physical mold present,” said Kohl. “We recommend that when you sell corn, you should have used up half of the useable storage life yourself, and you should give half to the next (entity) who has purchased it from you.”

He added corn frozen in the field and harvested will store better than corn that freezes while it is in the bin, mostly because corn frozen in the field will come into the bin with air around each kernel, unlike corn that freezes after it is in the bin.

Corn held before going into the dryer would need a minimum of 1/10 cfm/bu to keep it cool.

“With that, there is enough air flow that it will cool the temperature down to the dew point temperature,” said Kohl. “Dew point temperature normally is about what the low temperature is of the day. If you are aerating anything you can cool it to the low temperature of the day.”

He went on to say that fall conditions are good for drying corn naturally. For specific numbers, 1.25 cfm/bu on the bushels in the bin will dry about five to eight bushel points per 1,000 cfm/hour, and they get about 1,000 cfm for each horsepower.

Bushel points are the number of moisture points above dry grain times the bushels in the bin. For example, in a 10,000 bushel bin of 16 percent corn 1 point above dry, there are (16-15) x 10,000 = 10,000 bushel points to be removed. If the corn is at 20 percent, then there are ( 20-15) x 10,000 = 50,000 bushel points to be removed.

To calculate daily drying capacity, Kohl said it depends on the outside temperature. If the high is 80 degrees, moisture would drop eight points per hour per horsepower. The numbers correlate similarly — 70 degrees drops moisture seven bushel points per hour per horsepower, and similarly for 60 degrees, 50 degrees, 40 degrees and so on.

“Because of the way corn dries … it completely dries out those kernels on the bottom,” said Kohl. “The one on the top stays as wet as the day you put it in until a drying front comes through. The kernels on top still might seem wet, but you have made progress.”

He recommends drying corn at less than 50 degrees or above 120 degrees. Anything between those numbers will invite spoilage. A drying front will be about 12 to 18 inches thick and will be completely dry below and completely wet above. For natural air drying after freeze-up, Kohl recommends drying in the spring.

Additional suggestions include cooling the corn below 30 degrees and checking corn bi-weekly until the temperature is warm enough to dry it. He added that if moisture on top is above 18 percent, producers should start by March 15. If moisture on top is below 17 percent they should start by April 1.

For high-temperature drying, Kohl said grain must be stirred if it’s more than 4 feet deep, and it should be dried at 120 degrees or more. It will remove 50 bushel points per horsepower per hour at 120 degrees, and it will remove 80 bushel points per horsepower per hour at 160 degrees.

For maximum corn storage, Kohl said to cool it to below 40 degrees, check corn bi-weekly until May, and warm corn before selling it to prevent false high moisture readings if the corn temperature is below the dew point.

ISU Extension and Outreach has charts to help producers calculate drying rates and capacities. They can be found at extension.iastate.edu. Producers can also download a web app from the University of Minnesota to help them with grain drying questions, which can be found at webapps.bbe.umn.edu/fans.