By ROD SWOBODA
It’s been a long but pretty good harvest in Iowa. The biggest concern is that corn came out of the field this fall at a wetter-than-normal grain moisture content. And with a big crop and low prices, farmers are storing it in hope of capturing better prices later, which may take awhile. “A lot of this year’s corn and soybeans will likely be stored a long time, longer than usual,” predicts Charlie Hurburgh, a grain quality expert and director of the Iowa Grain Quality Initiative at Iowa State University.
As harvest was finishing up in November, corn was still coming out of the field at 18% to 20% moisture. Because cooler-than-normal temperatures and damp air delayed drydown earlier this fall, a large amount of corn was harvested at even higher grain moisture content.
Corn can be safely stored for six months with moisture content of 15% and up to a year or more at 14%, if properly cooled down and aerated after drying. Hurburgh has heard of several situations in Iowa where this year’s grain has already gone out of condition. Corn moisture being a little higher than normal this fall is a factor.
“You need to provide enough aeration to take care of the moisture content of the grain,” advises Hurburgh. “For corn with an 18% to 20% moisture content, the aeration rate would need to be one-half to 1 cubic foot per minute per bushel. In other words, a strong movement of air through the grain is needed if you expect wet corn in the 18% to 20% moisture range to stay in good condition while you hold it, prior to drying it to a safe level for storage.”
Test weight is one of two reliable indicators of corn storability. The other is variation in grain moisture at harvest. Grain with a high test weight stores well. Corn that’s 57 to 60 pounds per bushel will store from 25% to 50% longer at the same moisture content and temperature than 54- to 56-pound test weight corn.
Store best grain first
What advice does Hurburgh give farmers who intend to hold stored corn and soybeans longer than usual? “Do some good planning as to which bins of corn and soybeans you intend to hold into August 2015 or beyond,” he says. “Choose your highest test weight grain for the longer-term storage. And put it in your better storage bins — those bins with the better aeration distribution system.”
Following the basic principles of good stored grain management is important. Immediately after harvest and drying, aerate grain to cool it down. “Shelf life begins to go down right away,” says Hurburgh. He offers these guidelines to prevent grain from spoiling in the bin:
• Provide adequate aeration (0.1 cubic foot of air per minute or more, per bushel). All bins with all grains — soybeans as well as corn — should be aerated.
• Run a cooling cycle at every 10- to 15-degree average change in outside temperature, starting at harvest. With 0.1 cfm per bushel, a cooling cycle will take about 150 hours to move completely through the grain mass; it will take proportionately less time with higher airflows.
• Get the grain below 40 degrees F as quickly as possible. Keep repeating the aeration cycle as outdoor air temperature drops by 10 to 15 degrees until you eventually get the grain cooled down to 40 degrees or below. However, you don’t want to freeze the grain. Don’t aerate when outdoor air temperature is below 32 degrees.
• Remove the center core of fines after you fill a bin with grain. Variable quality and lower test weight grain will have more fines.
• Inspect grain and monitor its temperature weekly until December, and every two weeks thereafter. Automated temperature cable systems are very useful; the larger the bin, the less likely a manual check will be adequate.
• Responding to temperature change is as important as the actual temperature. A 3- to 5-degree change between readings, even if from 40 to 50 degrees F, is indicative of spoilage if the fan has not been run in the interim.
• Stay within the grain temperature-moisture guidelines listed in the table found on the previous page.
Quality of 2014 crop
Although many acres of corn and soybeans were planted a little later than normal or were replanted late in the spring due to wet weather, and maturity came after the prime drying weather, grain quality hasn’t been much of a problem this fall in Iowa. The quality of this year’s crops, both corn and soybeans, is generally good.
Corn test weight in 2014 has been a little less than the past two years, but it’s still well within the “No. 2 yellow” range of 54 to 56 pounds per bushel. Keep in mind that a slightly lighter-than-normal test weight will shorten the storage life of corn in the bin. “That’s why you should put your highest test weight grain in bins where you can hold grain to sell it next summer or beyond,” says Hurburgh. “It’s always a challenge to get through the hot summer weather without some grain storage problems.”
Normal test weight is 56 pounds per bushel. This year’s crop has produced a lot of corn that is higher, in the 57- to 60-pound range. That’s the corn you want to put into long-term storage. “This year’s higher test weight corn gives you an opportunity to choose where to store corn, which bins to put it in,” says Hurburgh. “August and September of next year is when the real issues of stored grain going out of condition will likely show up.”
Monitor alternative storage, too
This fall’s huge corn and soybean crops filled the bins, and many farmers and elevators have had to use alternative storage for the rest of the crop. Corn piles are appearing outside in some areas of Iowa. Some corn is also being temporarily stored in machine sheds. Grain piled outside and in buildings needs to be checked regularly for signs of spoilage.
Piling corn in a shed, under roof, will work if it’s piled over a fan and ductwork system to provide aeration, says ISU grain quality specialist Charlie Hurburgh. Piling corn outside is riskier. Generally, if grain must be piled outdoors, it is best done at a commercial elevator, where it can be monitored and the quality controlled more easily than corn piled on a farm.
Some farmers have put corn in big plastic grain storage bags this year. Moisture is the mortal enemy of stored crops. Although the silo bags are sealed, they can leak, especially if there are tears or punctures in the plastic, or if the bags are placed on wet ground. Also, the same as with bins, make sure the grain is dry before storing it in a bag. The key to use bags successfully is to get grain as dry as possible before storing it. Hurburgh recommends drying corn to moisture content of 15% or lower before bagging. Don’t put wetter corn right out of the field in bags.
Check the moisture of bagged grain regularly, he adds, especially if weather turns rainy or snowy, or there are long warm spells. The big bags aren’t ventilated, which means there’s no way to circulate air inside them to prevent moisture buildup in grain. The only way to test the grain for moisture once corn is in the bag is to put a small hole in the cover, extract a grain sample and reseal the bag using adhesive tape. A special adhesive tape from the bag manufacturer works best.
Training modules address storage
Crop producers are faced with new grain storage issues as they store increasing amounts of grain for local processing, sometimes storing grain for a full year or longer. A team of ISU Extension specialists, as part of the Iowa Grain Quality Initiative, is working to meet the information needs farmers and elevators have related to grain storage. The team has produced three Web-based training modules covering key aspects of drying and storage. Greg Brenneman and Shawn Shouse, ISU ag engineering specialists, are the online course instructors. The 20-minute modules cover:
• aeration of stored grain
• energy efficiency and drying capacity gains from dryeration
• fan performance and sizing
They can be viewed or downloaded at www.extension.iastate.edu/grain/topics/grainstorage.htm.
This article published in the December, 2014 edition of WALLACES FARMER.
All rights reserved. Copyright Farm Progress Cos. 2014.