When the calendar flipped from October to November the weather changed in a big way. Over the next 10 days, temperature predictions are highs in the 40’s and lows in the 20’s. These conditions make it much more difficult to field dry corn creating a need to send high moisture corn to the dryer. Currently only 37% of the corn crop has been harvested compared to a 5 year average of 56% Using a dry down calculator from Iowa State (https://crops.extension.iastate.edu/facts/corn-drydown-calculator), we can estimate how quickly corn will dry in the field. Based on the forecast, if your corn is at 30% moisture now, in 10 days it will be about 25% moisture and by the end of the month it may reach 21%. If our current moisture is 25%, in 10 days it will be about 22% moisture and by the end of the month it may reach 20%. When looking at these numbers, it seems like corn is field drying well. However, if we look at the forecast for corn at 20% now, the calculator predicts a moisture loss of less than half a point over the next 10 days and less than a point by the end of the month. Keep in mind, these are median predictions and if the weather model changes, we could see more-or-less field dry down.
As the weather turns cooler, it can become much more difficult to manage wet grain. It also becomes more difficult to determine moisture since most moisture meters are not accurate when grain temperature falls below 40 F. In order to get an accurate moisture estimate, put a grain sample in a sealed container and let it warm to room temperature and retest moisture. It is also recommended that you allow the corn coming out of the drier to cool to room temperature before testing moisture, especially if the tester is kept in a cool area. Also, keep in mind that you may need to adjust harvest logistics to account for longer transport times since corn above 28% moisture may freeze together and corn between 24-27% moisture often binds and will not flow properly from wet storage bins and trucks.
Now comes the challenges of drying high moisture corn in high temperature dryers. The high moisture corn will spend more time in the dryer, increasing its chances of browning. The high temperature air over a longer period during fast drying and cooling often creates stress cracks and broken kernels leading to a lower test weight and issues with storage. Most high temperature dryers are run at about 210 F. One way to reduce kernel damage in wet grain is to decrease the temperature below 200 F even though it will take longer to dry. Unfortunately, lower temperatures are not as efficient at drying. It takes 4,000 BTU to remove a pound of water at 150 F but only 2800 BTU at 200 F. Keeping dryer plenum temperatures as high as possible without damaging grain is ideal. Monitor the grain coming from the dryer for cracks and decrease temperatures until quality is maintained. As temperatures decrease below 40 F, the chances of condensation forming when hot grain is put into storage bins increases. Grain coming out of a high temperature dryer should be at 90-100 F to reduce the condensation potential. If your bins have large enough aeration fans, cooling the rest of the way in bin can also help improve grain quality. When hot grain is fully cooled to 30 or 40 F, the amount of stress cracks increases. During cooler temperatures it is even more important that the corn is cooled at its fill rate or faster. It takes an air flow rate of 12 cfm per bushel coming into the bin in an hour to keep up with cooling.
Increased dryer condensation can also cause issues. As the condensation cools during freezing night time temperatures, vents may become iced over decreasing efficacy and causing damage. If you are using a dryer bin, these vents freezing over could cause roof damage. To avoid this, leave all access doors open or close with an elastic strap that can act as a pressure relief.
If your corn crop was frost killed, another layer of challenges has been added. When corn is frost injured, a moisture tester will often read lower than actual grain moisture. The outer portion of the kernel dries faster than the interior. This grain is usually 1-2% wetter, even after drying than your moisture tester reads. In order to handle this, grain needs dried to 12-13% and fully cooled. It also takes more energy per percent moisture to dry this grain. Frost killed corn will have a lower test weight decreasing storage life.
Across the Midwest, more corn has been coming off wet using high quantities of propane and starting to cause shortages in some areas. While there is not a lot you can do about the supply side, you could contact your propane supplier about how much more gas you may need this fall. While each drier and temperature has a different efficacy, a common estimate is that is takes 0.02 gallons of propane to remove 1% point from a bushel of grain. If your corn is averaging 25% at harvest, you will need to remove 9.5% to dry it to 15.5% taking 0.19 gallons of propane per bushel or 190 gallons per 1000 bushels.
Even after drying, high moisture corn often has more fines due to more aggressive shelling and drying. These fines increase storage issues leading to corn going out of condition sooner. The fines can fill in voids deceasing airflow, causing hot spots and increased potential for insect damage. These fines can cause issues in the dryer leading to a greater potential for dryer fires. This can be managed in a couple ways. Fines produced in the combine can be removed using a drum grain cleaner before the grain enters the dryer. The high moisture corn is often much more fragile after drying so even if combine fines are removed, there is still a major concern for in bin fines. The first step to protecting damaged grain from insects is to cool it below 20-25 F, for most insects. Make sure the grain is cooled throughout by taking temperatures 12 inches into the grain at the top from multiple areas of the bin. After cooling bins, they should be cored to remove fines that accumulated in the center of the bin. During coring, about half of the peak in the bin should be removed creating a cone. If a cone is not created, the grain is bridging, and you should NOT ENTER the bin. If you have multiple bins, it is recommended that you sell the corn that was dried from the highest moisture first.
For the producers who use natural air drying, this will be much more complicated as air temperatures fall below 40 F. When temperatures are in the 30 to 40 F range, it will take over 2 months for this corn to dry in the field. In bin drying should not be attempted if corn is over 20% moisture. Below 20% moisture, the grain can be cooled to 20-30 F using aeration and left in the bin until spring temperatures are over 40 F and can be dried at that point. This grain should not be stored any longer than absolutely necessary after drying in the spring. Adding heat to natural drying bins can improve drying, but only slightly. The greatest improvement in natural drying time comes from increasing airflow. Adding heat can allow the final moisture of corn to improve on average due to higher relative humidity. If you can naturally dry corn in the winter it is only to about 16%.
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