Ask the Doctor: Relative Humidity’s Importance in Winter
No matter how cold it is outside, mold can still occur if a grain’s moisture is too high, which can cause the relative humidity to create perfect conditions for mold. This means it can actually be safer to freeze your grain as it can prevent mold from growing, if grain was not able to be dried down before colder temperatures set in.
What steps should be taken to safely store corn harvested this late in the season?
When harvesting corn in late November or December it’s likely to have a high moisture content, around 20-22%. In this case, it is better to keep the corn frozen through the winter before drying it in spring. Although freezing the corn may present other issues, if you do not freeze high moisture corn and the corn temperature remains between 35oF and 40oF, you will end up getting blue eye mold.
This issue mostly occurs in the northern border states, particularly in operations not running fans in winter. The goal is to run your fans to freeze the grain without causing the formation of ice within the bin.
For customers that may have a true hotspot during winter months, with temperature below freezing, what are best practices to ensure grain safety and reduce the hotspot?
The main reason for any hotspot is due to the fact that the grain has relative humidity (RH) greater than 80%. Once above 80% RH, the tendency to lose grain due to mold is higher. If you are storing corn above 17-18% moisture, the relative humidity is greater than 80%. Regardless of how cold it is outside, even if the corn temperature is around the 35°F range, mold can grow if the RH is greater than 80%.
The best practice would be to dry the grain to below 65-70% RH to reduce mold activity. If drying is not an option, it is better to freeze the grain versus keeping it above freezing temperature. You may continue drying in spring.
What is your recommendation for target temperatures that should be set on AGI BinManager systems going into winter?
If the grain is already dried to a safe storage relative humidity (RH) of around 65-70%, the target grain temperature should be in the range of 35oF-40oF during winter. This is to avoid condensation and to not freeze the grain.
The safe storage RH varies across different hybrids of the same grain type. The most commonly used marketable safe storage moisture contents during winter in the mid-west regions are 15% for corn and 13% for soybeans. For southern states with higher ambient temperature, the safe storage moisture contents are 14% for corn and 11-12% for soybeans. As established in the above question, for an RH greater than 80%, it is better to freeze grain below 32oF and finish the drying process in spring.
For how to properly thaw grain after freezing it during winter, see our last Ask the Doctor Blog.
Dr. John had lots to say about relative humidity (RH) this month, for questions about relative humidity % values please contact customer support at 855-293-5607 or digital.support@aggrowth.com
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