- Corn harvest typically starts well before 15% moisture to spread out workload and reduce risk.
- There are additional costs with drying corn, but the benefits may be worth the extra expenses.
- Regardless of the way the corn is dried, corn is delivered at 15% moisture or less to avoid dockage at delivery and in-bin spoilage.
Harvest is around the corner for the Midwest with harvest already occurring in other parts on the United States. This time of year always has growers thinking about when to start shelling corn and what moisture they should get rolling in the field. Most will choose to start well before corn dries to 15% to spread out workload, reduce risk of late season wind events that lodge corn, reduce harvest loses, and fill early fall corn contracts.
There is quite a bit of corn that will probably black layer in the next couple of weeks and corn moisture will be between 30-35%. Once black layer occurs, you can expect 0.5-0.75% moisture reduction per day when the weather is warm, sunny, and a slight breeze; that dry down reduces to 0.25-0.5% per day when we reach October, and almost no reduction in moisture from November on.
In addition to in-field drying, a grower may choose to use natural air drying via bin fans. There are multiple factors in determining how well or how much energy will be used during the drying process. When choosing natural air drying with bin fans, note that moisture in the low 20% levels in the wettest corn we can typically dry with air alone without spoilage. Cost to dry corn is highly variable based on ambient air temperature, but ranges from 0.5-1.25 kWh/bu (Wilcke 2018).
If utilizing heat to dry corn, there are a couple of other considerations to consider. Drying corn utilizing a source such as propane does add cost to the operation. A general rule of thumb is that it takes 0.02 gallons of propane per bushel to remove 1% moisture in the corn. To calculate cost per bushel to dry only factoring the fuel used, you should take 0.02 X moisture removed X price of propane. If we want to dry down 20% corn to 15% and the price of propane is $1.75, the results are: 0.02 x 5 x 1.75=0.175. This means the cost of propane to dry 20% corn to 15% is 17.5 cents per bushel. This is a very rough guide as dryer type, dryer efficiency, plenum temperature setting, and ambient temperature all influence energy required to dry corn. The higher the temperature for a long length of time can increase corn cracking, which is undesirable. When using heat to dry corn, it is very important to cool the corn back down shortly after the heat is removed.
Regardless of the method used to remove moisture, we should strive to store corn at less than 15% for short term storage (3-6 month) to reduce spoilage or dockage during delivery. For longer term storage, corn moisture should be reduced to 13-13.5% moisture to avoid issues.
Sources
Wilcke, W. 2018. “Energy Costs for Corn Drying and Storage.” University of Minnesota Extension. https://extension.umn.edu/corn-harvest/energy-costs-corn-drying-and-cooling.