NDSU Extension Service, Published September 24 2013
Harvesting, drying, storing corn could be challengingVariability in moisture content and maturity will create corn drying and storage challenges this year, a North Dakota State University grain drying expert warns.
"There are variations within regions and even within fields due to availability of moisture," Extension Service agricultural engineer Ken Hellevang says. "Many fields have areas that are totally brown but also have areas that are still green and growing. In those green spots, test weights and moisture contents will be high, while in the brown spots, test weight will be lighter and moisture contents much lower."
Drought conditions stress the corn crop, leading to weak stalks and shanks. Weak stalks contribute to "downed" corn due to wind or other forces, and weak shanks contribute to "ear drop" and large field losses. Hellevang recommends checking the condition of the corn in the field and possibly harvesting early to minimize losses even though areas of the field may be at higher moisture contents.
Drought conditions also lead to larger than normal in-field corn moisture
content variations. Moisture content may range from 15 to 25 percent in the same field due to soil variations or other contributing factors.
Kernel moisture content, size and density or test weight likely will vary on an individual cob as well. Drought stress leads to small kernels on part of the cob and large kernels on other parts of the cob. Even the larger kernels may have a lower test weight due to the plant stress.
Corn moisture variation in a field means that adjusting the combine for
conditions will be difficult, and that may contribute to more fines in the corn. Also, more fines are produced when corn is wet because more aggressive shelling is required, which causes more kernel cracking and breaking.
In addition, immature corn contains more small and shriveled kernels. Fines
cause storage problems because they spoil faster than whole kernels, have high airflow resistance and accumulate in high concentrations under the fill hole unless a spreader or distributor is used. Preferably, the corn should be cleaned before binning to remove fine material, cob pieces and broken kernels.
Corn reaching maturity about Oct. 1 may be slow to dry due to cooler
temperatures. Standing corn in the field may dry about 1.5 to 3 percentage
points per week during October and 1 to 1.5 or less per week during November, assuming normal North Dakota weather conditions.
If corn has a moisture content of 35 percent on Oct. 1, it probably will dry to only about 25 percent moisture on Nov. 1, assuming normal North Dakota climatic conditions. Field drying normally is more economical until mid-October, and mechanical high-temperature drying normally is more economical after that.
If the moisture content varies in corn going into a high-temperature dryer, it also will vary coming out of the dryer, Hellevang says. For example, if the moisture ranges from 15 to 25 percent going into the dryer, it may range from 11 to 19 percent coming out. More mixing in the dryer will help reduce the moisture variation coming from the dryer. This moisture variation will affect storability and storage management greatly.
Operating an aeration fan will help move moisture from wet to drier kernels. Air going past wet kernels picks up moisture, and that moisture will transfer to drier kernels as the air goes past them. Moisture movement will be minimal without aeration airflow past the kernels. Run the fan longer than is required to cool the grain to even out the moisture content. The moisture may not equalize, but it will become more uniform. The moisture still may range from 14 to more than 16 percent.
Corn above 21 percent moisture should not be dried using natural-air and low-temperature drying to minimize corn spoilage during drying. Because the drying capacity is extremely poor at temperatures below 35 to 40 degrees, little drying may be possible during the fall using a natural-air system if the harvest is later in the fall.
Adding heat does not permit drying wetter corn and only slightly increases
drying speed. The primary effect of adding heat is to reduce the corn moisture content. Turn fans off during extended rain, fog or snow to minimize the amount of moisture moved into the bin by the fan.
Using the maximum drying temperature that will not damage the corn increases the dryer capacity and reduces energy consumption of a high-temperature dryer. Be aware that excessively high drying temperatures may result in a lower final test weight and increased breakage susceptibility. In addition, as the drying time increases, high-moisture corn becomes more susceptible to browning.
Grain segregates based on size and density as it flows into a bin or container. Generally, the smaller and denser material will accumulate in the center and the larger material flows to the perimeter of the bin. Therefore, areas of wet corn and variations in test weight are possible in a bin. Using a distributor or "coring" the bin may reduce the accumulation of smaller material in the center of the bin.
The storage life of stressed low-test-weight corn is expected to be shorter than normal, so farmers need to be more diligent with drying and storage management. Hellevang suggests drying low-test-weight and stressed corn a percentage lower in moisture content than normal because of greater variations of moisture content in the grain mass and increased kernel damage and broken cobs, which could magnify storage mold problems.
Corn with damage to the seed coat and immature corn has a shorter storage life than mature, good-quality corn. Therefore, cooling the grain in storage to about 20 to 25 degrees for winter storage in northern corn-growing regions and near freezing in warmer regions is more important than for mature, sound corn. Hellevang also recommends checking the stored grain more frequently and not putting immature or damaged corn in long-term storage.
Storage in a poly bag is a good temporary storage option, but it does not
prevent mold growth or insect infestations. At moisture contents exceeding about 25 percent, ensiling may occur at temperatures above freezing and prevent the corn from being dried and sold in the general market.
Select an elevated, well-drained location for the storage bags, and run the bags north and south so solar heating is similar on both sides of the bags. Wildlife can puncture the bags, creating an entrance for moisture and releasing the grain smell, which attracts more wildlife. Monitor the grain temperature at several locations in the bags.
For more information, do an Internet search for NDSU corn drying.