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Published September 30, 2013, 11:15 AM

Moisture a problem for corn

Variability in moisture content and maturity will create corn drying and storage challenges this year, a North Dakota State University grain drying expert warns.

By: NDSU Extension Service,

Variability 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,” says Ken Hellevang, Extension Service agricultural engineer. “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 from 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 because of 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 because of 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.

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.

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 degrees, little drying may be possible during the fall using a natural-air system if the harvest is later in the fall.

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.