2016 Harvest Grain Quality Update

October 19, 2016
ICM News

Iowa has had relief from the constant, late-September rains that were setting up for a difficult harvest season. As a result, the average grain moisture has fallen to a more typical 18-21%; lower in areas of lesser rainfall and vice versa. The potential for field drydown normally declines rapidly after mid-October. The issues of field mold that we reported in late September remain but shouldn’t be intensifying. Overall, the storage properties of 2016 will be average or below average, especially in wetter areas.

Grain storage

Attention should now turn to grain storage. The primary need is to cool grain that was either warm from the field or from drying. Air conditions normally allow grain to cool into the 40s in October and the 30s or below in November. The storage time chart  demonstrates the gain in storage time as grain is cooled into the 30s and 40s.

With less-than-ideal cooling conditions, there is undoubtedly a considerable amount of stored grain at temperatures in the 60s and 70s. Dewpoint is a rough measure of the lowest possible temperature to which grain can be cooled at a particular time.  In central Iowa, there have only been five days in September and October with average dewpoints below 45F. Dryers and storage bins simply have not been able to get grain cool to this point.  

The 8-14 day outlook is for higher than normal temperatures and above normal rainfall, which is not favorable for reducing stored grain temperatures into the 40s or below. Bins with lower airflow rates will be at most risk; it takes about 150 hours for 0.1 cfm/bu (a typical airflow rate in bins and other large storages) to reduce grain temperature. Drying and high air flow grain bins can take advantage of shorter periods of favorable cooling.

The large corn and soybean crop is causing grain elevators to make temporary outdoor piles, in addition to the tarped and aerated circular stadiums that have become commonplace for winter storage. Uncovered piles often do not have aeration fans which means that the grain temperature is essentially fixed at the temperature when the pile was made. These are high-risk situations this year. The large U.S. export commitments in the fourth quarter of 2016 will help to move out piled grain.

Mycotoxins and moldy fields

There have been scattered reports of several mycotoxins this year, as expected with warm and wet conditions. Any corn that is visibly moldy in the field should be tested before use. Buyers receiving corn from wetter areas are periodically monitoring samples to verify that none of the major mycotoxins are above allowable levels for use. While grain that was submerged by river or stream flooding is prevented by FDA from entering market channels, grain in potholes and low-lying fields can be marketed. The latter case still carries mold and mycotoxin risk and should still be tested before use.

Corn and soybean test weights

In overall quality, corn and soybean test weights are average. Protein content of corn is slightly below average, and starch content is slightly above average. Soybean protein and oil are good, approximately 35% protein and 19% oil, except in areas that had extreme September rains which halted crop development at the expense of protein content. Stalk and ear rot is creating more foreign material in corn, so it will be important to remove the center core after filling bins. In summary, cooling is the most important grain quality issue at this time. Pay attention to weather conditions for any opportunities to get grain into the 40s by the end of October.

Related articles:
Wet Weather Creates Challenges for Harvest
Consider Combine Adjustment for Wet Field Conditions
Scout Now for Ear Rots


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Charles Hurburgh Professor, Agricultural and Biosystems Engineering

Dr. Charles R. Hurburgh, Charlie to most everyone, is a native Iowan from Rockwell City (Iowa, USA). He continues to operate the family farm, and is a professor of Agricultural and Biosystems Engineering at Iowa State University. He has a bachelor's degree, master's degree, and doctoral degree fr...