Grain Quality Considerations After Derecho and Drought

August 31, 2020 2:45 PM
Blog Post

The combination of drought, derecho and recent hot weather in Iowa increases the need to keep grain quality in check. As harvest nears, consider the following:

  • Maintain contact with your crop insurance adjuster. We recommend having a conversation about how grain quality will be handled in your individual policy. It's important to ask about the specific quality factors (test weight, damage) and feed safety factors (mycotoxins) that will be considered.
    • Quality has to be crop-adjusted in the field, or by sample at harvest before storage.
    • In drought areas, the biggest concern will be field molds, especially the mustard green aspergillus flavus fungus that produces aflatoxin. This will show up primarily after maturity, from about 30% moisture down through 18%.  
    • In downed corn areas, corn maturity was halted abruptly which will cause low test weight, very soft kernels, likely low protein, and very short storage life. Expect mold growth on downed corn, with several toxin potentials. Corn below 45 lb/bu test weight should not go into general commerce without knowing its intended use and impacts on that use.
  • Call your elevator to ask how or if different qualities of grain will be accepted. Ask them what factors they will look at and if there will be acceptance limits.
    • Evaluate your fields by harvesting small areas of each so that samples can be taken to an elevator or possibly third party graders, before truckload lots are harvested. 
    • Work with the elevator and crop adjuster to identify the feasibility of harvest to alternate markets versus destruction. Expect that processors (feed mills, ethanol producers, wet millers, dry millers) will not accept very light or visibly mold damaged corn. All processors are negatively affected in one way or another. Grain elevators may have rejection policies based on their subsequent markets.
  • Continue to scout grain in the field for quality issues (primarily mold development). Continue reporting what you find to your crop adjuster, even if there has been one visit for quantity loss determination. This could change acceptance, use and valuation. Again, ask about special markets for severely damaged corn and about the process for zero valuing if quality continues to deteriorate before harvest.
    • Check strips are prone to quality loss if not samples just before harvest (or at harvest).  At-harvest tank samples are preferred because it is easier to obtain the 10+ pound sample required for accurate toxin testing.
    • If check strips are left and harvested after the field, be sure that the results won’t be poor quality enough to have zero value in the intended market. You may be left with harvested grain that you cannot use, or that will be rejected by buyers.
    • Quality issues from drought or storm damaged corn can become worse in storage; quality changes in storage are not covered by crop insurance. Mycotoxin levels typically do not increase in storage if the corn is dried quickly after harvest to below 15% moisture, cooled immediately and managed by normal best practices for aeration, center core removal and temperature monitoring.
  • Test the grain being fed to livestock. The key factors to consider are test weight, protein and mycotoxins. A veterinarian can access testing from ISU on these factors and help interpret data.
    • Ration mixes may need to be adjusted for composition.
    • Smaller animals may have issues with consumption of feed made from low test weight (low density) grain.
    • All mycotoxins have guidance levels for the maximum content of each mycotoxin by species.

Additional Resources:

Keep in touch with ISU Extension and Outreach for timely updates. Field trials are underway for harvest options, cover crop options and updates are forthcoming on market considerations.

For specific information on grain quality,  storage, and testing, visit the Iowa Grain Quality Initiative website.

iowa drought map
Most recent drought conditions in Iowa. Courtesy of the United State Drought Monitor.

downed corn field
Downed corn field due to dercho in Iowa. Image courtesy of Meaghan Anderson.



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...