The derecho storm on Aug. 10 left fields with varying degrees of downed corn. In the weeks following the storm, the condition of the corn plants has worsened, and the quality of the corn grain appears to be deteriorating. This deterioration in quality is expected to increase with time.
The quality of corn grain at harvest will determine whether a buyer exists in the market for your corn and the value of the grain. Do not settle insurance claims before you have the final word on value from the buyer. A projected 100-bushel-per-acre yield today with no one to accept that corn at harvest later is still a zero-value yield, plus unnecessary harvest expense.
Follow these guidelines on how to sample downed corn to check it for damage and other quality issues prior to harvest.
Know the quality of your grain
First step is to determine the grain quality for settlement just before harvesting the whole field. Quality of corn grain at harvest can be measured by obtaining a representative sample from strips or other representative portions of the field. There are standard adjustment procedures for identifying representative strips.
You can obtain a tank sample (field pass) by running the combine in these areas. This will also help you to get an idea of how well the mechanical harvesting will occur should you decide to harvest the whole field. Both the producer and the insurance adjuster need to agree that the sample is representative of the area to be adjusted. While ear samples are useful for in-field scouting to estimate quality, grabbing a few corn ears from different parts of the field is not a representative sample for pricing and adjustment purposes. Buyers purchase corn grain by the truckload and not by individual ears.
Representative samples of damaged grain, as agreed between the producer and adjuster, are best submitted to an Official USDA Grader where the full grade and toxins can be determined as a submitted sample. Federal Grain Inspection Service testing is normally more accurate than the rapid tests at grain elevators and provides better information for the buyer as well.
Make sure you have a buyer
Once the buyer agrees to accept the grain, based on the results of the submitted sample, the entire field then can be harvested without the burden of having to find a buyer for it. Before submitting the entire sample to the official grader, it may be helpful to test for moisture and test weight with the local elevator.
A test weight of 45 pounds per bushel or less represents potential grain quality issues and is a simpler test than getting a test for mycotoxins and total damage analysis done. Wet mills and dry mills, where corn is used in food products, may even have a higher test weight cutoff.
Checking the corn grain for bright yellowish-green florescence under a black light has sometimes been used to indicate the possibility of fungus growth, which may result in aflatoxin production. BGYF does not indicate the possibility of other mycotoxins nor a quantification of total toxins in grain. The BGYF test is a quick test and requires very little equipment, but is only to be used as an indicator for the presence of aflatoxin. When aflatoxin is possible, this test has value as a rapid screening for whether more detailed testing should be done.
Getting corn grain tested
Once the test results are back on the submitted sample and harvest of the field begins, it is normally impractical to test each truckload for toxins. Elevators and processors may decide to use a periodic composite sample (10 pounds or more from a series of trucks) to prove that the average concentrations of toxins in corn received is below limits.
Such samples can be submitted to a federal grader for toxins, while the in-house (grain elevator) graders can check for other factors. Or the sample can be used to check the in-house graders on all the quality factors being tested. Composite samples do not identify individual problem loads; more intensive sampling is needed if the composite samples test above market limits for that grain buyer.
Communication is important in the process as downed corn is harvested. All involved parties need to agree on the part of the field that is representative of the downed corn; how well the sample to be submitted for testing represents the field in question; and how the test results obtained are representative of the conditions in the field.
Good communication, along with proper sampling and testing of the corn grain before harvesting the whole field, can save a lot of time and energy. And it can help in decision-making if no buyer exists for the quality shown in the test results. A discussion of harvesting, testing, and storing the 2020 crop is available at 2020 Drought and Derecho Impacted Corn-Harvest, Mycotoxin Testing and Storage.
Hurburgh is an Iowa State University grain quality specialist and director of the Iowa Grain Quality Initiative at ISU.