The 2009 Corn CropA Year to Recognize Quality

By Charles R. Hurburgh | June 10, 2010
The 2009 U.S. corn crop demonstrated clearly, and in many cases painfully, the connection between ethanol plant performance and raw corn. The crop lagged in development as the growing season progressed last year even though fields looked healthy. By Sept. 1, heat accumulation was 20-25 percent below normal in the Corn Belt although localized warm spots in late August and September prevented worse problems. Average harvest moistures ranged from 22-24 percent in the central and western Corn Belt to the upper 20s and lower 30s in the north and east. Test weights ranged between 50-52 pounds per bushela good indicator of kernel development and storability.

Cool wet conditions promote the growth of fusarium, gibberella and cladosporium fungi. The first two produce the toxins fumonisin, vomitoxin and zearalenone, but not aflatoxin, which generally occurs in hot, dry conditions. Vomitoxin and zearalenone were the most prevalent in 2009, for which the Food and Drug Administration guidelines (not action level) are 5 and 1 parts per million (ppm) respectively, but only when used as 20 percent of a feed ration. Since testing by lateral flow strip takes about 10 minutes per sample, widespread testing at either plants or elevators is logistically challenging. Instances of up to 100 ppm vomitoxin have been found in the eastern Corn Belt, but some level of incidence (about 1 ppm) is present in many areas. Visual screening for both mold damage and the type of mold is reasonably effective at identifying potential problems, but requires training. Preharvest scouting would be a good early warning system when done in an ethanol plant trade area by scouts well trained in the differences among fungi.

Expect to grade incoming corn very professionally and carefully. What was present in the fall is still there; toxins are stable in drying and storage and do not generally increase in storage, although unprecedented extreme spoilage occurred in some temporary storage this year. If load-by-load testing is not feasible, consider making a half-day or full day composite of inbound samples to provide a moving average inventory trend which may be sufficient to avoid problems or alert distillers grains merchandisers. The next step in testing intensity would be compositing by seller/contract, to identify where issues might arise.

Sample test data for two toxins were analyzed to show that ethanol producers would be wise to keep supplies to about one-third the FDA advisory levels in order to accommodate for variability and keep distillers grains below the limits. In the sample case, about half were over the one-third criterion for one or both toxins.

Total damage (visible mold of all strains) will also be an issue. There is field damage as well as considerable damage created by storing too wet or with inadequate aeration. (The U.S. corn market simply did not have enough dryers and good quality storage to accommodate the situation last fall.) As summer approaches, the storage life of 2009 corn will be reached and sudden increases in spoilage from seemingly dry corn are likely by mid- to late summer.

Overall corn quality affects ethanol yield. Total damage generally reduces yield although some fungi create more problems in fermentors than others. Low test weight (TW) has mixed effects. If TW is low because of more starch and less yellow protein, ethanol yields will increase but DDGS yield and protein will fall. Lower protein and lower oil increase yield because of starch substitution. If TW is low because of mold or drought or other disease, then yields may be less. Estimates of ethanol yield can be made to within 0.03 gallons per bushel with accurate measures of protein, oil and specific gravity (seed density, not test weight). These measures can be done in about a minute per test with the near infrared analyzers often found in processing plants.

Charles Hurburgh leads the Iowa Grain Quality Initiative at Iowa State University. Reach him at tatry@iastate.edu or (515) 294-8629.