Extension News

Grain Quality Problems Appearing in Parts of Northern Iowa

9/27/2007

AMES, Iowa -- “Iowa crop producers in north central and northwest Iowa need to isolate grain quality problems now,” said Charles R. Hurburgh Jr. He is the Professor in Charge, Iowa Grain Quality Initiative, which is a part of Iowa State University (ISU) Extension. Here is his analysis of the reported problems with this year’s crop.

Isolate Grain Quality Problems

By Charles Hurburgh
Professor, Agricultural and Biosystems Engineering
Professor in Charge, Iowa Grain Quality Initiative

Reports of grain quality problems in northwest Iowa have been received. These problems are attributable to the erratic weather patterns experienced in that region this season -- little rainfall in June and July, extreme rainfall and wind in early August, followed by frost in mid-September. Corn and soybeans that were already stressed from the lack of moisture, then sat in wet soil or standing water in August.

Stressed grain is more susceptible to mold and other deterioration. Plants flattened or standing in water are a ready target for a much wider range of molds than would normally be expected, especially the potential mycotoxin-producers Aspergillus, Fusarium and Gibberella. Elevator operators report cases of mold damage levels 5 percent and higher in the current corn and soybean crops. Odor problems have accompanied the mold in a few instances.

In normal years, overall mold damage levels are generally less than 2 percent in freshly harvested corn. High damage levels in harvested grain create challenges for grain grading, particularly in the harvest rush. Damaged corn sharply reduces the future storage life of the grain. The early frost in soybeans added some green soybean damage to the weather damage caused by heavy rain and wind. (See ISU Extension publication  Frost Damage to Corn and Soybeans, PM 1635, for more on handling frost damaged grain.) Corn that had black layered, even if high moisture, was past experiencing economic injury from frost. However, corn that was green likely will have lower test weights, which is another source of shorter storage life. So far, the reports have not been widespread.

Storage and harvest management will be particularly important. Field damaged grain, regardless of reason, should not be mixed with good grain. Producers should harvest around water holes, downed grain and frost damaged areas. Do not mix damaged grain with good grain in storage either. The damaged or low test weight grain must be aerated immediately to reduce temperature and equalize moisture. Odor and mold color intensity may be abated as well by aeration, although strong “barnyard” type odors likely will not go away.  

Field damaged grain will not store beyond the winter months. Maintain 1 to 2 percentage points lower moisture than normal grain (for example: 13 percent corn instead of more typical 15 percent). Check with crop insurance providers to see if adjustments may be needed, and how to represent the areas to be adjusted. 

Accurate grading of field-damaged grain is always difficult in the rush of harvest. Particularly expect end users, such as ethanol plants and soybean processors, to increase their level of grading because mold and weather damage reduce processing yields/byproduct quality. An Official USDA grade is the standard against which buyer analysis should be compared. It is important that company graders be trained to match USDA graders. Alternatively, samples can be submitted directly to USDA grading agencies but this process is slower and more costly. In the event of a dispute, use an Official grader.  The variety of damage types will be very challenging to evaluate. See http://www.gipsa.usda.gov/GIPSA/webapp?area=home&subject=fc&topic=fsp to locate the official agency in your area.

If you are planning to feed corn from flooded fields, it would be wise to get a mycotoxin analysis before harvest. The wide variety of molds on these samples may mean a range of mycotoxin possibilities –- aflatoxin, vomitoxin, fumonisin primarily. Veterinarians can submit samples to the Iowa State Veterinary Diagnostic Lab. Alternatively, official USDA grading agencies can do quick tests for these toxins. Toxins concentrate in the distillers grains at three to four times the levels in the corn. Expect ethanol plants to do quick screening tests on some inbound grain, especially on low test weight corn ( less than 50 lb/bu).  Please see ISU Extension publication, Aflatoxins in Corn (PM 1800), for guidelines on sampling and sample handling related to mycotoxins. The sampling procedures apply equally well to the other mycotoxins.

The extreme weather variations have caused a variety of quality problems. It will be important to isolate problem grain from good grain.  Mixtures will take on the storage, odor and handling properties of the poorest fraction, creating loss and utilization issues for the entire batch. While identification of inappropriate mixtures is sometimes difficult at market points, it is the responsibility of every market participant to offer safe and merchantable products. Careful harvest and storage management will be needed to minimize the impact of these weather conditions.

Frost Damage to Corn and Soybeans (PM 1635) and Aflatoxins in Corn (PM 1800) can be ordered through any ISU Extension county office, online at https://www.extension.iastate.edu/store/ or by calling the ISU Extension Distribution Center at (515) 294-5247.

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Contacts :

Charles Hurburgh, Ag & Biosystems Engineering, (515) 294-8629, tatry@iastate.edu

Jean McGuire, Extension Communications and Marketing, (515) 294-7033, jmcguire@iastate.edu