Wet Weather Creates Challenges For Harvest

• Fungus development. Continued wet weather and warm humid conditions are retarding drydown and are encouraging fungus development on ears (see Figures 1 and 2 below). Some fungi produce mycotoxins harmful to animal and human health. The wide range of fungi on samples this year creates the unusual potential for several mycotoxins. Some fungi, such as diplodia ear rot, do not produce mycotoxins while others such as fusarium or aspergillus can be toxigenic. Expect feed mills and ethanol plants to screen early harvest samples for toxins. Field scouting can help identify problems before harvest.

• Moldy grain. Moldy grain will have shorter storage life than 'clean' grain held at the same moisture and temperature. The data in Table 1 represents the long term averages. For grain carrying field mold, expect perhaps 60% to 70% of normal shelf life. 

• Storage life. The storage life of grain starts immediately after harvest and is shortened significantly when stored at warm temperatures. One day of holding warm, wet corn before drying can use as much as 50% of the storage life, therefore increasing the likelihood of storage problems next spring and summer. Holding wet corn can also result in blue eye mold development, which lowers the Grade but does not produce mycotoxins. Soybeans are sometimes overlooked in the need to cool grain immediately; yet soybeans are more often harvested in warm weather compared to corn.

• Harvest early. Harvest early and expect to dry the corn. Avoid holding wet grain before drying. Dry rapidly.

• Watch dewpoint temperatures. Cooling the corn out of the field and after drying will be a challenge; watch the dewpoint temperatures. You will never cool the grain below the dewpoint. Ongoing temperature monitoring is key to successful storage. Recent developments in carbon dioxide monitoring have created another way to monitor spoilage; deteriorating organic matter always produces CO2 emissions.

• Drying methods. Slower drying methods will require careful monitoring. There will be potential for additional spoilage before the grain dries. This would apply to both natural air and low temperature systems. You can increase drying speed in these systems by reducing the depth, but the tradeoff is having less grain in the dryer. 

• Bin dryer temperatures. Operate gas-fired bin dryers at temperatures above 120 F, but not over 160 F.

• Management of pile grain. Temporary piles should be at commercial facilities, not on farms. Small piles spoil more rapidly than large ones. Management of pile grain is labor intensive, and often requires very short notice decisions about moving the grain. Larger piles are also easier to aerate.

• Do not mix old and new crop grain in the same bin. The old crop has used much of its storage time and the new crop is still equilibrating moisture. Rotate stocks if you can. Be sure to separate the crop years and draw the center cores out of all bins, corn and soybeans alike.

• Testing for toxins. Commercial grain handlers and processors should expect to receive grain with higher levels of damage and foreign material. We do not know yet if this will create mycotoxin issues. One way to track the situation in a given area is to collect a 10-lb daily composite (some grain from each of the deliveries in a day) for toxin testing. The USDA-GIPSA grain inspection agencies have the capability to test for the mycotoxins of most concern - aflatoxin, vomitoxin, zearalenone, and fumonisin. Toxin test kits are now simplified to the point where elevators and processors can do their own, but the USDA results provide a good benchmark. Results after 7-10 days should indicate whether there is a problem in an area. The composites also provide an opportunity to check the accuracy and completeness of on-site grading.

• Grain handling safety. High volumes and wet corn, are the common ingredients for grain handling accidents, both entanglements and engulfments. Nothing is worth taking shortcuts on safety.  

Conclusion

In summary, given expected weather patterns, there will be large volumes of wetter and potentially moldy corn this year. Use test weight and visual mold presence as a measures of future storability. Identify in advance bins that will be kept for the long term, including possibly retained 2015 corn. Separate crop years in storage, and scout fields for grain molds before harvesting. Low test weight and moldy corn are likely to go together. Dry quickly with as little wet corn holding time as possible. Once in storage, keep track of temperatures regularly and consider adding CO2 monitoring to your stored grain control process.