Michigan producers should carefully monitor corn grain quality in storage

Last season’s cooler than normal temperatures caused lower than normal test weights.

As we begin to ramp up for the 2015 growing season, growers may want to keep one eye on grain quality in on-farm storage this spring. While favorable precipitation levels produced higher than normal corn grain yields across much of Michigan, the cooler than normal temperatures of last season caused much of the crop, especially in Mid to Northern Michigan, to have lower than normal test weights. Extended periods of wet conditions may also have increased the incidence of ear molds, particularly in susceptible hybrids, last season.

Test weight is the measure of pounds per volumetric bushel. In years where the crop struggles to reach black layer, or physiological maturity, test weights often are lower than normal. The low end market standard for test weight for #2 yellow corn is 54 pounds per bushel. However, test weights can vary by as much as 46 - 60 pounds per bushel. Why worry about test weights other than for the potential for being docked at the grain elevator? I asked that question of Klein Ileleji, Purdue University Stored Grain Specialist. He shared that lower test weight is an indication that the corn did not mature fully or that other stresses were incurred by the plant. Additionally, some stresses at growth could make the kernels more susceptible to mycotoxin contamination and breakage during handling.


In regard to storability, Ileleji said that lower test weight kernels don’t store as well as kernels that achieved their full test weight potential. Corn below the 54 pounds per bushel standard can be problematic. Growers should be cautious when considering longer storage of corn harvested at low test weights. Lower test weight corn should also have been dried to below 15 percent moisture for safer storage, and even then should probably not be considered a good candidate for storage into the warmer summer months.

Moisture within grain in bins moves with temperature fronts. In cases with higher moisture corn in storage – and especially in lower test weight corn – grain at the top and in the center of un-cored grain bins is more likely to spoil. In higher moisture situations, corn along the bin walls is also more likely to spoil. Both of these situations can become dangerous when the grain is removed from the bin. Spoilage at the top of grain bins can cause "bridging", a layer of grain that remains intact across the top as grain is removed below the layer of spoilage. This layer may look perfectly normal, but can collapse under the weight of a person walking across the top of the grain mass in the bin, trapping him or her under tons of grain. These situations can also be dangerous at the bottom of bins when growers try to unload corn in storage where columns or caps of spoiled grain are subject to sudden collapse.

What can be done to help protect low test weight corn in storage from unacceptable spoilage? Michigan State University Extension recommends making good management decisions.

Grain condition going into the bin

Evaluate the quality of grain that went into bins last fall, and be prepared to move grain that had low test weights or not adequately dried for longer term storage.

Aeration management

Ileleji advises growers that stored grain should not be warmed in the spring. His suggestion is to leave the grain at the cool temperatures it was aerated to coming out of the cold winter (cool but not frozen). Growers should ensure that the fans are sealed with a cover or plastic to prevent passive (chimney effect) aeration by warm air. If there is a powered vent on the roof, this can be set on a humidistat (set to turn fans on above 60 percent RH) to remove humid air from the headspace at night when condensation occurs. It's important to exchange the headspace air without aerating the whole bulk, which will warm up the grain under warm weather conditions.

 Constant aggressive monitoring

Does corn in your bin pass the smell test? Odors are an indicator of grain quality degradation. Unfortunately, spoilage can happen quickly in bins, so monitoring this way needs to be completed often. Since moisture often migrates to the top of grain bins, monitoring also needs to be done at the top to be effective. A much more comprehensive system of monitoring utilizes temperature sensors that can detect hot spots in the grain mass that can indicate spoilage.

Longer term things to consider

Agronomic - There has been a subtle switch to longer season hybrids and soybean varieties to try to reach higher potential yields across many areas of Michigan. This puts us at increases risk for lower test weights and higher harvest moisture levels in years when we have below normal temperatures for extended periods during the growing season.

Grain Moisture Management - Growers are constantly faced with the challenges of spending more on drying grain or reducing the time that the grain can be safely stored. As grain prices come closer to the cost of production, this decision has become harder to make. The more moisture in the grain, the smaller margin of error there is in stored grain management.

Improved Aeration in the Bins - Increased capacity to move air across the grain in storage can improve your ability to manage grain temperature and moisture, reducing risk of spoilage. Evaluate your bins capacity to deliver cooling and after winter conditioning air efficiently. An often overlooked aspect of aeration is to make sure that there is adequate roof venting to allow the fans to work at optimal efficiency. Again, consider top venting with powered fans to regulate temperature and humidity at the roof headspace. This is often a very cost effective way to improve the aeration capacity and of your on farm storage.

Using Marketing Tools - While on-farm storage can be a cost effective way to stay in the market, it is not the only way to accomplish this task. When grain quality issues are in play, consider carrying your position on paper to reduce risk of storage losses. 


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