Cooler Weather Provides Opportunity To Cool Your Corn

Cooler Weather Provides Opportunity To Cool Your Corn

A lot of corn has been harvested early with high outside temperatures; it requires additional cooling cycles in your bin.

Iowa farmers are now well into harvest, corn before beans in many cases. This is yet another unusual situation. A lot of corn has been harvested early this fall with high outside temperatures, in the over 80 and 90 degree ranges, and it was dried in the same conditions. This means corn is now in bins at much higher temperatures than normal.

COOL IT: Early harvest of corn this fall will require additional cooling cycles to reach desired temperatures in your bin. Weather forecasts predict cooler weather this coming week, providing opportunities to run the fan and cool your corn.

"Early harvested corn will require at least two additional cooling cycles to reach the desired eventual grain temperature of 40F or below," says Charlie Hurburgh, an Iowa State University grain quality expert and professor of ag and biosystems engineering. "The weather forecasts indicate we will have chances to run the fans and cool the corn in the bins next week."

You need to cool down this warmer than normal grain the right way
Follow the proper procedure to cool this warmer-than-normal stored corn down the right way this fall, advises Hurburgh. It starts with making sure you understand what a cooling cycle is and what you need to do. What is a cooling cycle? "A cooling cycle is moving a cooling front completely through a bin of grain and it is done when the average outside temperatures are 10 to 15 degrees F below the grain temperature," he says. How long will that take? It depends on the size of the fan you are using. With 0.1 cubic foot per minute per bushel of aeration, this takes about 150 hours; with 1 cfm/bu, about 15 hours is required.

Safe fall storage means you need to be progressively lowering the grain temperature in cycles, he explains. Because the shelf life of the grain in a bin is temperature dependent, it is important to begin these cycles as soon as a 10 to 15 degree temperature drop can be achieved. With higher initial temperatures, at least two additional (beyond normal) cycles will be needed. If the grain has to wait in the bin for a month to be cooled, the shelf life will be reduced and future spoilage is much more likely to occur.

Update on 2012 grain drying, handling and storage management issues
Quality of grain harvested is going to vary widely this fall, even in the same field. You can expect high and low moisture blends to be going into the combine's grain tank in the same pass through the field, says Hurburgh. Dryers will not equalize variability. Even after cooling and aeration of the dried corn, there can be four percentage points or more in moisture variation among kernels. Moisture variation means shorter shelf life and more storage risk.


Test weight, the best indicator of storability, will also vary. Overall test weights are somewhat below average in the corn that's being harvested in Iowa so far this fall. "It's generally in the 54 to 55 pounds per bushel range, which is what we expected from drought-stressed corn," says Hurburgh. "In severe cases, which can include parts of the same field, 46 to 50 pound per bushel test weights are likely. The combination of generally lower average test weight and highly variable moisture means we should reduce the typical estimates of storage time before loss."

Click on this link--See Crop Quality Issues from the Drought of 2012--for a table listing the typical storage life expectations for corn. Hurburgh says you should reduce the estimated storage times given in the table by at least a third, possibly up to 50%, for corn that's from drought-stressed areas.

Aflatoxin is an issue in some areas, more frequently in Iowa's southern half
Aflatoxin continues to be an issue this fall. In Iowa, scattered incidence is occurring, more frequently south of U.S. Highway 30 and progressively toward the Missouri border. In the northern half of the state, storm damaged, downed corn is the most susceptible. The recent cooler temperatures have been very helpful in controlling increases in aflatoxin.

The ISU Extension ICM Newsletter has had several articles on aspects of the aflatoxin issue published this fall. Go online and read those articles for more information.

"It is very important to contact your crop insurance carrier if you suspect aflatoxin," says Hurburgh, "because there is no coverage once the grain is harvested. Know what your markets are doing to monitor aflatoxin; there are many strategies as we discussed in earlier articles in the ICM newsletter."

If you have an insurance settlement for aflatoxin, it is very important to market the covered grain to a buyer that will assure its use by the correct livestock for the level of aflatoxin the corn contains. Food safety is a growing concern in world markets. You can expect to see more follow up and tracking if there is a recall or health incident related to aflatoxin in corn.

Aflatoxin will not increase in storage if good grain management practices are used
As Hurburgh has described in earlier articles, aflatoxin will not increase in storage if good grain management practices are followed. Cool the grain immediately after harvest (60 degrees F or below) and dry right away if the corn is over 16% moisture. This is not a good year to hold wet grain for later feeding or blending. However, the fungus is not active in cold grain, so normal drying to 15% to 16% and progressive aeration cycles will be sufficient.


There is a problematic drying situation this year, says Hurburgh. Bin dryers, even if stirred, should not be operated at "medium" temperatures (80 to 100 degrees F). These temperatures can create warm corn that could result in an increase in aflatoxin, if the Aspergillus flavus fungus was present in the field, before the grain gets dry. Bin drying at 120 degrees F and up will move the drying more rapidly. In addition, not filling a drying bin to the top at the start of the drying period will also help; less grain will be held at higher moistures.

FDA recently approved a temporary corn blending policy for aflatoxin in Iowa
The federal Food and Drug Administration has recently approved a temporary blending policy for aflatoxin in corn grain in Iowa. This policy was released September 19 by the Iowa Department of Agriculture and Land Stewardship. The key point is that if corn is blended to reduce aflatoxin in the blend to useable levels, the blended corn must be marketed with documentation of aflatoxin levels and the intended use of the corn.

What about soybeans? Any quality issues to watch out for? Soybean harvest is just beginning this week, notes Hurburgh. The warm winds of the past several days should drop the moisture content of soybeans very quickly.

For farm management information and analysis go to ISU's Ag Decision Maker site and Extension farm management specialist Steve Johnson's site

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