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Don’t manage against the grain

By Staff | Dec 18, 2009

Poor quality corn has been a common lament across most of Iowa this season as grain struggled against a plethora of unhelpful growing conditions.

Iowa State Extension ag engineering specialist Greg Brenneman, speaking to corn and soybean producers in meetings last Friday in Worth and Cerro Gordo counties, gave advice on storing this year’s crop.

Brenneman said that a late harvest, plus low-quality grain, has created a different kind of situation for farmers drying and storing the 2009 harvest.

He noted that successful grain storage requires clean grain dried to the recommended moisture followed by aeration to a cool uniform temperature. Stored grain will need to be checked frequently and any problems that arise will need to be handled quickly.

A bin of corn is 40 percent air and 60 percent corn. A bin of soybeans is 35 percent air and 65 percent soybeans at filling time.

Corn stored in a bin at a grain temperature of 50 degrees and a relative humidity of 60 percent will achieve an equilibrium moisture of 13.8 percent in the bin. Lower humidity and higher temperatures will reduce the equilibrium moisture in the bin. Soybeans will reach 11.2 percent under those same conditions.

Poor quality corn has been a common lament across central Iowa this season. Above is an ear of freshly harvested, immature corn, with mold. Three weeks of cold, wet weather ended the drying down season early.

Brenneman’s data showed grain stored at a temperature of 40 degrees at 15 percent moisture has a maximum storage life of 29 months. Raising the moisture one percentage point reduces the maximum stored time to 15 months.

Grain temperatures can vary within the bin, Brenneman said, and moisture migration from interior air convection currents is responsible for the problems of crusting at the top of the stored grain. This is why proper cooling is necessary.

Grain must cooled to between 28 to 35 degrees by December, Brenneman said, and maintained at that temperature during the winter by intermittent aeration. When spring arrives, keep the grain cool by sealing the fans and intermittently ventilating the headspace in the bin.

The University of Minnesota Extension has a fans program that uses a spreadsheet to calculate cooling requirements based on the crop, bin floor type, grain depth, airflow, number of fans and arrangement.

Brenneman showed that moisture is removed from corn 5 to 9 bushel points/hour using natural air. Air temperatures of 120 degrees increases the removal rate to 50 points and at 160 degrees, 80 bushel points/hour.

Brenneman advised to not dry at temperatures between 80 and 110 degrees because 0corn can spoil faster than it dries.

When checking stored grain, Brenneman said to run the fan and check the temperature and the smell of the stagnant air in the bin. An aeration fan rated at .1 cubic feet per minute/bushel will have a complete air exchange in five minutes.

A moldy or musty odor or a temperature rise of 3 to 4 degrees indicates a developing problem. A sour or fermenting odor means there is a big problem.

Stored grain needs to be checked every other week through the winter and every week the rest of the year. Brenneman said to climb in the bin looking for crusty, moist, sticky, or warm grain. Probe the grain with a thermometer looking for warm spots.

If a problem is detected, turn on the fan and run it until the grain is cool. Larger problems may require the use of a screw-in aerator, removing the troubled area, or unloading the entire bin.

Greg Brenneman said more information on grain storage could be found at iowagrain.org.

Contact Clayton Rye by e-mail at “mailto:crye@wctatel.net”>crye@wctatel.net.

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