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Extension > Minnesota Crop News > Corn grain drying rates

Wednesday, August 24, 2005

Corn grain drying rates

Dale R. Hicks, Agronomy and Plant Genetics

Drying costs will be higher this fall because LPGas prices have and are rising quickly during the past few weeks. Corn growers may want to delay harvest to allow for more field drying which could reduce drying costs. How much field drying can be expected?

Field drying is an evaporative process of moisture moving out of kernels through the husks. High temperature and low humidity are the primary factors, which drive the rate of field drying. Husk looseness is an important plant characteristic that helps to speed kernel moisture loss. Other factors are wind speed and sunshine hours that contribute to field drying.

On average for the state, corn is physiologically mature September 19 when grain is about 32 percent moisture. During the last half of September, grain can lose 3/4 to 1- percent moisture per day, depending upon the conditions, primarily air temperature. Using 3/4% per day for the last 10 days of September, grain should drop about 7.5 points or dry to 24.5% moisture by the end of September.

During the first half of October, grain usually loses 1/2 to 3/4% per day. Using 1/2% per day, grain should drop another 7.5 points during the first half of October, getting the moisture content down to about 17%.

During the last half of October, the moisture loss can be 1/4 to 1/2% per day. Kernel moisture content rarely drops during November because air temperatures are so low.

For corn that reaches maturity before September 19, there will be more days with the higher rate of kernel moisture loss and more time for field drying. For corn that matures later, there is less opportunity for field drying because drying rates are lower and there are fewer calendar days for drying and harvesting.

The tradeoff of delaying harvest to allow for more field drying could be 1) increased preharvest losses due to dropped ears (corn borer tunneling in the shank), 2) the weather risk due to less calendar time to harvest, and 3) less time after harvest for other field operations such as fertilizer application.

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