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While in-field drying still normally occurs in October, the best drying conditions are usually in late September. ÊWith a record cool first half of October, field dry down has been slow.
In 2009, it is anticipated that much of Iowa's corn crop will be harvested in the low to mid 20% moisture range as opposed to the mid to upper teens of a couple of years ago. Ê
A good look at expected field dry down is covered in a Minnesota website at: http://www.extension.umn.edu/cropenews/2008/08MNCN26.html
It takes 15-20 Growing Degree Days (GGD) to drop corn about one percentage point of moisture. ÊWith normal weather conditions, we can expect early October corn dry down of 0.5 to 0.75% per day and decreasing to less than 0.33% per day by late October. ÊBy November, little additional in-field drying can be expected. Ê
Based on these drying rates, corn maturing to black layer on October 1 can still be expected to be in the low 20 percent moisture range by late October. Ê
One way to cut drying costs and increase the capacity of a high temperature dryer is to cool the corn after taking it out of the dryer. Cooling the corn after the dryer can remove an additional 1-2 percentage points of moisture. ÊYou can take this a step further with dryeration. ÊCorn is unloaded hot from the dryer and held hot or "tempered" for 4 to 12 hours without aeration in a holding bin. ÊIt is then cooled and moved to storage. Ê
About 2 to 3 points of moisture will be removed during the delayed cooling. Ê
Dryeration boosts dryer capacity, improves corn quality, and reduces energy use. ÊIt is important to move the corn to another bin after cooling with dryeration because of condensation that will occur in the cooling bin.
With the rapidly fluctuating propane prices over the last several years, natural air drying has become more cost competitive. ÊUnder average weather and drying conditions, electricity costing $0.10 per kWhr for using only fans for drying compares to about $1.75 per gallon LP prices with average high temperature dryers. Ê
To make natural air drying work, adequate fan sizes are needed and corn should be 22 percent or less in moisture content. ÊFan capacity should be greater than 1 cfm/bushel which roughly equates to about 1 horsepower per 1000 bushels. Ê
Drying depths should be limited to about 16 ft. Ê
Another way to greatly increase the capacity of high temperature dryer and save on drying costs is to use combination drying. Ê
This is using the high temp dryer to dry corn to under 20 percent moisture and then finish drying in a natural air bin. ÊThis combination drying can more than double the capacity of the high temperature dryer and save 10 to 20% on drying costs based on current LP and electricity prices.
Producers are encouraged to seek ways to reduce corn drying costs, but they should avoid the temptation to under-dry corn. ÊCorn that is too wet will spoil when warm weather arrives in spring. ÊAlso, do not cut corners when operating aeration systems. Ê
Even if corn is adequately dried, it can spoil in storage if the grain is not adequately cooled. Corn should be aerated to cool it below 40F for winter storage. Ê
You can get more information about grain drying, handling, aeration and storage from several publications available through your County Extension Office or MidWest Plan Service at http://www.mwps.org/ or by calling 800-562-3618. They are:
Dry Grain Aeration Systems Design Handbook, MWPS 29
Grain Drying, Handling and Storage Handbook, MWPS-13.
Low Temperature and Solar Grain Drying Handbook, MWPS-22
Managing Dry Grain in Storage - 2nd Ed, ÊAED-20
