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Calculator to estimate how long it may take for in-field corn drying

Date of earliest, latest and average first 28 degree frost. 

The corn cropping year can end due to physiological maturity or a 28 degree killing frost.  When looking at air temperature data from 1981 through 2010 for five different northwest Minnesota locations, the date of the earliest 28 degree frost ranged from September 13 to 20, the date of the latest frost ranged from October 25 to November 3 and the average frost date ranged between October 2 and 9 (Table 1).  
Table 3. Date of earliest, latest and average first 28 degree fall freeze for locations in northwest Minnesota (source: U2U GDD calculator)
Fall 28 degree freeze
Thief River Falls
Sep 20
Sep 20
Sep 15
Sep 15
Sep 13
Nov 3
Oct 29
Oct 25
Oct 25
Oct 25
Oct 9
Oct 6
Oct 5
Oct 4
Oct 2

Ideally, to allow some complimentary in-field drying to take place, physiological maturity would occur before temperatures drop in fall.  As cooler air temperatures tend to hold less moisture, the later into the fall that it takes to reach black layer the less efficient in-field drying will be.

Corn dry down calculator.  

Researchers at Iowa State University recently released an online tool to help people to estimate how quickly corn may dry in the field.  While developed in Iowa, the team successfully tested the tool using real-world data as far north as North Dakota and Minnesota.  

As few corn crops (if any) in the region have yet to reach physiological maturity, this tool can be used now to run through various scenarios given a crop’s geographic location and projected date of and kernel moisture at physiological maturity.  To read more about this calculator from the perspective of the developers visit this article on the ISU Extension Integrated Crop Management Blog.  The corn drydown calculator can be found here.


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