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Fall versus spring corn harvest

Angie Peltier, UMN Extension and Joel Ransom, NDSU Extension

Recent wet weather.  The winter storm that brought with it rain and then snow to northwest Minnesota dropped between 0.5 and 4 inches of rain (Figure 1).  This topped off an already wet month, with total rainfall ranging between 5 and 15 inches (Figure 2). 

Figure 1. Between October 5 through 12, the region as received widespread precipitation amounts between 1 to three inches. Source: National Weather Service.

Figure 2. Over the past month, locations have received anywhere from 5 to 15 inches of precipitation! Source: National Weather Service.
From September 11 through October 10 between 4 and 8 inches of rain has fallen, 0 to 6 inches more than normal throughout the region.  The National Weather Service’s Climate Prediction Center predicts above normal precipitation for October (Figure 3) and near normal precipitation through December (Figure 4).  
Figure 3. US One month (Oct 2019) precipitation outlook. Areas shaded in green and brown have an elevated chance of above and below normal precipitation, respectively (Source: NWS-CPC).

Figure 4. US three month (Oct-Dec 2019) precipitation outlook. Areas shaded in green and brown have an elevated chance of above and below normal precipitation, respectively (Source: NWS-CPC).

Corn maturity and kernel moisture.  

In my travels throughout northwest Minnesota over the last couple of weeks the only corn coming out of fields was being chopped for silage.  In corn that has reached physiological maturity (ie. R6, black layer) kernel moisture can be as high as 35%.  Corn that has not yet reached maturity will likely be killed by the upcoming frost and have average kernel moisture higher than 35% (Figure 5). 

Figure 5. The relationship between percent of maximum yield, corn growth stage milestones and kernel moisture content (Adapted from Ransom, 2013).

Managing risk. 

Corn producers strive to strike a balance between allowing time for in-field grain drying to both reduce drying costs and the chance of harvest-related kernel injury and risking weather that delays harvest, causes stalk breakage or encourages animal feeding.  In-season stresses can result in poor stalk strength and pathogens and insects can degrade ear health and shank integrity.  A good understanding of the health of the crop before the snow flies can help farmers to best manage risk.  Even after snow has fallen it is likely worthwhile to go out and push-test stalks and check on the health of ears.  Good stalk strength is a must for any crop left in the field for drying for any prolonged period this fall/winter.  Fields with lodging or any amount of ear drop should be harvested earlier than those that exhibit good stalk strength.

Moisture and yield loss in corn left standing over winter.  

Generally, by the first of November because of cold temperatures, conditions are not favorable for field drying of corn in the northern Plains.   However, this does not mean that corn will not dry down over the winter months.  Dr. Joel Ransom, Extension cereal crops agronomist in the NDSU Dept. of Plant Sciences, followed moisture loss during the 2009 winter in North Dakota’s Cass County and found kernels that had started out above 18 percent moisture in mid-December dropped to less than 14 percent moisture by April.  Dr. Joe Lauer, corn agronomist at the University of Wisconsin, studied moisture loss over five Wisconsin winters and found that grain moisture stayed above 20 percent during December and January but fell to 10 percent by April (Schneider and Lauer, 2009).

After seeing visible ribs on foraging white tail deer during the spring months of 2019 a meal of corn would likely be a welcome site to deer over the 2019-2020 winter.  The Lauer team in Wisconsin followed yield lost from corn left standing over winter in 2000 and 2001 (Schneider and Lauer, 2009).  In a year with little snow (2001) yield losses ranged between five and eighteen percent depending on when the crop was harvested while in a year with a lot of snow cover (2000) yield losses ranged between 38 and 65 percent.  Many farmers in the region have successfully harvested corn after leaving it in the field for most or all of the winter.  There are obviously risks. Unfortunately, it is very difficult to predict the type of winter we may have and the level of animal depredation that may occur in a given location.  When deciding on keeping corn over the winter, remember that dealing with corn residues after a spring harvest will likely delay any spring land preparation and planting, that could put your 2020 at a disadvantage. 

Per bushel drying costs at local elevators can range between 3 and 5 cents per percentage point above 14.5% moisture.  With current corn at $3.25 per bushel one could lose up to 20 percent of the crop by leaving it in the field or pay up to 65 cents in drying costs and still end up in the same place financially (Table 1). 

Table 1. Break-even point between total drying cost versus field loss during winter field drying (source: Schneider and Lauer, 2009)

Percent yield loss through winter
Corn price

Break-even drying cost ($/bu)

Crop insurance.   

According to the USDA’s Risk Management Agency that administers crop insurance, crop insurance coverage begins either on the date that RMA accepts an application or when the crop is planted (whichever is later; RMA, 2019).  But there are more ways that the coverage of a corn crop can end, including: total destruction of the crop, harvest, final loss adjustment, crop abandonment, September 30 for silage corn or December 10 for corn grown for grain (whichever occurs earliest).   Please keep in touch with your crop insurance agent should either you suspect an insured loss or the December 10 deadline approaches.

Literature cited.

Lauer, J. 2004. Some pros and cons of letting corn stand in the field through winter. Wisconsin Crop Manager. Online. Verified October 10, 2019. 

Schneider, N. and Lauer, J. 2009. Weigh risk of leaving corn stand through winter. UW Extension publication. Online. Verified October 10, 2019.


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