The vast majority of corn in Manitoba is in the bin, but what about those few fields that may not be harvested yet? In some cases weather conditions may have made it difficult for farmers to harvest corn in the fall, but some farmers may decide that the corn moisture level and costs associated with drying mean that it is more economical to leave corn in the field to let it dry down naturally over winter.
Just how much dry down can be expected over winter? The amount of drying that occurs in the field depends on the corn maturity, variety, and moisture content, as well as environmental factors such as temperature, humidity, solar radiation, and wind speed. Field drying is extremely slow in the winter, and corn will only dry to about 20 to 21% moisture content. In a typical year, it is expected that corn will dry approximately 11-12% in October, 4-5% in November, and just 2% per month in December and January (Table 1).
Table 1. Estimated corn field drying
|EMC (%)*||GDD||PET (in.)||Estimated Drying (% pt.)|
*EMC – equilibrium moisture content, GDD – growing degree days, PET – potential evapotranspiration 1EMC is the moisture content to which corn will dry and is based on air temperature and relative humidity
Source: Ken Hellevang, 2009. 2009 Post-harvest tips for later maturing corn. NDSU Extension Service.
Risks of overwintering corn Heavy snowfall during the winter can cause significant amounts of lodging resulting in yield losses. Root and stalk strength should be taken into consideration when deciding if a field should be overwintered. Research conducted at the University of Wisconsin examined corn yield loss during the winter (Table 2).
This researched showed that in 2000, a year with heavy snow cover, yield loss was much greater than in 2001, a year with very little snow cover. Standing corn may result in more snow catch and slow soil drying in the spring, which could delay planting.
Table 2. Percent yield loss of corn left standing in the field through winter at Arlington, Wisconsin.
Source: Schneider and Lauer, 2009. Weight risk of leaving corn stand through winter. UW Extension -Team Grains. http://corn.agronomy.wisc.edu/Teams/TG001.pdf
Corn can be harvested throughout the winter if conditions are cool and there isn’t much snow. If stalks stay standing throughout the winter, and ear drop and wildlife damage are limited, corn can get through the winter without much yield loss. Yield loss throughout the winter will vary by hybrid and environmental conditions.
If you are planning to over winter corn please contact your local MASC agent.
Submitted by Anne Kirk, Cereals Specialist, Manitoba Agriculture