Warm temperatures and low humidity field dries corn

Corn harvest has started but not in full swing. Corn grain moisture is high and growers are hoping that warm windy weather will reduce grain moisture. During this past week, corn grain moisture moving downward but the forecast for rain this week has the possibility of slowing the field drying of corn.

Corn moisture at physiological maturity is around 30%. Mature kernels will have what is called a black layer formed at the kernel tip which indicates that the kernel is now separate from the cob and the kernel will not be taking in more dry matter. Once the corn kernels are physiologically mature, the kernel moisture continues to decrease due to water evaporating from the kernel.

Field drying of corn is influenced primarily by weather, that is, temperature and humidity. Warm temperatures and lower humidity speeds field drying of corn grain.

Typically, dry-down rates vary from 0.4% to 0.8% moisture per day. In early fall, when we have warm, lower humidity days, dry down rates will be high. Whereas, cool wet days will slow moisture loss to even as much as zero. To put this in perspective, if we have corn grain at 30% moisture, it may be a range from two to four weeks for the grain moisture to move to 15%.

Since some area corn fields were late planted, late planted corn will be slower to lose moisture as the plants mature later and then as we move to late September, cooler temperatures set in. Typically, moisture loss will be greatest in first part of September and slow as we move into October. If one has wet corn in November, it should be harvested and one should use heated air to dry corn so it can be safely binned.

Field drying saves drying costs but only to a certain extent. If you decide to wait to harvest, watch for stalk rot and realize that you have an opportunity to lose some yield if we have high winds. Field losses of corn typically average 1% per week in October then moves up 3% in November per week.

Local dealers report that stalk rot is showing in area fields. Be sure to pinch the base of the stalk to see if the rind is soft and if so, you will want to harvest those fields which are of a high risk of lodging to prevent field losses.

For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.