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How Fast Will Corn Dry Down in the Field?
Many factors can contribute to dry down. Plant characteristics can influence in-field dry down, but weather conditions strongly influence dry down.
Since weather is such a large factor, kernel moisture loss for any particular day could be very high or low depending on temperature, humidity, sunshine, or rain for each day. When it is warm, sunny and windy corn could lose a point a day, but on cool, cloudy or rainy days it may be zero.
Why is this? Kernel drying following black layer is entirely due to evaporative moisture loss. So, with no sunshine, there will be very little drying. Under favorable weather conditions, here is an example of average moisture loss:
|Harvest Season Stage||Points of Moisture per Day|
|Sept. 15 to 25||3/4 to 1|
|Sept. 26 to Oct. 5||1/2 to 3/4|
|Oct. 6 to Oct. 15||1/4 to 1/2|
|Oct. 16 to Oct. 31||0 to 1/3|
|Nov. 1 and later||0|
Source: D.R. Hicks
Corn dry down rates are also directly affected by growing degree unit accumulation (GDD) and the cool summer has put us behind on GDD’s further slowing the dry down of corn.
When weather conditions are not helping in-field drydown, hybrid characteristics that influence drydown will become more important.
Hybrid characteristics that affect dry down:
- Kernel Pericarp Characteristics: The pericarp is the outermost layer of a corn kernel (botanically; the ovary wall). Thinner or simply more permeable pericarp layers have been associated with faster drying rates in the field.
- Husk Leaf Number: The fewer the number of husk leaves, the more rapid the grain moisture loss. In fact, modern hybrids have fewer husk leaves than those commonly grown years ago.
- Husk Leaf Thickness: The thinner the husk leaves, the more rapid the grain moisture loss.
- Husk Leaf Senescence: The sooner the husk leaves senesce (die), the more rapid the grain moisture loss.
- Husk Coverage of the Ear: The less the husk covers the tip of the ear, the more rapid the grain moisture loss.
- Husk Tightness: The looser the husk covers the ear, the more rapid the grain moisture loss.
- Ear Declination: The sooner the ears drop from an upright position after grain maturation to a downward position, the more rapid the grain moisture loss. In particular, husks of upright ears can "capture" rainfall.
Two hybrids that differ by day of relative maturity will usually differ by ½ point of moisture if planted on the same day. Remember though that relative hybrid maturity ratings are most consistent within a brand of seed, not necessary between seed companies. This can help explain why a 109 day corn from one company could be wetter at harvest than a 110 from another company.
Reference: Purdue University, R.L. Nielsen URL: http://www.kingcorn.org/news/timeless/GrainDrying.html