Harvest: better late than never

We use sayings like “better late than never” to express the thought that it is better to do something late than to never do it at all. Likewise, when it comes to corn, not harvesting is not an acceptable option in most situations. As I write this column in mid-December, 4% of Iowa’s corn remains unharvested; that’s more than 500,000 acres — half a million! Iowa has experienced one of the slowest harvest rates in history.

All of this follows on the heels of estimates for the highest corn yields in Iowa history. According to November estimates by the USDA National Agricultural Statistics Service, the state may average 183 bushels per acre. That’s 2 bushels higher than the previous record of 181 bushels per acre set in 2004!

The cool-growing season of 2009 undoubtedly in part set up this high yield potential. On the other hand, it also undoubtedly slowed crop development and maturity. This coupled with a wet fall slowed harvest.

In addition, Iowa experienced one of the worst blizzards in the state’s history on Dec. 8-9 with more than a 14-inch blanket of snow accumulating in some areas. Wind gusted to more than 45 miles per hour. Drifts up to 5 feet invaded end rows of unharvested corn. Most farmers with corn still in the field then will not likely have the opportunity to complete harvest for some time. What happens to corn as it overwinters in the field?

If little snow occurs and wildlife damage is minimal, stalks may remain upright, shanks retain ears and yields will be little affected by waiting until spring to harvest.

As the winter wears on, stalk quality and ear retention remain top on our list of concerns, especially considering the intense way the winter started this year. Both of these traits vary with hybrids and growing environments. Ears with less grain will likely remain attached to the stalk more than heavier ears -— an interesting advantage for low yields!

Field losses over winter

Joe Lauer, University of Wisconsin Extension corn agronomist, researched overwinter field losses in a two-year study. In a year with little snow, maximum yield loss of 18% occurred when harvested the following spring. In a year with heavy snow, spring yield reductions of up to 65% occurred.

While working at the University of Nebraska a few years ago, Fred Roeth, retired Extension weed specialist, and I conducted a study that required multiple harvests after black layer, physiological maturity. A late-October blizzard in one of the years dropped 23 inches of snow on the study. Ear drop and stalk breakage added up to a total of 32 bushel-per-acre harvest losses, or 19% of the total.

With corn overwintering, two additional concerns arise:

• Expect an invasion of volunteer corn in 2010 if you experience large harvest losses associated with late harvest. A study by Bob Hartzler, Iowa State University Extension weed specialist, found that a single volunteer corn plant per 10 feet of row can reduce yield by up to 1.3% in corn and even more in soybeans.

Considering that it takes two kernels per square foot to add up to 1 bushel-per-acre harvest loss, even a small harvest loss could create a much larger problem of yield-robbing volunteer corn. Adjust crop rotations or herbicides to address this potential problem if stock cows as gleaners aren’t an option.

• Do not expect grain molds that concerned us this past fall to go away. Alison Robertson, ISU Extension plant pathologist, explains that although mold growth on ears will slow during winter months, it will not be killed. Expect mold growth to resurge in the spring with wetter grain prone to mold development.

Corn breeders do not select for hybrids to withstand the intense rigors of winter weather, and corn growers don’t plant corn intending it for harvest nearly a year later. Nevertheless, it does happen. Harvest when possible; as the saying goes … “better late than never.”

Elmore is Iowa State University Extension corn agronomist.

For more information, visit www.agronext.iastate.edu/corn.

This article published in the January, 2010 edition of WALLACES FARMER.

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