ND Corn Still Behind

Season's growing degree days are about same, but much of crop was planted later than usual.

Published on: Sep 2, 2011

Joel Ransom, NDSU Extension agronomist, thinks North Dakota's corn crop may not mature and dry down adequately before the season's first killing frost.

"As far as temperature is concerned, the 2011 growing season is shaping up to be similar to the long term average, at least for the eastern third of the state," he says. "In fact, growing degree day accumulations for this region of the state are within 30 GDDs of the long term average. GDDs for the western two-thirds of the state, however, are running 100 to 200 GDDs behind the long term average."

But more than half of all the corn was planted after May 24, which means that much of the corn in the state is lagging significantly behind where it should be.

"At Wyndmere, delaying the planting of corn until May 24 "cost" the crop 184 GDDs," Ransom says. "Delaying the planting until June 1st "cost" the crop 317 GDDs."

The following are a things that Ransom says to consider when planning how to managing a late-maturing corn crop:

Corn that reaches physiological maturity (PM) has a moisture content of 30-32%.  Moisture content prior to PM declines as additional starch is deposited in the developing kernel. Moisture loss after PM is by evaporation. Grain from plants that are killed prior to PM will be shriveled and have low test weight because they lack sufficient starch to fill out the kernel.

The rate of moisture loss after the death of the plant via evaporation, whether the kernel has reached PM or not, will largely depend on air temperature. Relative humidity can play and important role in evaporation, but air temperature is the most dominant factor in North Dakota. Warm air has the ability to hold more water vapor than cold air, so warmer air temperatures are able to draw more air out of the drying kernel than cooler temperatures. A good rule of thumb is that most field-drying that is going to occur in the fall will occur prior to Nov 1. Research shows average moisture losses of between 0.25% to 0.33% per day during late September and October. Moisture loss after Nov. 1 was much less. However, if November is warm drying will continue.

Leaving the corn crop over the winter has been profitable when corn is excessively wet and difficult to harvest in the fall.  Because of the limited water holding capacity of air in the winter, the rate of corn drying during the winter is very slow. In 2009/2010, the average moisture loss was about 0.1% per day from Dec. 1 to Feb. 21. Grain that had 32% moisture in early December reached 24% moisture on Feb. 21. In another study starting with relatively dry corn (18%) in 2008/2009, researchers observed minimal decline in grain moisture until the beginning of March, at which point the rate of decline accelerated until the corn was harvested in early May.

The test weight of wet corn increases with drying, except for corn with more than 42% moisture where the opposite is true. Field drying during the winter may improve the test weight of corn that is excessively wet better high temperature drying, but don't expect more than a couple of pounds difference.

Yield losses can be substantial during the winter due to snow, winds and wild animals. Most yield loss is associated with ear drop and lodging. If the crop goes into the winter with good stalk strength, it is more likely that yield losses will be less than if the crop has poor stalk quality.

Source: NDSU Crop and Pest Report