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12
Apr
2013
Non-Uniform Corn Emergence and Blackbirds
Author: Jason Kelley, Wheat & Feed Grains Extension Agronomist

How Much will Non-Uniform Corn Emergence Impact Yields?

We continue to see much of our early planted corn struggle to get full stands.   In many instances it appears that we have/or will get a stand after 4 weeks, but plants have emerged over a period of several days instead of the optimal 24-48 hours to emerge that we often talk about for maximum yields.  Below is an example of the uneven emergence that many early planted fields are experiencing (Photo by Kevin Lawson, Corn, and Grain Sorghum Verification Coordinator).

uneven corn emergence

 

 

Is Uneven Emergence Going To Impact Yields?  This seems to be the million dollar question lately and there are lots of opinions out there.  First and foremost when evaluating stands, the most basic question is whether or not you have an adequate plant population.  Stands that are less than 26K plants/acre on irrigated fields are likely going to be replanted, provided replanting can occur within a reasonable time frame.  But lately, the most asked question is whether I should replant even if I have an adequate plant population because the corn came up over a long period of time.  My response is if you have an adequate plant population, you don’t need to replant just because plants did not emerge on the same day.   Although there are going to be exceptions to every rule of course.  In looking for information on this subject, there have been a fair number of trials conducted by Universities over the past several years.  The table below is a summary that was compiled by Iowa State University of several trials from various states and countries evaluating corn yield response to delayed emergence.

 

Estimated Yield  Loss Caused by Late Emerging Plants*
% Late Emerging   Plants

 —————Days Late in emergence —————

6

7

10

12

14

21

 —————Estimated % Yield Loss   —————

17%

-4%

-8%

25%

-6%

-10%

50%

-6%

-6%

-17%

-20%

75%

-6%

-23%

 

*Source:  http://www.agronext.iastate.edu/corn/production/management/early/heights.html

So looking at the above table, if 25% of the plants emerged 6-10 days later than the majority of the corn, it would be estimated that yield loss would only be 4-6%.  Not nearly as great as many of the rumors that are going around.   Of course if plants emerged more uniformly, less or no yield loss would be expected.

As slow as corn has been growing, a 7-10 day difference between emergence between plants would likely only result in a 1 leaf stage difference.  Last year with record warm temperatures in March, plants were only putting on 1 leaf per week during the early stages.

The take home message is that plants may emerge 6-10 days later than the majority of plants and only a 4-6% yield loss would be expected, and replanting should not be needed provided you had adequate plants/acre.

Blackbird Problems

Many producers are having troubles with blackbirds this year.  We typically see more problems with blackbirds in March than in April.  However due the wet and cool prolonged spring, the birds seem to be sticking around longer and are targeting newly emerging corn.  I’ve had a couple producers say they had fields that survived the cold and wet weather only to be lost from blackbird feeding.  After the fact there is not a lot that can be done besides chasing the birds away from the field, which is probably a futile attempt because they will usually just fly a little ways down the field.  Producers who replant corn in these fields with bird problems should consider the bird repellent Avipel®, which has a 24c label for use in Arkansas corn.

 

Blackbird Feeding on Corn

 

 

 

 

 

 

 

 

 

Contact Information: 

Please contact your local county extension agent in Arkansas or the author by email at jkelley@uaex.edu, or by phone at 501-749-6207 if you have questions or comments regarding this newsletter.

 

 

 

 


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