A number of people have had concerns about their corn crop after cool, wet conditions this spring in North Carolina. It is important to make the right decisions when considering replanting to avoid unnecessary costs and yield losses later in the season.
Here are some guidelines for determining if you should replant corn from Ron Heiniger, North Carolina State University cropping specialist, and Wes Everman, NC State weed specialist:
Should I replant?
The first thing to do when evaluating your corn stand is to critically examine your population and not make quick decisions. Determine what your stand currently is, the current date, and if it will economically be viable to replant. Mark off a section of row representing 1/1000th of an acre.
Within this section, remove the dead plants count those that remain including viable seedlings that have yet to emerge. Multiply by 1000 and you have the remaining plant population. Often the corn stand is actually better than it looks from the road, so take the time to do some counts. It could save you some time and money.
Determine crop yield potential
Prior to May 20th replanting is a viable option if you have a corn population less than 24,000 to 25,000 plants per acre. After May 20th, only replant if your corn population is less than 20,000 plants per acre.
Removing a corn stand
Once you have decided to replant, a decision must be made about taking out the previous stand. Although it is tempting, it is not recommended to plant directly into the existing corn because the original stand of corn will compete with the newly planted corn and cause yield reductions.
There are only a few viable options for removing a poor corn stand in order to replant corn. Many corn hybrids have Roundup Ready and Liberty Link stacked traits, making removal difficult. If you planted single traits (either Roundup Ready alone or Liberty Link alone), you can use the other product to control the existing stand.
Most hybrids are stacked, requiring tillage or chemical control. Tillage has been effective at removing existing corn, and you can replant immediately. For chemical control, For those who cannot till, the best option is Select Max. There is a plant back period with Select Max of 6 days after application. Select Max should be applied at 6 fl oz/A with NIS at 0.25% v/v and AMS at 2.5 to 4lbs/A to corn that is up to 12 inches in height.
Gramoxone is often a first thought, but when applied alone, Gramoxone will not control corn. Research at other universities has shown that Gramoxone may be mixed with atrazine at 1 pt, Sencor at 3 oz, or Direx at 1 pt to improve control above 90 percent. I would caution against these mixtures for many of our coastal plains soils, and be sure to watch your atrazine rate because you cannot exceed 2.0 lbs ai/A (4 pt) in a season.
Information provided by Rod Gurganus, NC State Extension director in Beaufort County.