Hopefully you won't have to worry about replanting corn this year. A sizable number of acres are in the ground now. In many areas, light rains fell that should have been gentle on planted fields. What happens now may depend upon how quickly it warms up and stays there.
Nevertheless, nearly every year there is a 'wrong day to plant.' You just don't know when it is until it's too late. If you get stuck with a field you planted in that category, the nasty word 'replant' may dance in your head. Crops consultants say many times it's best to do a lot of counts and checking before you decide to bring in the disk and start over, even if the stand is much less uniform and not as thick overall as you would like.
Here's an example based on numbers collected and published by Bob Nielsen, corn specialist at Purdue University. If you planted April 25 at 32,000 seeds per acre, and end up with an average stand of 19,500 plants per acre, what should you do? Realize that 'average' includes spots of 6,000 plants per acre and areas of 32,000 plants per acre.
If the 6,000 per acre spots are in one block, you could likely replant that block. But that's not real world. They're likely scattered.
What you do may depend upon when you decide you're looking at all the corn that is going to emerge. And remember, reminds Dave Nanda, a consultant, that late emergers within the row may act like weeds anyway, actually detracting from yield instead of adding to it.
If it's May 15, it may be one thing. If it's June 1, it's another. In fact, if it's June 1, even if you get a perfect stand on replanting, you will only expect 82% of normal optimum yield most year. Last year was not most years, when late planted fields did very well. If you leave the 19,500 stand planted April 25, you can expect 91% of actual yield. So in that case, leaving the stand would be a no-brainer.
Other considerations come into play, including how expensive replanting will be. Some companies provide replant seed free, some don't. And if there is not sufficient crop canopy, there may be more weeds, requiring more weed control.
Whatever you do, make the decision based upon data and numbers, not emotion. Tractor operators driven by emotion have disked up many stands that would probably have made them more money if left alone.