This is the second year in a row where the farmer opted to replant into the existing stand in part of the Corn Watch field because of poor emergence. Lightning struck twice!

The conclusion a year ago was that using that option rather than tearing up the stand likely paid off. The problem with tearing up the stand was a later planting date by three to four weeks. The situation was similar in 2017, with a large gap of nearly a month between the first planting and a replant opportunity.

In areas of the field where stands are very thin, say 10,000 to 15,000 plants per acre, adding plants tends to up yield potential. Dave Nanda, an independent crops consultant based in Indianapolis, says that works where gaps are large enough to allow plants from the second planting to emerge together and have each other as neighbors. When plants within an area emerge at the same time, they typically compete well with each other.

Downside
The problem with replanting into an existing stand comes when the original stand is thin in some areas but better to even near the intended plant population in others. With large 12-, 16- and 24-row planters, it’s nearly impossible to avoid replanting in some areas that still have a good stand in some rows. Most farmers who have replanted into existing stands report that they make decisions to turn the planter on and off manually, based on what they see.

Some planters may have the capability to shut rows on and off, but mapping fields and creating a prescription for replanting into an existing stand isn’t a high priority. It’s something you hope you don’t have to do very often — let alone two years in a row!

Plant competition
“What we noticed this year was that in areas where there was still a pretty good stand from the first planting and plants from the second planting were very close by, ear size was extremely variable,” Nanda says. “There were still decent-sized ears on the first planting, but spindly stalks which came up later from the second planting tended to produce small ears to nubbins.”

Even small ears from the second planting will contribute to yield, Nanda says. But here’s the rub. Will they contribute enough to offset the sunlight and nutrients they took away from existing plants? Could the existing plants have produced even better ears with more kernels if the later plants weren’t there?

“I’m convinced that in many spots, the later-planted replant acted like weeds,” Nanda says. “My guess is they may hurt overall yield.”

The bottom line is that deciding to replant, and choosing whether to tear up the stand and lose planting-date gains or to replant near existing rows, is one of the toughest calls in farming. Corn Watch ’17 is sponsored by Seed Genetics-Direct, Washington Court House, Ohio.