The formula for estimating corn yield requires counting the number of ears in 1/1,000 of an acre. In 30-inch rows, that’s 17 feet, 5 inches. When Dave Nanda does yield estimates, he counts the number of ears on either side of a rope marking off 17 feet, 5 inches. But he goes back and counts the number of barren plants within that 1/1,000 of an acre on each row and records those numbers, too.

That number doesn’t go into the yield formula, but it’s an important piece of information, Nanda says. Each barren plant or plant with a nubbin that doesn’t count as an ear took up space for a plant that should have produced an ear.

Related: Factor in less-than-ideal spots when estimating corn yield

“Each ear in 1/1,000 of an acre represents about 7 bushels per acre,” says Nanda, director of genetics for Seed Genetics Direct, the company that sponsors Corn Watch ’21. “If you have two barren stalks in 1/1,000 of an acre, you could have gained another 14 bushels per acre if they had produced normal ears.”

Determining causes

The leading cause of barren stalks in most fields is late emergence, Nanda says. A plant that doesn’t produce an ear likely came up so late compared to neighbors that it was shaded out and became a weed, taking up nutrients that could have gone to neighboring plants but contributing no yield.

“When that happens, that corn plant is worse than a weed,” Nanda contends. “You can take out weeds with herbicides, but you can’t remove a late-emerging corn plant by any practical method.”

Some say a plant only must be one to two leaf collars behind in emerging to turn into either a barren plant or one that produces half an ear. There is some evidence to indicate that the equation may not be that simple. If a series of plants within a row all emerge late, they may not be affected the same way as if only one plant emerges late while its neighbors come up on time.

There was indication in the 2020 Corn Watch project that if a field were planted early and it turned cool, plants emerging up to a few days later may not be as affected as you’d think because the first plants to emerge weren’t growing at the normal pace. This year’s Corn Watch field will test that principle because some rows featured long delays in emergence. Look for more on this year’s results once harvest checks for yield are made.

Nanda says plant spacing also enters the equation. If a late-emerging plant is 8 to 10 inches away from another plant in the row, the impact may not be the same as if the late emerger had a neighbor just 6 inches away on either side.

When growers push populations too high, barren plants sometimes show up as well. In that case, the stress of high population may lead to a higher percentage of barren stalks.

“It’s important to determine why you’re seeing barren plants and try to correct it,” Nanda concludes. “Barren plants represent wasted energy and a lost opportunity to add another 7 bushels per acre for each plant without an ear.”