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Didn't Plant a Monster Seed Population? Don't Worry

Hindsight may be 20/20, but that doesn't mean decisions based on hindsight are the best. That's especially true with corn plant populations, one expert says this week.

There's been some discussion in Emerson Nafziger's state of Illinois lately about how this growing season -- one that's got some cornfields flirting with record or near-record yield potential -- could have supported plant populations up to 45,000 plants per acre. It "could have" worked, yes, but would it have been a sound agronomic decision?

"The assertion [is] that 45,000 plants would have been more appropriate than 32,000 plants. Most producers are planting more than 32,000 now on more productive fields. But few are pushing populations into the mid-40,000 range, at least, on a lot of acres," says University of Illinois Extension agronomist and corn expert Emerson Nafziger. "Did we all miss the boat by planting 'only' 35,000 or 36,000 seeds this year?"

Sure, planting 45,000 seeds per acre will raise your yield potential. But will it raise it enough to justify the additional expense of the extra seed?

"On average, the difference in yield between these two populations was only about a tenth of a bushel, and there was no indication that the response got larger as yield level increased. In fact, the line drawn through the points shows slightly lower yield differences as yield level increased," Nafziger says on the yield data for 34,000 seeds per acre vs. 42,000. "At yield levels lower than 150 bushels per acre, 42,000 plants yielded 9 bushels more than 34,000 plants, with a range of -62 to +48 bushels. At yields above 250 bushels per acre, 42,000 plants yielded a half bushel less than 34,000 plants, and the range was -24 to +24 bushels. This reinforces what many of us know -- that low-yielding conditions tend to make yield less consistent, with more differences due to factors like hybrid stress tolerance water-holding capacity within fields."

Generally, this makes that high-end population a nonstarter in most circumstances. Instead, it's more reasonable to stick to a more typical population from 30,000 to around 36,000, both in terms of prospective yields and the increased risk associated with a higher plant population.

"These data give no support to the idea that a corn crop planted at populations in the mid-30,000 range is incapable of taking full advantage of high-yielding conditions. The data also confirm that risks of having populations too high for the conditions increases when we don’t have conditions for high yields," Nafziger says. "Because we don’t know what conditions will be at the beginning of the season – the 2012 season started off great and would have been a 'good' season to raise populations at planting -- it makes no sense to push populations above 40,000 in hopes that we'll get the weather to make this pay off. In fact, the response of yield to population tends to be fairly flat over the range of the lower to the upper 30,000s, regardless of yield level or conditions."

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