Right Population to Plant Remains a Mystery

Solve it for your own farm on a farm-by-farm basis.

Published on: Feb 4, 2008

Visit about any seed corn meeting this winter and you are likely to hear that one of the keys to higher yield is to increase plant population. That somewhat depends upon where you’re starting point is. But a large regional company insists at their winter programs that trend yields are still going up for most hybrids at planting rates of 33,000 seeds per acre. Or at least that’s what they discovered last year.

Yet the value of higher population wasn’t so clear cut in the Corn Illustrated plots last year. This exclusive project sponsored by Farm Progress Companies included both irrigated and non-irrigated plots on an actual farm near Edinburgh, Ind. The high-yield experiment in the plot featured corn at 32,000 and 41,000 seeds per acre. Checks at harvest indicated that populations were close to those levels. Part of the plot was irrigated and a small section was not irrigated.

The overwhelming conclusion from that study was that pushing population too high actually decreased yields, even on the irrigated land where ample moisture was available during the entire season. It was also a hot summer, however, with nearly 41 days of 90 degrees F or higher at the site.

Pushing to 41,000 under those conditions, even under irrigation all season long, resulted in ear drop of a significant amount on the thickest plots. When the yields were totaled, the 32,000 plots were the winner in about every category. The plot included three different hybrids in various comparisons, and also included corn sprayed with Headline fungicide vs. corn not sprayed with fungicide.

Dave Nanda, president of Bird Hybrids LLC, and consultant for the Farm Progress Corn Illustrated plots project, firmly believes you can push corn populations too high. Despite what others are showing, he believes that it may be possible to hold down seed costs by cutting back on seeding rate, without damaging your yield potential. Naturally it partially depends upon your starting point, ie- what rate you typically plant at today.

Nanda recently advised one of the farmers he works with who farms moderate to low organic matter soils that he would cut back from 32,000 to 30,000 seeds per acre this year, even on his better soils. That will save him about $5 an acre, Nanda says. And Nanda is confident that cutting back and keeping the extra $1,000 in his farm account will not hurt him when he takes the combine into the field for harvest next fall.

It’s important to note the conditions where any test was run when you hear reports at meetings or read them in company report books from last year, Nanda advises. If the test was run on very high organic matter, central Corn Belt, deep, well-drained soil, it may not guarantee that you can produce the same kind of results using the same practices on your farm, wherever it might be.
Someday everyone may plant 60,000 to 70,000 seeds per acre, Nanda says. Her firmly believes it. But it will likely be with equipment that spaces corn at equidistant spacing one to another plant. And it will be with hybrids developed to handle such high populations. Mushrooming seed costs for going to such a high seeding rate should be offset by much higher yields. He believes that when seeding rates finally reach that level, 400 to 500 bushels per acre will be feasible, especially on better soils.

In the meantime, reality is equipment that doesn’t space every plant an equal distance form another, and hybrids that while very advanced, aren’t adapted to growing at such high populations. That’s why he questions whether it’s even necessary to go as high as many companies recommend. In the end, you’ll have to weigh what you’ve seen work on your farm, and determine if you can cut back safely, saving on seed costs, without jeopardizing the highest possible economic yield.