High Population Didn't Pay in Field-Scale Test

No benefit, some negatives, for going super-thick.

Published on: Dec 2, 2007

Maybe somewhere someone is showing yield benefit from 40,000 plants per acre compared to 32,000. But it certainly wasn't in the Corn Illustrated plots near Edinburgh, Ind. The plots were a Farm Progress Company exclusive project this year.

Dave Nanda, president of Bird Hybrids, LLC, Tiffin, Ohio, and consultant for the Corn Illustrated project, is crunching numbers and making final yield comparisons. One of the easiest conclusions, he says, is that going to 40,000 plants per acre in an attempt to boost yields even higher didn't pay. The actual seeding rate with the John Deere finger-pickup style planter last spring was just over 41,000 seeds per acre. That compared to 32,000 actual drop, the other rate in the high-yield trial. The host farmers, Jim, John and Ryan Facemire, typically drop 32,000 seeds per acre, particularly on irrigated ground.

The field where the high-yield test was planted consists of three feet of loam soil over pure sand and gravel. It's so pure that a gravel company actually purchased the farm a few years ago, looking to the future, and has actually removed gravel form a small portion of the farm not included nor not adjacent to the test. The field is irrigated, but for purposes of the study, about half was irrigated on time according to a computer-irrigation scheduler, about a fourth was irrigated beginning a week after tasseling, and the final fourth of the field was not irrigated at all.

The original goal was to reach 325 bushels per acre by finding the right combination of hybrid, seeding rate, nitrogen rate and with irrigation. Now Nanda says that may not be possible on these soils. The organic matter content is only around 2%. The highest individual six-row entry in the test yielded a bout 235 bushels per acre, dry corn, in the fully-irrigated portion of the test.

"Stress from heat hurt- there were roughly 41 days at Edinburgh of 90 degrees or above this summer," he says. "This is way above normal for south-central Indiana. In a more ideal year, we would have ended up closer to our goal. But it may not be possible under current production techniques and with today's hybrids to reach 300 bushels per acre on these soils."

Certainly bumping population wasn't the magic bullet. In some cases, actual yield for the same hybrid at 40,000 was less than at 32,000. There was also more lodging and more ear drop. The extra ear drop in the high-population plots wasn't from corn borer, but rather it's a result of stress on the plants, Nanda says.

Planting the extra 8,000 seeds per acre would cost about $12.50 for conventional hybrids. The hybrids in this particular test were not hybrids with traits. Spending $12.50 for little, no, or even negative payback doesn't make sense, Nanda says.

In fact, he thinks 32,000 may be higher than necessary in some situations. "Farmers ought to look at seeding rates carefully," he says. "They may be able to do just as well at slightly lower rates, depending upon where they are now, and save some money on seed in the process."

Look for full results from this experiment coming in the February edition of Corn Illustrated in most Farm Progress magazines.