Figuring Corn Seeds Per Acre

The number of seeds planted per-acre in a corn field has been increasing annually over the past two decades. Much of this is because plant breeders continue to improve the overall stress tolerance of hybrids, and high plant populations do represent a type of stress.

Bob Nielsen is an agronomy professor at Purdue University. He says their research is showing that corn eventually reaches a plateau.

"At the lower side, as you increase populations you get a pretty strong yield response. But as the population gets closer and closer to the optimum, the yield response begins to taper off, and ultimately it just basically plateaus," he says. "And once you reach the optimum agronomic population, adding more plants simply does not increase yield, and at some point, will actually decrease yield."

Because those last thousand-seeds-per-acre-or-so result in so few bushels, the economic optimum ends up being less than the agronomic optimum.

"Our agronomic optimum, for example throughout much of Indiana, is a final stand of somewhere around 32,000," he says. "But because of that response curve and with grain prices being what they are and feed costs being what they are, our economic optimum tends to be below 30,000 for many of our soils here in Indiana."

Knowing the history of successful stand establishments allows you to convert plant populations to seeding rates. Nielsen says with today’s planter technologies and seed quality, aiming for a percent stand of no less than 95% is a realistic goal.