How Thick To Plant Still a Hot Topic

Issue still white-hot as planting approaches.

Published on: Feb 16, 2009

How many times can you write about what planting rate is best for corn? Apparently, the sky seems to be the limit. Everyone has an opinion, and both brand new data and data summaries seem to continue flowing in form all directions.

Some of the latest reports coming from agronomists tend to be coming to this conclusion after evaluating recent data- achieving 30,000 plants per acre is an ideal place to be. At some point above that, yields level off and eventually even drop. Go too far below it, except on low organic matter soils or in very stressful years, and yields will fall short of the goal too.

Our Corn Illustrated plots came out at plant populations of 26,000 to 27,000 producing the best yields in '08, but that was on low-organic matter soils where too much rain fell early, then too little rain fell late. Jeff Phillips, Tippecanoe County Extension age educator and a researcher by training, discovered in replicated tests that 30,000 seeds per acre seemed to be about the ideal spot. He used the same hybrids used in the Corn Illustrated test last summer. However, he worked on higher organic matter soils near West Lafayette, on the Purdue University Throckmorton Research Farm.

"More and more people are saying 30,000 plants per acre is ideal," says Dave Nanda, a plant breeder and president of Bird Hybrids, Tiffin, Ohio. Nanda has also been closely involved with the Corn Illustrated project sponsored by Farm Progress Companies for the past two years.

"That fits well with what many seed corn companies have been saying for a long time," he adds. Pioneer Hi-Bred, International, for example, ahs talked about that goal as a good place for farmers to zero in on for a long time.

"We know that based upon the hybrids we raise today and the genetics available, if we go too thick we can actually hinder yields," Nanda says.

He notes, however, that the distinction between plants per acre and seeds planter per acre is a big one. "We typically talk about plants per acre when we're comparing how one rate performed against another," Nanda notes. "If you want 30,000 plants per acre, you typically may have to seed and extra 1,000 or more seeds per acre, even with today's best planting equipment."

He also noted that in the Corn Illustrated population trial in '08, one of the hybrids, a smaller-seeded hybrid, tended to overplant. "Sometimes we counted more stalks per acre than we were supposed to plant seeds per acre," he recalls. That emphasizes the need for understanding how various sizes and grades plant in your particular machine, he notes.

It also points out how important it is to check seeding rates when you start planting, Nanda says. You may be able to tell with sophisticated monitors. But the plant breeder in him still prefers planting a strip, then digging in the soil to determine both seeding rate and seed placement.