Going deeper can bump corn yields

When it comes to planting depth, deeper is most often better.

More producers like Dan Gillespie of Meadow Grove are planting corn 2 1\2 inches deep to get a more developed root system and more uniform stands.

Gillespie made the switch from 1 1\2 to 2 1\2 inches about three years ago in his no-till corn. “In 2009, it was the best stand I’ve ever had and better yields as a result,” he says. “Uniformity of emergence means more uniform ears and plants, and thus better yield potential.”

Gillespie plants some of his corn crop into fall-seeded cover crops. “Even when we encountered a bit more drying of the soil under the cover crop, 2 1\2 inches worked well. It got us down to the better soil moisture.”

Mark Watson, a no-tiller from Alliance in the Panhandle, also planted at the
2 1\2-inch depth on some of his heavier soils. “The deeper depth increased our corn yields,” he says.

At a glance

• Planting corn too shallow leads to emergence problems.

• Most planters are designed to plant corn 2 to 3 inches deep.

• Research and farmer experience shows higher corn yields.


There’s a general attitude that planting shallower makes for quicker emergence, according to Paul Jasa, University of Nebraska-Lincoln Extension engineer. Also, in the past two years, cool, wet spring conditions prompted farmers to plant shallower, 1 to 1 1\2 inches, again hoping for quicker emergence.

That goal may have been achieved, but they run the risks of other problems, especially with non-uniform emergence, says Jasa.

Most corn planters were designed to plant 2 to 3 inches deep, so the plant develops a good root system. “When planting shallower than that, especially when using a planter with angled closing wheels, you risk creating sidewall compaction as the press wheels compact the soil below the seed rather than around the seed,” Jasa adds.

Moreover, with shallow planting, the press wheels may not properly close the seed-vee, allowing it to dry out, which affects germination or root development.

“Problems may be blamed on insects or herbicide injury, but actually result from planting too shallow, so scout carefully to determine the true cause of problems,” Jasa says.

Planting deeper will put the seed in slightly cooler soil, but the soil temperature at that point is more uniform and buffered from low nighttime temperatures, resulting in more uniform emergence. If cool soil is a concern, use a pop-up starter, Jasa recommends.

“When corn is planted too shallow, ‘rootless corn syndrome’ may develop as the nodal roots don’t form properly if the soil surface is hot or dry,” he adds.

Citing UNL plot studies, Jasa made the following observation: “Two-inch depth always beats 1 inch in yields, and 3 inches usually beats 2 inches.”

Soybeans

“If soybeans are planted shallow into cornstalks, you may be placing the beans in root balls,” he says. “That’s why I would go deeper, about 2 inches, with beans.”

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SEED DEPTH: Planting corn 2 1\2 inches deep leads to a more uniform stand.

This article published in the February, 2010 edition of NEBRASKA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.