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Read Your Crown Roots

August 24, 2013
By: Rhonda Brooks, Farm Journal Seeds & Production Editor
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Dig up corn to put more money in your pocket

Drive by Leon Knirk’s farm one day this fall and you might catch sight of him digging up corn plants with a shovel. No, he hasn’t lost his mind. He’s in the process of evaluating what he refers to as corn’s money roots—the first, second and third set of crown roots.

These three sets of crown roots supply the bulk of nutrients and moisture to corn, making them essential for high corn yields. Their appearance tells Knirk a story he can read in 30 seconds or less. In that brief span of time, he sees the impact his tillage program has had on his corn crop’s growth and development. If the money roots are growing like they should, the Quincy, Mich., farmer can anticipate harvesting more corn this fall. The opposite is true, too, if his tillage practices have created a density layer—a zone of packed dirt beneath the soil surface that can extend horizontally across a field and impede corn-root growth.

Corn roots are designed to grow down deep into the soil at a 35° to 40° angle, says independent agronomist Bill Bauer, who led a session on the topic at the Farm Journal Corn College Fundamentals event in Michigan. He says if there’s no obstruction—no compaction and no density layer—corn roots grow vertically as long as they have access to water and oxygen. However, if the roots hit an obstruction, they will turn and grow horizontally, or sideways. "When we’re turning a lot of roots, that puts limitations on the crop," he says.

When roots turn and grow sideways, the corn plant is unable to effectively absorb nutrients and moisture that might be deeper in the soil profile as summer progresses. This results in less productive plants that are vulnerable to pests, disease and standability issues.

"There’s no sense in spending money to increase nitrogen or push populations for higher yields in a scenario where plants are hitting a density layer because they can’t respond the way you want them to," Bauer explains.

Farmers who run a disk or field cultivator in poor conditions don’t realize the negative impact those tools have on soil structure below ground. Corn yields can suffer significantly as a

result, says Brad Beutke, who also presented at the Corn College event.

"In extremely wet or dry years, when a horizontal density layer has its greatest impact, we’ve seen 70- to 80-bu. differences in those fields compared to fields where the roots can grow down like they’re supposed to," Beutke adds.

In Bauer’s experience, shallow density layers, within the top 4" are more detrimental to yield than layers deeper in the soil profile. He tells farmers to use a tile probe to get an idea if a density layer or obstruction is present.

"Make a note of anything that stops your probe," Bauer says. "It might be a density layer you hit."

Bauer tells farmers when they dig up the corn plant to insert their shovel outside of where the planter gauge wheels ran; then dig 8" to 9" deep all around the plant. "If a density layer is present, the soil will naturally want to break at that layer, so you’ll know that’s where the problem is," he says.

Harvest priorities. Potential density layers are what Knirk looks for when he evaluates corn crown roots late in the season. Hybrids affected by them almost always have endured moisture and nutrient stress, which result in premature stalk cannibalization.

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FEATURED IN: Farm Journal - September 2013
RELATED TOPICS: Agronomy, Corn College, Production

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