Bob Nielsen believes that if farmers knew a little more about how corn roots develop and work, they would understand when the roots reach critical stages, and what they can do to protect or enhance them. Nielsen is the Purdue University Extension corn specialist.

Learn about the basics of corn roots through these common questions. Perhaps you have asked them yourself. Nielsen provides the answers.

To learn even more and see a set of pictures Nielsen has assembled about corn roots, visit kingcorn.org.

Corn has primary and secondary roots. Is that correct? Yes, but it can be confusing. The seminal root system, which develops first, is also known as the seed root system. Many people also call it the primary root system. The nodal root or crown root system develops next and is classified by scientists as the secondary root system. It makes chronological sense. However, in terms of importance to the plant, the nodal root system is clearly the primary root system. It carries the plant through the season.

Can damage to the seminal root system affect yield? Yes. The radicle root emerges first, rupturing through the seed coat near the tip end. It first elongates in that direction, no matter which way the tip is pointing. Lateral seminal roots emerge behind the coleoptile and initially elongate toward the dent end. However, soon both sets of seminal roots respond to gravity and elongate downward.

Early damage to the radicle or lateral seminal roots can stunt initial seedling development, even though the seminal root system contributes little to season-long maintenance of the plant. If these roots are damaged, the plant may not die, but it may cause delayed emergence. It can also cause leafing out underground. So, you either get a late emerger, which contributes less to yield, or a plant which never emerges at all.

What can damage the seminal roots? Postgermination injury from lethal or sublethal soil temperatures could be an issue. Salt injury from too-high rates of starter fertilizer placed too close to the kernel will also cause damage.

What does early root damage look like? Symptoms include retarded root elongation when you dig up a seedling trying to emerge, and brown tissue discoloration. You may also see prolific root branching and outright dead root tissue.

If the radicle root is destroyed, will the plant die? Not necessarily. If the lateral seminal roots are healthy, growth could continue. However, what’s likely to happen is that the coleoptile will split and leaf out underground. At best, you’re going to have a later emerger, which contributes little or nothing to yield.

When can you see the first nodal roots? Nodal roots develop from individual nodes above the mesocotyl. When the collar of the first leaf is visible, you can identify the first set of nodal roots by a slight swelling at the lowermost node. By late V1, you can see the first nodal roots have elongated. They’re clearly visible by V2, and the second set of nodal roots begins elongating from the second node.

When does soil compaction become an issue for roots? It is clearly an issue if tillage compaction or sidewall trench compaction stunts or restricts nodal root growth. It can stunt the entire plant. When diagnosing causes of stunting, start below ground.