Yellowing corn leaves lower on the plant often signal a lack of nitrogen, but perhaps not this year.

Dry weather this spring caused problems with planting depths. Couple that with lack of moisture, and it affects brace root establishment.

“When we dig those plants up, there’s just not enough root development there to take up nutrients, and they're basically dying from the bottom up because they don't have root mass,” says Alex Long, a field agronomist for Beck’s Hybrids. The result is floppy corn syndrome.

In Missouri, spring planting was so dry that even getting seed into the ground was difficult. Long says that farmers indexed their planters right — 2- to 2½-inch depth — but with tough soil conditions, corn seed ended up three-quarters to a half-inch deep.

“You still see the effects of it today,” Long told a group during the first Beck’s Bash field day at Bay Research Farm in Columbia, Mo. “That leads to some of the yellowing you’re seeing in corn, and it’s getting written off as nitrogen.”

Actually, Long says, the yellowing may be linked to a potassium deficiency.

View below the surface

In corn, the first set of nodal roots, the brace roots, come out about 8 inches below the soil surface. Long says they are keyed off by light.

If seed ends up planted shallow — less than an inch deep — the nodal roots come out right at the seed. He says farmers will notice not only yellowing leaves, but also the plant “leaning pretty hard.”

“You have what we call rootless corn syndrome, or floppy corn syndrome, because it just doesn't have any stability,” Long explains.

While planting depth is one cause, others include:

Lack of moisture. Hot, dry conditions cause the upper region and surface of the soil to dry out quickly, especially in conventional-tilled fields. When nodal roots begin to develop and don’t encounter moisture, growth can stall, and the node set might die.

Open seed trenches. When the seed trenches are not sealed properly, then the depth setting set by the planter is less relevant to the plants. This is especially true if conditions are dry, and the seed slot reopens.

Corn genetics. While this is the least common cause for the syndrome, some genetics have a greater tendency for slower nodal root development.

Fix for floppy corn

The only way to remedy this syndrome is with moisture whether through rain or irrigation. However, Long says, farmers should assess the situation this year, then focus on the next planting season.

“Planting depth is one of the few things you have one shot at, and it's really tough to fix,” Long says. “You might as well be checking and making sure you’re getting it right.”