Production Blog

Dig Out Your Best Corn Diagnostic Tool

Pamela Smith
By  Pamela Smith , Crops Technology Editor
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Digging some roots throughout the season tells a tale about whether the corn crop is worth pushing. (DTN photo by Pamela Smith)

Most farmers know exactly what it means to "spend more time on the business end of a shovel." While a shovel may be an icon of hard work, it is still the best tool to use for corn diagnostic work.

"The root system is the most important part of a corn crop, but also the most overlooked. A shovel is the best way to get an early read on the crop," said Steven Heightchew, an agronomist for AgriGold, in a recent news release.

He's referring to the fact that root development can guide management decisions. This season's weather curveballs are reason enough to do a little digging. Excessively dry or wet soils, insect damage, herbicide damage and sidewall compaction -- they can all stunt or restrict early root development.

"Evaluating corn as it's emerging gives farmers a scorecard for the rest of the year, showing whether they can push the crop to its maximum potential or whether the groundwork is laid for an average crop," Heightchew said.


Heightchew said checking unevenly emerged fields often reveals the radicle root has been injured by pests or chemicals. Even if there's not a problem, he urges growers to dig up a few plants early to see how that first root has burst from the kernel.

"To get things off to a solid start, we need the right root growth, the proper seeding depth, the crown to set at three-quarters of an inch and those roots to come out at 45-degree angles," he noted.

To assess root systems around emergence, Heightchew suggested digging a few plants in areas that are representative of the field. If there's a lot of variation within the field, you may need to evaluate those areas separately, he added.

Gently digging up the corn as it is spiking or in the early V-growth stages can provide clues to whether there were issues during planting.


Do another check around the V3 to V4 growth stage or about ruler height, he recommended. This is when the plant is shifting from its seminal root system to its nodal root system for nutrient uptake.

"The fibrous roots should start at that 45-degree angle and branch down through the soil to get the depth needed for water uptake if dry conditions develop," Heightchew explained. "For the corn factory to thrive, it needs to have big, deep roots to pull up water and nutrients.

"Think of those roots like a straw in a milkshake," Heightchew said. "With a small straw, you'll have trouble pulling the milkshake up out of that cup. But if you use a bigger straw, it's easier."

If there's adequate soil moisture, a good 45-degree root set and no compaction, Heightchew said that's the green light farmers need to apply additional inputs and push yields.

If roots start turning to go out rather than down at that 45-degree angle at the 3- or 4-inch mark, that indicates you have compaction lower in the soil -- likely due to tillage, he added.

"When that happens, farmers should focus on having nutrients available in those top 3 to 4 inches," Heightchew said. Water availability will also be key.


It's hot. The pollen is starting to fly, but don't put the shovel away yet. Around tasseling is the best time to check to make sure corn rootworm controls are working. Root damage from corn rootworm is highest when most larvae have completed the third larval stage. Digging roots too early before larvae have completed development can underestimate the potential total damage. Roots dug after most adults have emerged are often more difficult to wash and rate.


Keep your boots dirty as the summer rolls along toward fall, Heightchew recommended. If those early yield estimates taken prior to harvest aren't to your liking, start digging again.

"Even that far into the crop cycle, you can usually pinpoint what went wrong by looking at the roots," he said.

Besides a shovel, Heightchew likes to see farmers use a penetrometer to measure soil compaction. Don't have one? Make do with a sharpened piece of rebar, he suggested.

"You just need something you can push down into the soil to see if there are restrictions. If it pushes through the soil easily, that's good. But if you face resistance, so will roots," he said. Evidence of compaction indicates a need to work on soil health and evaluate magnesium levels.

As spring wears on, there's often a rush to try to get ahead of another rain. Those decisions can be difficult and not clear-cut.

"Rooting starts with the planter pass. Taking the time to make smart decisions and place seed right will give you better yields overall," Heightchew said. "Balance is the key."

And leaning on the shovel to evaluate what management steps come next.

Learn how happens when corn grows fast in this DTN article:….

Find a DTN article on how to do a root dig for rootworms here:….

Want to contact an AgriGold agronomist? Go here:….

For more information on corn roots and how corn grows go to:






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