Ferrie: If You Want Agronomic Answers, Read Your Crown Roots

Across parts of Illinois this week, Ken Ferrie is seeing some impact the “sins of spring” are having on farmers’ corn crops.

These so-called sins are practices that contribute to a less-than-ideal corn stands. A common one is horizontal tillage.

“That contributes to around 90% of the compaction issues we see,” Ferrie says. 

“Any compacted fields, fields with wheel tracks in them, sidewall smearing…they’re all now showing themselves,” he says. “If this is happening in one of your fields, it may be talking to you and telling you to come take a look and identify which of the sins of spring is causing the problem – that's how you’ll be able to fix it for next year,” he adds.

Here are three additional considerations from this week's Boots In The Field Report:

1. How Field Diagnostics Can Help
Ferrie encourages farmers to dig up corn plants now and evaluate crown roots. They can tell you a lot about what caused the problem, how serious it’s going to be and how challenging it will be to address.

“Dig good and bad plants in multiple areas of the field, and compare them,” Ferrie says. “Crown roots should come off the stalk in a circular pattern, growing downward at about a 30˚ to 35° angle.”

The first, second and third sets of crown roots (1, 2 and 3) are very important for yield.

“The first three sets of crown roots are the big dogs. They supply the bulk of nutrients and moisture to corn, making them essential for high corn yields,” Ferrie says. 

The fourth and fifth crown roots (4 and 5) are generally more for support and anchoring the plant, sometimes above ground (brace roots). While important, roots 4 and 5 are less of a factor on yield than crown roots 1, 2,and 3.

If there’s no obstruction—no compaction and no density layer—corn roots will grow down 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.

Check out what three farmers say are their biggest corn yield bandits: Perform a Crop Autopsy to Identify Your Top Yield Robbers

2. Sulfur And Nitrogen Deficiencies Are Evident This Season
Because of dry weather, many corn crops are struggling to tap into adequate nitrogen and sulfur now. The two problems look similar at first glance, but there are key differences you can observe, says Ferrie, Farm Journal Field Agronomist.

"Nitrogen (N) deficiency shows up in the older leaves at the bottom of the plant. Sulfur (S) deficiency shows up in new growth—at the top of the plant or in the whorl of corn plants. That’s because plants can move nitrogen from the old growth to the new growth, but sulfur, unlike nitrogen, is not mobile," Ferrie explains.

Sulfur is incredibly important to corn production – a bushel of corn removes 0.08 lb. of sulfur in the grain and 0.09 lb. in the stalk – 0.17 lb. total. 

"A 200-bu. corn crop takes up 34 lb. of sulfur per acre," Ferrie says. “That figure is even more impressive if you think of it in terms of sulfate, which is the form of sulfur that plants actually can use—102 lb. of sulfate per acre.”

In crop production, sulfur’s most critical job is helping produce protein molecules and amino acids, which are required to produce chlorophyll, lignin and pectin. To do that, it assists in photosynthesis, the process in which plants convert sunlight into chemical energy.

Another key benefit to not overlook is that sulfur helps metabolize nitrogen. More insights on N use in-season are available here: Are You Underestimating the Value of In-Season Nitrogen Use?

"If a tissue test reveals a sulfur deficiency, it probably will show a nitrogen deficiency, as well," Ferrie says. "Both are structure-building components, so sulfur (like nitrogen) is required early in the season. The plant needs sulfur to build the factory that will produce the fruit."

Insufficient sulfur results in stunted growth and can delay crop maturity.

“Under the concept of never let corn have a bad day, corn showing a sulfur deficiency is having a bad day,” he says. “This is especially true for those G and L1 hybrids that will flex down if you stress them in that window before tassel and soon after emergence.”

He notes that Y-dropping sulfate next to the row can improve sulfur (sulfate) performance. “We need to go early on small corn, which means we need to go slow and not splash product on the small corn plant and cause burn. This is a recommendation for higher organic matter soils that only have a temporary sulfur problem early in the season,” he adds.

Sandy soils might need a different strategy. In sandy, leachable soils, farmers need to consider putting together a program that keeps the corn plant supplied with sulfur all season and not just up until V10, Ferrie advises. 

Learn more about addressing sulfur in-season here: Seize Your Corn Yield Potential With Sulfur's Amazing Superpowers

3. Herbicide Carryover
There is some carryover damage from 2022 showing up in corn now. While the crop will shake it off with time, there could be some yield loss resulting.

“This problem goes back to the dry June we had last year that didn’t allow the herbicide to break down before this season,” Ferrie says.

Dry conditions days and weeks after a herbicide application can push out the product’s half-life. It’s also common for little herbicide breakdown to occur in the winter. That combination contributed to this season’s issues.

Those concerns are also reasons why Ferrie says farmers should consider doing a grow-out this next winter to assess potential herbicide carryover in fields before the 2024 season. “It’s likely we’ll see this problem again next season,” he says.

Ferrie adds that though the growing season has gotten off to an uneven start, stay the course with your crop. 

"We have a saying around here: You never walk away from a crop,” Ferrie says. "Giving up usually gets expensive. It’s best to stick it out and do what you can to manage the hand Mother Nature has dealt you.”

To hear all of Ferrie’s agronomic recommendations in this week’s Boots In The Field, listen here: