Every farmer knows the frustration: a field shows all the signs of impressive yields, but harvest tells a different story. The kernels were there, but grain fill didn’t reach its potential — or late stress triggered kernel abortion. Maybe you saw it this year.

Key Takeaways:

• Many bushels are still on the line during corn’s post-pollination growth stages.  
• Nutrients like potassium, boron and sulfur can help the crop finish strong.
• But whether the ROI is there will vary by crop and by season.

As you evaluate this year’s crop and grain fill, now is the right time to start shaping next season’s fertility plans — for the start of the year and through grain fill. For corn with high yield potential, fertility during the reproductive stages can help capture those extra bushels, pushing yields from good to great.

In addition to at least one foliar fungicide application, LG Seeds Agronomist Landon Taylor says growers looking to maximize corn yields should also consider three key nutrients during corn’s reproduction stages: potassium, boron and sulfur.

When late-season management is worth the investment

Discussing his Mid-South geography, Taylor shares, “In my opinion, fungicide isn’t optional, but boron and sulfur should be a season-by-season decision that considers market prices, economics and the potential for a return on investment.”

Growers should also evaluate their crop when debating in-season inputs. “Don’t spend more money on nutrients for a field that’s not up to par, whether your stand isn’t there or ears aren’t consistent,” Taylor says. “But if a field is looking promising, take advantage of the opportunity.”

It’s also worth noting that some hybrids are more responsive to intensive management than others. Knowing what you have in your fields and how best to manage them can also help with that decision-making.

One that stood out for Taylor this season for its response to high-yield management as well as its ability to handle heat is  LG67C07. This product, which Taylor deems “King of the South,” has a good disease package and responds well to high management, with the ability to flex its ear in many environments. “It’s the whole package,” he says. 

“It took a pollination period marked by hot days and warm nights in stride,” Taylor continues. “The deep green product has lower ear placement and broad leaves that help keep the canopy cooler, which can make a difference in a season marked by heat. We’ve seen a lot of tip back this season, but LG67C07 had no trouble filling ears to the tip.”

Say yes to corn fungicide

“If you ask me whether to spray a fungicide on your corn, my answer will almost always be yes, because a significant portion of corn’s yield has yet to be made,” Taylor says. “Fungicide can help keep plants healthy, so they are able to fill out and protect those kernels.”

Before making an R1 application, he encourages growers to identify their main disease threat(s) and use that information to choose their fungicide. An agronomist can also provide support with this decision.

If crop prospects are promising and the economics make sense, growers might consider adding some fertility to their fungicide applications to bolster corn’s grain fill.

Potassium: Essential to water movement in corn

Potassium is key for corn during the reproductive phases. “Potassium is the corn plant’s main lifeline for water transpiration and movement through the plant. It aids in water uptake and helps the plant fight off diseases that might threaten stalk integrity,” Taylor explains.

In Taylor’s territory stretching from Kentucky to the Delta, high temperatures and drought stress the latter part of the season has corn plants scavenging for water. In that environment, potassium can make a substantial difference.

“Having adequate potassium allows the plant to rest,” he explains. “It is important for plant translocation, or the moving of sugars and nutrients through the plant. And hopefully you catch a rain.”

Sulfur: Significant uptake during corn’s R stages

It might surprise growers to learn that corn takes up more than half of its sulfur needs during grain fill, according to a report from The Sulphur Insitute¹ — quite a few weeks after growers typically apply this nutrient.

To make sure sulfur is still there to help corn form and fill kernels, growers can spray a relatively small amount of sulfur late in the season. The leaf is the primary source of food for the kernel during this point in the growing season, so that mode of application is more efficient, according to Taylor.

Boron: Best when spoon-fed throughout the growing season

Boron is important to the corn plant all season long. In the latter part of the season, it helps keep silks viable during pollination and facilitates the movement of sugars from the corn leaves to the ears for kernel fill. 

This key nutrient isn’t mobile, meaning supplemental doses of boron are needed to maintain nutrient availability. “If boron is only applied upfront, it could be gone when the plant needs it later in the season,” Taylor explains. “Boron works best when a little bit is applied many times.” 

As you pull soil samples this fall and think through corn fertility program options for pushing yields to the next level in seasons to come, reach out to your local LG Seeds agronomist. Our in-field expertise and ongoing agronomic training ensures you get the latest strategies for optimizing crop performance and guidance tailored to your farm.

^{1. The Sulphur Institute. Is Sulphur the missing ingredient? Sulphur. January-February 2021. 392;1-3. https://www.sulphurinstitute.org/pub/?id=be62aa02-1866-daac-99fb-4ae5712bf1c7.}