Production Blog

This time of year, we tend to analyze the upcoming corn crop like an NFL coach heading to the Super Bowl. With the trade calling for a monster crop in 2025, every kernel -- or lack of it -- is ripe for conjecture and the term "tip back" is on the tip of everyone's tongue.

Grain that doesn't fill the ear is a legitimate concern this year, according to Dana Harder, an agronomist who covers Missouri and west-central Illinois for Burrus Seed. He provides six explanations for why ears might fall short of filling completely, but sees a common thread this year.

"Most of the tip back I have seen this year has aborted kernels present, meaning it went through stress shortly after pollination," said Harder. While some areas suffered drought, he's more inclined to blame elevated nighttime temperatures for the stress.

"I think there are going to be some surprises when we harvest this crop. Even those farmers who had fertility and populations dialed in to their APH (average production history) and had adequate moisture are finding aborted kernels when they check ears," Harder said.

Another thing to keep in mind is that a little tip back is actually a good thing. "Anything under one-half inch means you're pushing population on those products to just the right level," he said. "But in some instances, this year, we're seeing a good two inches missing."

"Production selection and other good management practices can help manage tip back to some degree, but ultimately Mother Nature is in control," Harder said. "The goal now is to hang on to what you've got, and hope conditions allow the ear to accumulate dry matter," he added.

Here are six factors that can cause barren tips, according to Harder.

-- No. 1: Stress at Pollination

Drought stress during pollination can delay silk emergence. Since ears pollinate from the base working to the tip, the kernels at the end of the ear are the last ones to pollinate. If the silks attached to the tip do not emerge until after pollen shed has ended, pollen will never reach them, resulting in tip back. This will look like there is an empty cob sticking out at the end of the ear with no kernels on it.

-- No. 2: Stress Following Pollination

Aborted kernels show there was successful pollination, but the plant decided it could not support all the kernels that were pollinated. Any stress that limits the amount of energy in the plant in the period immediately following pollination can cause kernels to abort, starting at the tip and then working their way to the base. The final kernel number is determined 18-20 days between pollination and the R3 growth stage (milk stage).

-- No. 3: High Nighttime Temperatures

If the temperature doesn't drop below 70 degrees Fahrenheit at night, the plant will not have adequate time to recover from elevated daytime temperatures. Respiration rates will stay elevated throughout the night, wasting energy needed for kernel fill.

-- No. 4: Too Little or Too Much Rain

Too much or too little water will cause a plant to abort kernels. Drought is the most common cause of stress. Water deficiency will limit the amount of transpiration and photosynthesis in the plant. However, this year, excessive rainfall has also been a common theme, particularly during July and August. Saturated soils will limit the amount of oxygen available to the roots and cause nitrogen loss.

-- No. 5: Uneven Emergence

If plants do not emerge evenly, delayed plants will continually struggle for sunlight, moisture and nutrients. These late-emerging plants typically will have a smaller diameter stalk and ear with more tip back.

-- No. 6: Limited Photosynthesis

Foliar leaf diseases and cloudy days also limit photosynthesis. Disease pressure has been higher than normal this year, especially southern rust, tar spot and northern corn leaf blight. Heavy disease pressure limits the surface area of the plant that can produce photosynthesis. Similarly, conditions that reduce solar radiation -- like cloudy days or haze from Canadian wildfires -- will reduce photosynthetic activity. In response, plants will start aborting kernels because there aren't enough resources to fill all the pollinated kernels. Nutrient-deficient plants also lack the resources to support grain fill.

Need a refresher in how to measure the yield penalty for tip back?

Read "Corn Yield Matters" on how to estimate corn yields: https://www.dtnpf.com/….

Read Purdue University's release on tip back and how to assess kernel loss here: https://www.agry.purdue.edu/….

Find more agronomy blogs from Burrus Seed here: https://burrusseed.com/….

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Editor's Note: If you have been following the 2025 DTN Digital Yield Tour, you'll know that our proprietary crop models also are showing high yields for most of the key corn and soybean producing states. As with most other yield models, the DTN models use satellite imagery which concentrates on the crop health signature given by the top of the crop. That imagery cannot peer into the canopy nor into the soil. So, any plant stress on the lower leaves or root issues might not yet be taken into account. For more about how those models work, what makes them unique and some of the challenges posed by conditions this growing season, please see: https://www.dtnpf.com/….

Results for all states covered by the DTN Digital Yield Tour can be found here: https://www.dtnpf.com/….

Updated yield estimates will be shared in a DTN Ag Summit Series webinar on Aug. 19, along with fall weather and market outlooks. You can register for free here: https://events.zoom.us/….

Pamela Smith can be reached at pamela.smith@dtn.com

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