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CropTalk: Yield Components of Corn

October 2022

Published on Monday, October 3, 2022

Yield of corn, measured in bushels per acre, is something that farmers strive to maximize each year. And while some components are set based on the genetics of the hybrids planted and environmental conditions (weather, soil type, water holding capacity, etc.), there are numerous management practices that can positively influence the yield of corn.

When evaluating the components that contribute to corn yield; we look at three key areas: ears per acre, kernels per ear, and the weight of kernels. Each of these components is determined at very different times throughout the growing season, and different fertility and management factors will play into maximizing each of these factors.



Ears per acre is the first yield component that we focus on in the growing season. When influencing ears per acre, we want to look at management practices that occur from planting to about the V3 growth stage time frame. During this period, the goal is to have even emergence and supply the young seedlings with an environment that is conducive to earlyseason vigor and stand establishment.

Planting is the best time to implement practices to ensure even emergence. As simple as it may be, maintaining a consistent planting depth of two inches will not only help with more uniform emergence but also the final ear count per acre. If your planting depth is shallowed up to the one-inch range, the corn plants will have issues with nodal root establishment, causing a season-long negative effect. Another way to positively influence ears per acre and drive yield is to evaluate your closing wheel setup. One of our PFR Proven™ success strategies for corn is the use of notched/spiked closing wheels. Over the past three years, our PFR testing has shown positive yield results using and aftermarket closing wheels vs. two solid rubbers. This simple change can contribute vastly to early-season stand establishment and ultimately lead to increased yield.




The next yield component that must be focused on as the season progresses is kernel number. This yield component will occur at two very distinct moments in the plant’s life depending if the focus is on kernel rows around (girth) or kernels per row (length). Around the V5 growth stage, the corn plant will begin to determine the kernel rows around. This process is typically complete by the V8 growth stage but can vary based on genetics.

Although there are hybrids that we can manage to gain an extra two to four kernel rows around, this yield component is highly dependent on genetics. It must be noted that there are several instances where a decrease in kernel rows around has been observed, primarily due to the application of off-label herbicides. The V5 to V8 time frame is a very sensitive time in the plant’s development, and it is very important to properly stage the plant and follow all herbicide application labels to avoid causing injury to the developing ear.

The other critical time when influencing kernel number on the ear is just after the girth is determined around the V8 growth stage. It can continue to be adjusted all the way until approximately one week before pollination (V15 to V20 growth stage). This period is when the developing ear will determine its potential length. In most years, the ear will develop between 1,100 to 1,200 ovules that could potentially become kernels, but by the time pollination occurs and environmental stress and genetic influence take place, the corn ear will typically end up with around 550 to 700 viable kernels contributing to yield.

With that being said, there are quite a few management practices that we can implement to help retain potential kernels prior to pollination. Nutrient uptake of three key nutrients — nitrogen (N), potassium (K), and sulfur (S) — play a large role in the development of the ear when determining kernels per row. As you can see from the uptake charts, the corn plant starts the rapid uptake of each of these nutrients around the V6 to V9 growth stages.

Not having adequate availability of these nutrients in a form that is available for plant use can lead to stress on the plant and reduction of ear length. A key management practice that has become PFR Proven is splitting N applications, with most of the N being sidedressed at the V3 growth stage. This allows for applications at a time that will be safe for the plant and allows the N to be available when the rapid uptake begins.

This stage is also a very efficient time to address the S needs of the plant. By adding ammonium thiosulfate (ATS) to your sidedress applications, you can adequately supply the plants with a plant usable form of sulfate S. This should be one at a rate of 0.1 lb. of S per each bushel of corn yield targeted. Remember, under growing conditions with ample moisture and temperatures to promote mineralization, our soils will supply approximately 3 to 5 lb. of sulfur per % OM.

The final nutrient often overlooked at this time is K. A lack of K available for uptake can cause serious yield reductions by decreasing the ear’s size and nutrient availability and movement within the plant. Potassium activates many plant functions such as photosynthesis, nutrient and water movement in the plant, cell wall formation, and stomatal control (water use efficiency). Potassium also helps with disease mitigation and nitrogen assimilation into the plant, basically saying that if we are short available K, we will have trouble having sufficient N levels in the plant. Because most of the K applied to crops is done before to the growing season, we often overlook this nutrient.

In-season applications are difficult with foliar applications and are often costly to apply at useful rates. One practice that is becoming more popular is the use of potassium thiosulfate (KTS) with the use of Y-DROP or sidedress applications. KTS (0-0-25-17s) can be used in place of ATS to apply sulfur to the plant along with available K during side dress. Farmers with lower base saturation K levels, or soils with lower K levels, may see a significant yield increases by testing this product.



The final factor in the corn yield component triangle is kernel weight. This yield factor has been responsible for the consistent year-over-year increases we have seen in corn yields and is the most influential period where a change in management practices will lead to increased yield. Two management practices that have influenced kernel weight more than any other and come with one easy application timing are the use of a foliar-applied fungicide and the addition of a boron product with the application. Foliar fungicides work to reduce the incidence of fungal diseases on the leaf surface. By keeping the leaf surface free of disease, the plant will conduct photosynthesis more efficiently, allowing for a greater accumulation of starches and sugars for filling the ear.

Another key component of fungicides, specifically the strobilurin class, is the reduction and suppression of ethylene. Ethylene is a naturally occurring plant hormone that causes the plant to ripen. With fungicide applications, this process is slowed, allowing for longer grain fill periods and higher kernel weights. Beck’s PFR data shows that the highest return on investment of fungicides comes at the VT/ R1 growth stage, but if you are in an area that is consistently battling Tar Spot or Southern Rust, please consult your Beck’s field agronomist to adjust fungicide timings and programs if necessary.

I would encourage growers to look at boron applications during fungicide applications. Boron is an important nutrient for pollen longevity, tip retention, cell structure organization, sugar, and carbohydrate movement to growing tissues (i.e, kernels). This simple addition has shown some very favorable yield results and economic returns in PFR testing.

As hybrids and genetics continue to advance and change, we must keep in mind some of the basics of crop production. Taking a deep look into the yield components of corn, when they happen, and what influences each stage can be an insight into unlocking more yield potential.

As always, if you have questions, don’t hesitate to reach out to your local Beck’s representative!



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Author: Jon Skinner

Categories: CropTalk, 2022

Tags: corn, Yield

Jon Skinner

Jon Skinner

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