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As corn reaches the milk, dough, and dent stages of development, growers turn their attention to an all-important question: How much yield can they expect from their crop? Using the popular yield component method and a series of simple calculations for estimating corn yield, growers can form some baseline expectations for this year’s harvest. Keep reading to learn how, or learn how corn yield expectations for 2024 are impacting markets.
Despite the economic uncertainties of farming life—the ups and downs that most of us are all too familiar with—average corn yields in the United States have been on a strong upward trend for decades, thanks to continually improving genetics and advancements in farm production techniques. Consider that in 1950, the average corn yield in the U.S. was around 38 bushels per acre.1 That figure had risen to 137 bushels per acre by 2000,2 and in 2023 corn yields averaged a record 177.3 bushels per acre—more than four times the 1950 average.3
📸: @John Rehg via Canva/Featuring an image of a full bin at harvest
While it’s great that trends are moving in the right direction, we don’t live our lives on a trend line but in our day-to-day, season-to-season work and with the ever-present variability and uncertainty of one crop year to the next.
Establishing a reasonably accurate estimate of our upcoming yield is one important way of mitigating some of that uncertainty. Knowledge is power, and the more information we have about what we might expect from our farms—from these crops, this year, in these fields—the more effectively we’re able to manage our operations and make important decisions about things like storage, marketing, budgeting, insurance, and more.
Estimating corn yield involves performing a few simple calculations based on a small sample of your crop. Many growers prefer the yield component method for estimating corn yield before harvest.
If your crops vary across fields in hybrid selection or planting date, just repeat the method in your various fields and combine the results. The more portions of fields you have time to sample, the more accurate your final estimate will be. The process might take twenty minutes at each spot you choose to sample, or even less if you can draft a helper.
Since this method relies on counting a representative sample of ears and kernels, you’ll need to wait until the kernels are established and plants have arrived at the milk stage (R3).
The components considered in the yield component method are:
● Ears per acre
● Kernel rows per ear
● Kernels per row
● Kernel weight (usually tallied in terms of kernels per bushel)
Mark off 1/1000 of an acre as a sample section. This is simpler than it might sound. If your corn is planted in 30-inch rows, just measure off an interior section of one row that’s 17 feet, 5 inches long. (You might want to cut a rope to that length for speed and ease of use when checking multiple sections of your fields.) This line of plants is your 1/1000 acre and your basis for estimation.
If your row spacing is not 30 inches, the length of your sample line will vary. For 22-inch rows, measure off 23 feet, 9 inches. For 20-inch rows, use 26 feet, 2 inches.
📸: @Groveb via canva/ Featuring an example of sample sections for estimating yield
To arrive at a sample length in fields with any other spacing, divide 43.45 by your row spacing as measured in feet. The result will be your sample length. For example, in a field with 36-inch rows, , the sample length should be approximately 14 feet, 6 inches:
43.45 ÷ 3 (row spacing in feet) = 14.48 feet (approximately 14 feet, 6 inches)
Count the number of harvestable ears in your sample section of corn. Don’t consider ears that are obviously under-developed or that will likely be missed by the combine.
Let’s construct an example and assume we find 27 harvestable ears in our sample section.
To establish an average kernel count, pull the husks back on 3-6 ears from your sample section. These will be our test ears. It’s best to select test ears on a preset random basis in "order" to avoid selection bias: for example, choose an ear (if harvestable) from every fifth plant or every sixth plant.
On the selected test ears:
● Count the number of kernel rows around the circumference of each ear and determine an average. In our example, let’s say the average number of rows in our test ears is 20 kernel rows per ear. Corn will always have an even number of rows, with 16 or 18 being the most common.
● Next, count the estimated number of kernels in the average row. Don’t include kernels at the butt or tip end of the ear but stick with those in the main section where there is a full number of rows around the cob. For our example, we will assume our test ears have an average of 25 kernels per row.
Multiply average rows per ear by the average number of kernels per row.
📸: @Sandramati, @Ende Sand and @markes51 via Canva/Featuring an example of how to calculate the kernels-per-ear total
Using our example numbers:
20 kernel rows × 25 kernels per row = 500 kernels per ear
We’re nearly ready to calculate our per-acre yield estimate. First multiply the number of harvestable ears in our 1/1000-acre sample section (from Step 2) by kernels per ear (from Step 4) to get the number of kernels in our sample section.
📸: @Lilokai via canva/Featuring an example of how to calculate per-acre corn yield
So, in our example:
27 ears per sample section × 500 kernels per ear = 13,500 kernels per sample section
Finally, we'll divide our kernels-per-sample-section by 90. Why 90? Because it's 1/1000 of 90,000, which is a standard count of kernels per bushel of corn.
13,500 ÷ 90 = 150 bushels per acre
It’s important to know that 90,000 kernels per bushel represents an average standard, reflecting average grain fill and average growing conditions. Depending on seed variety, size of kernels, crop conditions and other variables, the number of kernels per bushel can fluctuate considerably.
For instance, in a year of stressed corn and smaller kernels, a bushel might comprise 100,000 kernels or more. An excellent growing season, on the other hand, may result in better grain fill and larger kernels, which translate to a lower kernels/bushel count – perhaps 75,000 to 80,000.
You can take those variables into account and instead of using 90 in the above formula, plug in the appropriate figure: 100 for 100,000 average kernels per bushel, 75 for 75,000, etc. The yield component method of estimating corn yield is considered relatively accurate within plus or minus 20 bushels per acre.
Keep in mind that while estimates can give you a ballpark feel for what to expect at harvest time, they are not guarantees. In other words, you can’t rely on them as absolute indicators of your final results. However, you can improve the accuracy of your estimates by following the steps outlined above in different areas of your fields and averaging the results to get a holistic yield estimate.
Experts are available to help you maximize your corn yield. Reach out to a nearby extension office agent or a professional like your regional BASF representative to make an informed choice.
Discover how to optimize your corn crop this season:
● Planning for Plant Health in Corn
● Growing Corn: How and When to Plant Corn, Step by Step
● Corn Growth Stages: From Planting to Harvest
For an interesting take on how yield-estimate accuracy can change over the course of a growing season, see “Fall Yield Estimates and Errors” at Grow Smart Live.
Visit the Grow Smart® Live homepage to read about topics that are important to farmers in your area and to experiment with Grow Smart® Live Advantage, an online tool that lets you compare crop protection products and helps you get the best yield out of your acres.
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