Update from the Field: Kernel of Truth
Posted on September 09, 2020
There are two common questions being asked this time of year: 1) how is the corn crop progressing, and 2) what are the yield estimates for the 2020 corn crop? Scouting the corn field at 55 miles per hour will not tell you much; the only way to get an accurate sense of the 2020 crop is to stop and walk into the field.
The first thing to do when walking into a field of corn is to push on the stalks. Giving the corn stalks a little shove will give insight on stalk strength to determine if disease or insects have weakened the corn plant. If the stalk is weak, the field will need to be put at the top of the priority list for harvest. Weakened corn stalks will be the first to fall over once the corn matures.
Next, walk past the “end rows” and into the main part of the field, or about 60 feet if walking in from the side of the field. This ensures yield estimations are being made past any compaction issues related to turning equipment around. If the corn rows are 30 inches apart, which is standard, mark off 17 feet and 5 inches. This represents 1/1000 of an acre, which makes calculations simple and easy. If the corn rows are not 30 inches, use the table below to determine the length of row depending on row width, Figure 1. Count the corn plants that will bear an ear between your marks: this will be the population in 1/1000 of an acre. Write that number down for later use. Shuck back the 5th, 15th, and 25th ears in the row. Doing this will ensure the randomness of the sample. Write down the average number of rows around each of the three ears. As an example, Figure 2 shows 18 rows. Write down the average number of kernels per row on each of the three ears. As an example, Figure 3 shows 36 kernels per row. Stop counting a few kernels from the tip. Insert these numbers into the equation below, Figure 4, to estimate corn yield. You will need to repeat this process every 10 acres to get an accurate yield estimate of the field.
Figure 1: The table above, adapted from Iowa State University, can be used to determine the length of row equivalent to 1/1000th of an acre, depending on row width.
Figure 2: This picture shows the number of rows around an ear of corn to be 18. All ears will have an even number of rows around the cob. This picture was taken at the Walton Farm Center crop plot in 2020.
Figure 3: This picture shows the number of kernels in a row to be 30. Do not count all the way to the tip or the base when counting kernels in the row. This picture was taken at the Walton Farm Center crop plot in 2020.
Figure 4: Equation for estimating corn yield.
The kernel weight number is the number of kernels per bushel. Depending on weather, soil, and hybrid genetics the kernel weight can vary from 65,000 kernels/bu for heavy corn to 100,000 kernels/bu for light corn. I like to use 90,000 (or 90 because we are only looking at 1/1000 of an acre) for the numerical factor. This will give a lower estimate, but it’s always better to be pleasantly surprised than disappointed.
In conclusion, get out and scout fields right now! Planning for a potential crisis or success will prepare you for harvest.
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Dave Dyson is a regional agronomist for The Andersons’ Farm Centers which are located throughout Ohio, Michigan, and Indiana. He is an Indiana native and grew up on a dairy farm in Miami County. A graduate of Purdue University with a degree in Crop & Soil Science, Dave has a deep knowledge of various agronomic topics and is committed to helping growers improve their crops. If you have any questions, Dave can be reached at david_dyson@andersonsinc.com.
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