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Full, Deep Kernels Could Increase Corn YieldFull, Deep Kernels Could Increase Corn Yield

Crop Watch 2014: How to estimate corn yields more accurately this year.

Tom Bechman

August 29, 2014

3 Min Read

Corn fields that haven't suffered from reduced stands or nitrogen losses due to too much rain could be set up for big yields. Agronomists say that in areas where timely rains have continued through the grain fill period, the yields may be even bigger than anticipated.

You can get an idea of yield by counting the number of ears per one/one thousandth acre. That's 17 feet, five inches in 30-inch wide rows. Do it at several locations to get a truer picture of what a good yield estimate might be. Realize that your estimate may be only 80 to 90% accurate.


Count rings of kernels on five ears selected at random. Often it's advisable to count ears and kernels on both sides of the 17 feet, 5 inch tape to get a better yield estimate at that spot. Then count number of kernels per row on each ear and average the five together to get an average number.

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Divide by a factor that varies depending upon how many kernels it takes to make up a bushel of corn. The standard used for years was to divide by 90, based on 90,000 kernels per bushel. Many believe that with modern hybrids, that may be too high, and produce a conservative yield estimate. They suggest 80 as a better number. Then in years like this when grain fill in fields that continued receiving timely rains may be exceptional, 75 or even less may be a better factor to use. This is verified in the 2014 Purdue University Corn & Soybean Field Guide.


How much difference can the factor make? Suppose you check the field and find an average of 30,000 ears per acre, with 18 rows of kernels and 40 kernels per row. The math works out to 21,600 divided by a factor. First divide by 90, the standard for many years. Your yield estimate would be 240 bushels per acre.

Next divide by 80, a number many agronomists believe is more accurate today. Yield would be 270 bushels per acre. Finally, divide by 75 for a field that has received timely rains during grain fill. The yield estimate is 288 bushels per acre. That's a range of 48 bushels per acre depending upon which factor you choose.

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Suppose you're 20% too high in each case. New yields are 192, 216 and 230, respectively. That would still be a lot of corn!

And just in case you're chasing 300 bushels per acre, if grain fill is exceptional and the right factor is 70, reserved for excellent grain fill, you just reached 209 bushels per acre, which is still just under 250 bushels per acre if you're 20% too high.

About the Author(s)

Tom Bechman

Editor, Indiana Prairie Farm, Indiana Prairie Farmer

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