Corn Yields and Kernel Size

Posted: September 23, 2014

Illustrates how kernel size can have a big impact on yield estimates.

Late summer conditions have been relatively good for grain fill here in central PA so there is some potential for larger than average kernel size. On the other hand, some locations have been plagued with late season Northern Corn Leaf Blight and in these fields grain fill will likely be limited.

Kernel size can be a diagnostic tool that can help explain some yield differences that you might not expect. In 2012 I observed high kernel weight in fields where yields were much higher than our pre harvest estimates. Kernel sizes range from about 25 to 36 g/100 kernels or 100,000 to 70,000 kernels/bushel at 15.5% moisture.

In high yielding corn, the impact of kernel size can be striking as shown in the table below.

Table 1. Impact of kernel size on grain yield in corn.
Kernels/bushel g/100 kernels @15.5% g/100 kernels @25.0% Yield(bu/acre)*
*Assuming 16 kernel rows, 35 kernels/row and a ear count of 32000/acre
100000 25.4 28.6 179
90000 28.2 31.8 199
80000 31.8 35.8 224
70000 36.3 40.9 256

To improve your yield estimates, adjust the kernel size factor in your yield estimate. A simple tactic would be to weigh a sample of corn kernels, adjust the weight to a 15.5% basis and estimate the kernels/bushel factor. To estimate the kernels/bushel from the seed size/100 kernels in grams, use the following formula: Kernels/bushel= 2,540,000/seed size, so 2,540,000/28g = 90720 kernels/bushel.

Contact Information

Gregory W. Roth
  • Professor of Agronomy
Phone: 814-863-1018