According to USDA figures, September corn production forecasts are down 28 million bushels from August to 9.24 billion bushels. With a chance for continued declines in future forecasts, many producers are interested in predicting now, how their yields will weigh in. Dan Johnson, agronomy services manager for Mycogen Seeds, says a walk through fields will enable growers to make very accurate grain yield estimates.

He suggests following a formula that uses a numerical constant for kernel weight.

“The yield estimation should only be used to calculate relative grain yield because weight per kernel will vary depending on the hybrid and environmental conditions,” Johnson says. “Actual final yield may differ.”

The following is a simple way to calculate relative grain yields:

1. Count the number of harvestable ears per 1/1000 of an acre. For example, if row spacing is 30”, then 17’ 5” of a row equals approximately 1/1000 of an acre. Those ears should be used for the count.
2. Count the number of kernel rows per ear on every fifth ear. Calculate the average.
3. Count the number of kernels per row on each of the ears, but do not count kernels on the butt or tip that are less than half size. Calculate the average.
4. To generate the number of kernels per 1/1000 of an acre, multiply the number of ears in the row by the average number of kernels.
5. Under most circumstances, 90,000 kernels are equal to approximately one bushel. To get an estimate of the number of bushels per acre of your crop, divide the number of kernels per 1/1000 of an acre by 90.

Johnson reminds growers that samples from one area of a field may not represent the field, as a whole, better than samples from other areas.

“Pick the three ears you will count kernels on beforehand and stick to it,” he says. “Also, do the estimate in several places in the field for more accurate results.”

If there’s reason to think that kernels will be larger than average, then Johnson says to divide (in step 5) by a number less than 90 – for example, 80 or 85. However, divide by 100 or more to adjust for smaller kernels.

“The principle advantage to this calculation method is that it can be used as early as the milk stage of kernel development,” he says. “But, I remind growers that the number of kernels will vary by hybrid and environment, and to use this method only as an estimate of relative grain yield.”

Mycogen Seeds is a wholly owned subsidiary of The Dow Chemical Company and is an affiliate of Dow AgroSciences LLC. Mycogen Seeds is the leader in Silage-Specific™ corn, the largest sunflower seed producer, and a leading producer of seed corn, alfalfa, soybeans and sorghum. For more information on Mycogen Seeds, go to www.mycogen.com on the Internet.