Calculating Corn Yield Estimates
Yield estimates can be made using the yield component method. This method uses a combination of known and projected yield components of corn to calculate an estimate of the potential yield. It is "potential" yield because one of the critical yield components, kernel size, will not be known until physiological maturity. Before then, one can use only an estimate of predicted yield based on what you think the grain filling period might be like (e.g. favorable, average, or poor).
Estimating potential corn yield using yield components is accomplished using the following elements:
Ears per acre: This is determined by counting the number of ears in a known area.
With 30-inch rows, 17.4 feet of row = 1,000 of an acre. This is probably the minimum area that should be used. The number of ears in 17.4 feet of row x 1,000 = the number of ears per acre. Counting a longer length of row is fine, just be sure to convert it to the correct portion of an acre when determining the number of ears per acre.
Make ear counts in 10 to 15 representative parts of the field or management zone to get a good average estimate. The more ear counts you make (assuming they accurately represent the field or zone of interest), the more confidence you have in your yield estimate.
Kernels per ear: This is determined by counting the number of ear rows and number of kernels in each row. Multiply those two items to arrive at kernels per ear (number of rows x kernels per row).
Do not count aborted kernels or the kernels on the butt of the ear; count only kernels that are in complete rings around the ear. Do this for every 5th or 6th plant in each of your ear count areas. Avoid odd, non-representative ears.
Kernels per acre = Ears per acre x kernels per ear
Kernels per bushel: This will have to be estimated until the plants reach physiological maturity.
Common values range from 75,000 to 80,000 for excellent, 85,000 to 90,000 for average, and 95,000 to 105,000 for poor grain filling conditions. The best you can do at this point is estimate a range of potential yields depending on expectations for the rest of the season.
Ears per acre = average of 22.5 ears in 17.4 ft of row (1/1000 acre).
22.5 x 1,000 = 22,500 ears per acre
Kernels per ear = average of 14 rows x 27 kernels per row.
14 x 27 = 378 kernels per ear
Kernels per bushel = estimating 105,000 kernels per bushel, based on poor growing conditions.
Calculation: Ears per acre x Kernels per ear = Bushels per acre
Kernels per bushel
22,500 ears per acre x 378 kernels per ear = about 81 bushels per acre
105,000 kernels per bushel