With the current heat wave and continuing lack of rain, non-irrigated corn is declining in quality daily. Where corn must be harvested for grain, getting some idea of yield potential can help us make decisions about the crop- whether to revisit the amounts contracted or call the crop insurance adjustor.  If you checked yield potential a week or two ago, you may want to check again. Some kernels that looked promising may not have made the cut. Corn yield estimates can be made as early as the R3 (roasting ear) stage although in a dry year please note that estimates can vary widely from the end result due to late season kernel loss.  The following is a basic formula for estimating corn yield with conversions for the amount of stress occurring during the season.

1. Ear Count:  Estimate harvestable ears in 1/1000th of an acre by counting plants with viable ears in a specific row length (30 in rows is 17.4 ft; 15 in rows is 34.8 ft; 36 in rows is 14.5 ft; 38 in rows is 13.75 ft).  Do this in 4 or 5 locations representative of the field to obtain an average.  In a drought situation we may have more barren stalks or short plants with delayed ears that won’t develop and this step helps account for those in the field.

2. Ear Size: Randomly pull 3 to 5 ears per location and count rows of kernels around the cob and kernel numbers long and get an average number of kernels per ear.  To count ear length, count only full rings of kernels and be careful to not over count those tip end kernels which are least likely to fill in a drought year.  I would suggest starting 1 row up from the bottom and stop when kernels start to look noticeably smaller in size or are still at blister stage as those may not fill completely and will most certainly be lighter weight (Example:  average 14 rows X 24 kernels= 364 ear size).  This year ears may be tipped back 25 to 33% or more depending on field conditions.

3. Correct for Stress:  (Ear Count) X (Average Ear Size)/Stress Factor= Bu/A Estimate

(Example:  (30 ears) X (364 ear size) / 95= 115 bu/A