May 2, 2013
2013 U.S. Corn Yield Estimated at 155-156 bu/ac
Barring any additional extended periods of wet weather in the central Corn Belt during the month of May, it looks like the bulk of the corn crop will be planted approximately 2 weeks later than normal. Generally, corn yields start to decline if the crop is planted after May 10-15th in the central Corn Belt and the longer the planting is delayed, the greater the yield declines.
In broad terms, if the planting is delayed until May 15-20th, the yield declines 0.5 bushel per day for each day the planting is delayed. That increases to 1.0 bushel per day for each day planting is delayed from May 20-25th. It increases to 1.5 bushels day if planting is delayed until May 25-30th and 2.0 bushels per day if planting is delayed until early June. Having said that, we also must remember that there is not a hard and fast relationship between date of planting and eventual yields. Late-planted corn can do fine if the weather cooperates during the summer (2009 is a good example). Conversely, early-planted corn can be very disappointing if the summer weather does not cooperate (2012 is a perfect example).
Several months ago we were concerned about low U.S. corn yields due to inadequate soil moisture. Now that the soil moisture concerns have been largely eliminated, we are concerned about lower yields due to delayed planting. Therefore, I would now estimate the 2013 U.S. corn yield at between 155-156 bushels per acre. If there are no additional prolonged periods of wet weather during the month of May, the nationwide corn yield could potentially move higher. If wet weather during May delays planting even more than what is already anticipated, then the early corn yield estimate may decline.