The U.S. average corn yield was record large in 1985, 1986 and 1987, and established new highs five times in the succeeding 26 years. Similarly, the U.S. average soybean yield was record large in 1985 and established new highs eight times in the succeeding 26 years.
The most recent record yield was in 2009 for both crops. Average yields were below trend value in each of the past four years.
Expectations for the U.S. average corn and soybean yields this year have increased in recent weeks. Corn planting got off to a slow start, much like last year. Even though progress accelerated in May, more than the average percentage of the crop was planted after the third week of May. Based on the USDA's weekly Crop Progress report, an estimated 23% of the corn acreage in the 18 major corn producing states was planted after May 20, compared to the 1986 through 2013 average of 15%. More than the average portion of the corn acreage was planted late in five of the past seven years.
Most of the late planting this year occurred in northern and far eastern corn producing states. Yield potential is reduced for corn planted after the second or third weeks of May, all other conditions equal. However, weather conditions over the past month have been generally favorable for corn emergence and development, resulting in high yield expectations in spite of more than the usual amount of late planting.
USDA acknowledged these conditions in the June 11 World Ag Supply & Demand Estimates (WASDE) report as the reason for keeping the 2014 yield projection at a record 165.3 bushels per acre.
USDA's weekly ratings of corn conditions have also supported high yield expectations. As of June 8, 75% of the crop in the 18 major corn producing states was rated in either good or excellent condition. In the previous 28 years (excluding 1995 when ratings were not yet available due to extremely late planting) an average of 66% of the crop was rated in good or excellent condition at the end of the corresponding week. The portion of the crop rated in good or excellent condition was higher than this year in only five previous years.
Crop condition ratings tend to decline as the growing season progresses and early season ratings are not a good indicator of either final ratings or the U.S. average yield. Still, the current high ratings, along with a mostly favorable weather outlook, are keeping yield expectations high. The major concerns in the near term center on deteriorating conditions in areas that have received excessive rainfall in recent weeks. The effect of flooding and ponding may begin to be revealed in the crop condition ratings to be released today. Those concerns are legitimate, but are likely outweighed by the beneficial impact of favorable weather in most areas.