Most farm operators in Southern Minnesota and Northern Iowa took advantage of an extended 10 to 12 day planting window from May 4 to May 15 to get nearly all of the corn planted, as well as a majority of the soybean planting completed. Growers in some areas were able to get some corn planted during a short period from April 23-25; however, most of the corn was planted on May 5 or later. Some producers have completed planting all of their corn and soybeans, while those in areas that received more rainfall in late April and early May still have some soybeans to complete.
Once the fields dried out adequately, corn and soybean planting progressed very rapidly during the period from May 4 to May 15. At the University of Minnesota Southern Research and Outreach center at Waseca, Minnesota, only .25 inches of precipitation was recorded during that time frame. Daytime high temperatures ranged from 67 to 90 degrees F during that period, and night time low temperatures were above 50 degrees F on most days. This lead to almost ideal planting conditions in most areas.
The warmer temperatures also lead to a rapid warm up in soil temperatures, which aided corn and soybean germination and rapid crop emergence. The 2 to 4 inch soil temperature at Waseca averaged nearly 60 degrees F from May 1-19, which is well above the long-term average for the first half of May, and averaged 64-70 degrees F from May 13-18. Research shows that 50 percent corn emergence will occur in 20 days at an average soil temperature of 50 degrees F, which is reduced to only 10 days at an average temperature of 60 degrees F. Some corn and soybeans planted in May this year emerged in 5 to 7 days.
Some agronomists had expressed concern that the corn that was planted from April 23-25 may have some germination and emergence issues, due to the extended cool, wet soil conditions that followed in late April and the first few days of May. However, most of the earlier planted corn appears to have germinated and survived those conditions satisfactorily, and most of these corn stands look good to excellent at this point. Many of the improved corn hybrids that are in existence today have the ability to withstand more variable early season growing conditions, as compared to corn hybrids that were available 2-3 decades ago.
Following the very warm temperatures and drier conditions from May 4-15, conditions are turned much wetter and cooler in recent days. The Outreach Center at Waseca received over 2 inches of rainfall from May 16-19, with many areas of Southern Minnesota and Northern Iowa receiving rainfall amounts of 3 inches or more during that period. In some localized areas across the region, especially in Southeast Minnesota, much higher rainfall amounts were reported from severe storms. There has been additional rainfall amounts of 1 to 2 inches or more this past weekend in many portions of the region. This has resulted in standing water in parts of some fields, which could require some replanting.
According to University of Minnesota and private seed company research, the ideal window to plant soybeans in Southern Minnesota and Northern Iowa, and still get optimum yields, extends until about May 25 or later. So, there is still some opportunity to get the 2017 soybean crop planted on a timely basis. Soybeans have a much more flexible planting window than corn for achieving desirable yields, especially in a year such as this when we have quite warm soil temperatures Most agronomists are encouraging producers to be patient with resuming field work and soybean planting, and to wait until soil conditions are conducive for good planting and seed germination.
Much of the corn in Southern Minnesota in 2017 was planted near the end or just after the typical “ideal time window”, from about April 20 to about May 7, which is usually referenced for optimal corn yields in the region. Based on long-term research, the reduction in optimum corn yield potential with planting dates from May 5-15 in Southern Minnesota is usually very minimal, and is very dependent on the growing season weather that follows. The very warm temperatures and excellent growing conditions that existed from May 4-19, which allowed for rapid germination and early growth of the corn, should help offset the slightly later planting dates in 2017. As of May 19, Waseca had accumulated 220 growing degree units (GDU’s) since May 1, which is about 24 percent above the long-term average.
Based on the May 15 USDA Crop Progress Report, 84 percent of Minnesota’s corn and 47 percent of State’s soybeans were planted by that date, which is ahead of the five-year (2012-2016) averages of 70 percent planted for corn, and 40 percent for soybeans. As of May 15, Iowa had 85 percent of the corn and 40 percent of the soybeans planted, compared to five-year averages of 75 percent for corn and 32 percent for soybeans. South Dakota had 77 percent of the corn and 29 percent of the soybeans planted as of May 15. Nationally, 71 percent of the corn and 32 percent of the soybeans were planted by May 15, which is on-pace with the five-year averages of 70 percent for corn and 32 percent for soybeans.