Weather conditions are delaying the onset of corn planting, but wide fluctuations in corn planting progress are not uncommon in Minnesota. By the end of April, about 50 percent or more of Minnesota’s corn acres were planted in 2009, 2010 and 2012, compared to less than 5 percent in 2008 and 2011.
While most growers prefer to get their crops off to an early start, early planting is not a requirement for high yields. In 2008 and 2011, when it was mid-May before half of Minnesota’s corn acres were planted, state-average grain yields ranked third and fifth among Corn Belt states, respectively.
This is supported by University of Minnesota Extension corn planting date studies conducted at the University’s Research and Outreach Centers. In a study from 1988 to 2003 at Lamberton, planting dates ranging from April 21 to May 6 produced grain yields within 1 percent of the maximum. In another study from 2009 to 2011 at Lamberton, Morris, and Waseca that was funded by the Minnesota Corn Growers Association, grain yield was within 1 percent of the maximum when planting occurred between April 25 and May 10. In both studies, rapid decline in corn yield did not occur until planting was delayed beyond mid-May.
Corn requires soil temperatures of 50 degrees Fahrenheit or higher for germination. However, once the last week of April is reached, corn planting should generally occur as soon as soils are dry enough, regardless of soil temperature. If corn is planted into soils that are too wet, the advantages of an earlier planting date can be negated due to soil compaction around the seed zone, which can result in poor growth of nodal roots and reduced uptake of water and nutrients.
A planting depth of 2 inches is generally optimal for most planting dates and soils, but can be deeper on coarse-textured soils to ensure that the seed is placed in moist soil. Avoid the temptation to plant corn shallow when soils are cold, as planting depths less than 1.75 inches increase the risk of poor nodal root development and root lodging later in the season.
In order to maximize economic return, a general guideline for growers in Minnesota is to stick with the planned seed choices until May 20 to 25. When planting occurs after May 20 to 25, it is wise to switch to hybrids that are 5 to 7 relative maturity units earlier than full season for the region.
For more resources on corn production from University of Minnesota Extension, visit www.extension.umn.edu/corn.