By Jeff Coulter, University of Minnesota Extension
Weather conditions in Minnesota are leading to a slower start for the 2011 corn planting season. Last year, 13 percent of the corn in Minnesota was planted by April 18 and 63 percent by April 25.
In order to maximize yield and economic return, a general guideline for growers in Minnesota is to stick with the planned seed choices until May 25. When planting occurs between May 25 and May 31, it is wise to switch to hybrids that are 5 to 7 relative maturity units earlier than full season for the region.
In Minnesota, planting corn in June is risky due to the high potential for a killing freeze in the fall before the crop has reached maturity. However, if corn is planted in the first week of June, this risk can be reduced by planting hybrids that are at least 8 to 15 relative maturity units earlier than full season.
Long-term planting-date trials at the University of Minnesota Southwest Research and Outreach Center from 1998 to 2003 found that corn yield was maximized on average when planting occurred between April 21 and May 6, although optimum planting dates for individual years varied with weather and soil conditions.
University of Minnesota Extension research over the past three years in southwestern and south-central Minnesota, funded by the Minnesota Corn Growers Association, showed that corn yield was reduced by an average of 3 percent when planting was delayed from late April to mid-May and by 15 percent when planting was delayed until late May. However, the date of crop maturity in the fall was reduced by just 4 to 5 days for each two week delay in planting beyond late April.
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 early planting date can be negated due to soil compaction around the seed zone, which can result in poor nodal root growth and subsequent root lodging.
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. Planting depths of 1.75 to 2 inches are generally optimal for most planting dates and soils, but can be deeper on lighter soils to ensure that the seed is placed in moist soil.
For more educational resources on corn production in Minnesota, visit University of Minnesota Extension’s corn website at www.extension.umn.edu/corn
Jeff Coulter is a corn agronomist with University of Minnesota Extension.