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Hybrid Maturity Considerations for Delayed Corn Planting

By Jeff Coulter, Extension Corn Agronomist

For much of Minnesota, the windows of opportunity for corn planting have been late to arrive and interrupted by weather. This article addresses several concerns about late-planted corn.

Expected yield remains high for corn planted by May 25

University of Minnesota Extension planting date studies show that highest corn yields typically occur when corn is planted by early to mid-May. However, high corn yields can still occur if planting is completed prior to Memorial Day.

In a study from 2009 to 2011 at Lamberton, Morris, and Waseca that was funded by the Minnesota Corn Growers Association, grain yield was still within 93% of the maximum if planting was completed by May 25. In another study from 1988 to 2003 at Lamberton, a planting date of May 25 resulted in grain yields that were 87% of the maximum. With this year's late spring, yield reductions due to delayed planting will likely be similar or less than those observed in the study conducted from 2009 to 2011.

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Avoid planting when soils are too wet

Although it is important to finish corn planting as soon as possible now, it is equally important to avoid planting when soils are too wet. Sidewall smearing can occur when double-disc openers cut through wet soil, resulting in compacted soil around the seed that is difficult for nodal roots to penetrate. Seed furrows can also open up after fine-textured soil dries following wet conditions at planting, resulting in poor seed-to-soil contact and poor stand establishment.

Stick with planned hybrids a little longer

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Relative Maturity and Grain Moisture.jpg
In order to maximize economic return, a general guideline for growers in Minnesota is to stick with the planned seed choices until May 25. This is supported by a University of Minnesota Extension study conducted at Lamberton and Waseca in 2010 to 2012 that was funded by the Minnesota Corn Growers Association and is shown in the figures below. In this study, highest grain yield occurred with mid- to full-season hybrids (99- and 104-day relative maturity), even when the average planting date was as late as May 24. However, grain moisture at harvest was 2.3 percentage points higher with the 104-day hybrid than the 99-day hybrid with the late planting date (May 24).

When corn planting occurs between May 25 and May 31, it is wise to use hybrids that are 5 to 7 relative maturity units earlier than full season for the region. This reduces the risk of the corn being frozen prior to physiological maturity in early autumn.

Planting grain corn after May 31 carries high risk in Minnesota. If corn must be planted after May 31 in Minnesota, growers can reduce their risk by planting hybrids that are about 15 or more relative maturity units earlier than full-season hybrids.

At June 5 or later, most growers in Minnesota that still need to plant should consider planting a crop other than grain corn if feasible. However, the decision of what to plant is also influenced by factors such as fertilizer applied and seed availability. These factors will need to be evaluated on a field by field basis.

Additional information

Corn production:
Late planting:
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