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Weather Delays Corn Planting but High Yield Potential Exists

By Jeff Coulter, Extension Corn Specialist

Expected yield is high for corn planted by mid-May

Today's USDA crop report indicates that only 4% of Minnesota's corn acres have been planted, with the majority coming from southwestern Minnesota. In comparison, the 5-year average (2009-2013) is 30%. With the recent and expected rainfall, many growers may not be able to resume field work until at least this weekend or early next week. This has led to questions about corn yield potential when planting is delayed.

University of Minnesota planting date studies show that highest corn yield typically occurs when planting is completed by mid-May. In a study from 2009 to 2011 at Lamberton, Morris, and Waseca, MN that was funded by the Minnesota Corn Growers Association, average grain yield was within 98% of the maximum if planting was completed by May 15. In another study from 1988 to 2003 at Lamberton, MN, a planting date of May 15 resulted in grain yields that averaged 95% of the maximum. These same studies found that corn yield averaged 92 to 95% of the maximum when planting occurred by May 20.

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Yield advantages associated with early planting typically are greatest when there is warm weather and rapid growing degree day accumulation between the first and second planting date windows. Given the limited growing degree days that have accumulated since April 21 and are expected over the next few days, corn emergence date is not likely to differ greatly between planting dates of April 21 and May 5 in this year. This will likely result in in similar grain yields between these planting dates, assuming that stand establishment with the early planting date is adequate.

Avoid tillage and planting when soils are too wet

Although timely planting is important, it is equally important to avoid tillage and planting when soils are too wet. In general, a field is fit for seedbed preparation when soil in the depth of tillage crumbles when pressed together rather than forming a ball.
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Sidewall smearing can occur when double-disc openers cut through wet fine-textured soil, resulting in compacted soil around the seed that is difficult for nodal roots to penetrate. In addition, seed furrows can 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 for now

In order to maximize economic return, a general guideline for growers in Minnesota is to stick with the planned seed choices until around May 21-25. This is supported by a University of Minnesota 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- and 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).
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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 froze in early autumn prior to reaching maturity.

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.

Expected yield for planted corn is high

Most of the planted corn in Minnesota has been planted in fields with soil conditions that were suitable for preplant tillage and planting. However, cool and wet weather since the middle of last week is creating less than ideal conditions for germination and emergence. Seed quality in most planted fields should be fine, but it is a good idea to scout planted fields for seed quality once it dries out. This is especially true for low-lying poorly-drained portions of fields that have received considerable rainfall since planting. Seed quality can be checked by digging up several planted seeds from different areas in a field and checking for seed firmness and discoloration. Seeds that are soft or discolored may have problems with emergence.

Additional information on corn production

From the University of Minnesota:

From across the U.S. Corn Belt (Purdue University):
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