ST. PAUL -- Corn planting still is weeks away in much of Minnesota because of wet conditions and cool soils.
Long-term data from the University of Minnesota indicate that the optimum planting date for corn in Minnesota is during the last week of April and the first week of May. The average yield reduction is about a half-bushel per acre each day that planting is delayed from April 28 until May 21. In addition to higher yield, earlier planting can result in earlier maturity, allowing more time for drying of grain in the field before harvest and fall tillage.
While timely planting is important, the advantages of an earlier planting date can be lost if tillage and planting operations occur when the soil is too wet. For example, sidewall smearing can occur as planter disk openers cut through wet soil, resulting in compacted soil around the seed that is difficult for seedling roots to penetrate.
Seed furrows also can open up after the soil dries when it is too wet at planting. In addition, soil compaction from heavy machinery on wet soil can reduce yield this year and in the future. Planting into cool and wet soils also increases the potential for seedling diseases.
Planting research
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Recent research by University of Minnesota Extension Service corn agronomist Jeff Coulter reinforces early planting as a recommended practice, but there was little yield loss when planting was delayed until May.
Coulter's research (2008 to 2010 in Lamberton and Waseca, Minn.) shows that a late April planting (average date of April 28) produced 208 bushels per acre, while mid May (average date of May 12) produced 204 bushels per acre. A late May planting (average date of May 26) produced 177 bushels per acre when a 102-day hybrid corn was planted at 34,000 plants per acre.
Keep in mind that while higher corn yield is associated with earlier planting, the planting date is just one of many factors that determine yield. Avoid "mudding the seed in" just to get the crop planted early. Instead, wait for proper soil conditions and perform tillage operations only when necessary.
To reduce the prevalence of corn seedling diseases, use high-quality, fungicide-treated seed, and plant when soil temperatures are more than 50 degrees and soil moisture is adequate but not excessive. Corn seed treatments usually are most effective for only two to three weeks after planting.
Editor's Note: Nicolai is a crops educator with the University of Minnesota Extension Service in St. Paul.
