Farmers with wet fields are feeling frustrated and even anxious about when they’ll be able to start planting.
Hold steady and stick with your original plan for now, advises Brent Tharp, Wyffels technical product manager.
“Even if we get into May 15, we’re still at 95% of the yield potential for the yield (in Iowa and Illinois),” Tharp says. “Even if we get out to May 20, we’re still at 92% of the yield potential for that particular year.”
Bob Nielsen, Purdue University Extension corn specialist, writes that the estimated yield loss per day with delayed planting varies from only about 0.3% per day early in May to about 1% per day by the end of May.
“Relative grain yield potential goes down with delayed planting because of a number of factors including a shorter growing season, greater insect & disease pressure, and higher risk of hot, dry conditions during pollination,” he says. (See The Planting Date Conundrum at https://bit.ly/3vLi2fx.)
Corn Yields Are Increasing
Last week, given the continued rain, Tharp decided to take a deeper dive and evaluate the correlation between planting date and final corn yield results in both states.
“I wanted to see if there a relationship to planting date, whether the yield is above or below the trendline,” he says.
USDA data shows that trendline corn yields in the U.S. continue to increase. Tharp says the main driver for is genetic improvements in plant breeding.
“Even so, when you observe trendline yields, you will see there are years above the trendline and other years below the trendline,” he says.
The Relationship Between Planting Date And Yield
As he looked at USDA statistics, he honed-in on the 50% corn-planted date – when that occurred during a 25-year period from 1997 to 2021. He then plotted that information against the final corn yield for each state and whether it was above or below trendline.
What he determined is there is no strong correlation between the corn planting date and final yield. (See Iowa and Illinois charts, left.)
“Planting date is important – I don’t want to underestimate it. But it isn’t the driver for where we finish up for final yield,” he says.
Instead, in-season events often affect yield more than planting date, Tharp notes. Two events he references are the 2020 derecho that hit parts of Iowa and Illinois and the 2012 drought, which took a huge toll on most of that year’s corn crop in the Midwest.
In fact, he found that in some years when farmers have planted late yield results were above trendline. Corn yields in 2018 and 2019 are two examples.
As the rains continue this first week of May, Tharp advises farmers to be patient. He offers two additional recommendations:
1. Try to plant when the conditions are finally good for corn. It’s better to plant into ideal conditions in mid-May than to muddy the crop in now.
“It’s good to have those nodal roots established and have good root growth. Whereas, if we mud the crop in, we’ll pay the consequences later if we have a dry, stressful end of the season,” Tharp says.
2. Don’t switch out your full-season hybrids yet. Tharp says stick to your original plan until the last week of May, because corn plants are able to adapt to the environment in which they’re planted.
“Let’s hope you don’t have to make that decision, and Mother Nature gives us a window here really soon to plant,” he says.
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