Corn Delay Checklist

Considerations for Late-Planted Corn

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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Planting into wet soils or before major rain events can give corn seedlings a rough start, as they can immediately face compacted and crusted soils. (DTN photo by Pamela Smith)

ROCKVILLE, Md. (DTN) -- Delayed corn planting throws a lot of tough choices into a farmer's lap, with very little time to make the right call.

Here we review the research on late-planting decisions, such as hybrid maturity changes and the risks of "mudding in" corn, with links to helpful resources on each.


Decades of research have convinced Purdue University corn specialist Bob Nielsen and many Midwest agronomists that changing to a shorter season corn hybrid is not usually necessary before late May -- May 25 is the date often mentioned.

If you do near or pass this date and decide to move to a different maturity group, try to stay within the normal range for your region, urged Ohio State University's Extension corn specialist Peter Thomison. For example, an Ohio grower should probably not dip much lower than 102-day corn hybrids, since commonly used hybrids for the state range from 102- to 114-day maturities. Going too far beyond your region's norm will strain seed availability and run the risk of getting seed without the right genetic tolerance for local disease, insects and environmental factors, which can substantially impact yield, Thomison noted.

Together with USDA, university agronomists developed a tool to help growers find hybrids that will likely safely mature before typical freeze dates for their region.

Click this link to see the tool:…

However, the tool does not account for an important phenomenon -- corn hybrids planted after May 1 require fewer growing degree days (GDDs) to mature than early-planted fields.

"Based on research we conducted some years ago...hybrids planted later than about May 1 mature approximately 6.8 fewer GDDs for every day of delay beyond May 1, through at least the second week of June," Nielsen wrote in a recent article for Purdue.

For more details on when and how to switch corn hybrid maturities, see Nielsen's article here:…


Planting corn into overly wet soils, known as "mudding it in," comes with a host of risks to consider. Sidewall compaction is common when heavy equipment moves over soggy soils, which can restrict roots later in the season, particularly if the weather turns hot and dry, Thomison noted. That will limit the plants' ability to take in water and nutrients and tolerate late-season stress.

See a Michigan State article on avoiding sidewall compaction here:…

Planting corn before significant rainfall events are forecasted also has its downsides. After heavy rainfalls, soils can crust over as they dry and entomb corn seedlings below the surface. "If a plant starts leafing out underground, that's a fatal condition," Thomison said.

Ponding and overly saturated soils can also starve young corn seedlings of the oxygen they need.

A University of Nebraska article explains the potential consequences of flooded corn, from poor root systems, denitrification, water-borne fungal diseases, green snap, and root lodging:…

Planting into marginal soil conditions will inevitably produce some emergence and stand problems -- and bring the challenge of replanting decisions along with it. Anticipating that, University of Nebraska crop specialists have gathered the most important replant decision-making tools here:…


If corn planting slips into June, many growers will have to decide if they should take the prevented planting option or switch to soybeans, which can be planted later into the summer. The decision is an especially fraught one this spring, thanks to an unpredictable soybean market.

For some agronomic considerations on this choice, see this article from Nielsen:…

Growers' fertilizer and herbicide decisions on a field will effect a grower's ability to switch crops. Many residual herbicides, in particular, have plant back restrictions that push soybean planting too deep into the summer to be feasible:…

Corn growers will likely want to carefully calculate their potential prevented planting coverage at USDA's Risk Management website:…, and compare it to potential income from a soybean field planted in June:…

See DTN's story on the decision to take prevented planting here:…


Remember that late-planted corn isn't always a bad thing, particularly if the weather cooperates later in the summer.

Corn planted in late May or early June can take advantage of warmer soils to emerge quickly, yielding healthier and more uniform stands than some April-planted fields, Thomison pointed out.

"A crop planted later typically pops out of ground and can outgrow diseases like Pythium and Fusarium," he noted.

Finally, remember that late planting is only one of the yield-limiting factors facing a corn field, and it's not always the biggest one.

Insects, disease, drought, floods -- or the lack thereof -- are often bigger determiners of yield, Nielsen stressed in a recent Purdue article.

"...Delayed planting of corn in an otherwise high yielding year may still be higher yielding than a crop planted on the optimum planting date in an otherwise lower yielding year," he wrote.

See the full article here:…

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Emily Unglesbee