Planting delayed? There’s still time!

Much-needed rains have hit the Corn Belt recently, which have been welcome relief for lingering drought in some areas. However, this has also delayed corn and soybean planting during a critical window. 

The good news: It’s not time to panic yet.

Corn

One of the agronomic questions that comes up when planting is significantly delayed is whether farmers should consider switching from normal full-season maturity corn hybrids to shorter-maturity hybrids. The question is based, of course, on the perceived risk of the crop not reaching maturity before a killing fall freeze — and the yield losses that could result. 

“This is probably the first time in 15 years that we haven’t planted a kernel of corn on our own farm in April,” says Ryan Gentle, an agronomist in central Illinois for Wyffels Hybrids. “I keep reminding farmers, it’s not late yet. I don’t even start thinking about changing maturities in central Illinois until June 1. If you’re I-80 or north, more like May 25.” 

“In terms of potential yield loss, in early- to mid-May, you're only losing 0.3% potential per day,” says Dan Quinn, corn extension specialist at Purdue University. “Usually the last week of May is typically when we begin losing about 1% per day of yield potential and increases in percentage heading into early June.” 

Gentle also encourages growers to stick to their hybrid choices until the last week of May or early June. “We’ve shown with Wyffels data that for every day you go backwards in maturity, you lose about two bushel right off the bat. I'd hate to have a guy go back from a 115 relative maturity to a 110 day on May 15 and lose 10 bushel.”  

Quinn also notes the caveat that corn hybrids mature in fewer growing degree days (GDDs) than predicted when planted "late." “We do a fair amount of planting date trials where we plant earlier into maybe cooler or more wet conditions versus where we wait a week or two and plant into much better conditions,” shares Quinn. “It's actually pretty surprising how fast that crop actually catches up because it has faster, more uniform emergence and then the yields end up being very, very good.”

Soybeans

The story is similar with soybeans. Stephanie Porter, outreach agronomist with the Illinois Soybean Association, notes that the highest yields are obtained from soybeans planted from mid-April until early May. “After mid-May, soybean yield potential can decline, on average, each day by about a half bushel per acre,” says Porter. “However, planting dates are not the only management decision that can lead to greater yield. Other management factors and Mother Nature determine yield potential during the rest of the growing season.”

Porter recommends that if both corn and soybeans still need to be planted, focus on finishing corn first. “Soybeans can adjust development due to late planting because they are photoperiod sensitive,” she says. “Soybeans are more apt to yield under stress when compared to corn.” 

As planting is delayed, Porter recommends increasing seeding rates by 10% if soybeans are still not planted by June. “This can help get to a greater number of nodes for trifoliate leaves to gather sunlight during a later growing season with shorter day length,” Porter explains. “More sunlight capture can allow for more branching and pods, which could lead to increased yield potential.”

Additional considerations for late planting

Porter offers some other management considerations for late planted soybeans to maximize return on investment in a season with tighter margins. “Fields that are not planted yet may be greening up now with summer annuals like waterhemp because our fall or spring burndown did not happen, or occurred earlier this spring,” she cautions. “Focus on these new weeds coming because they could haunt you the rest of the season. Another herbicide burndown with residuals may be needed depending on weed, label, and plant back restrictions before tillage or planting.” She also cautions to be cognizant of late postemergence or rescue herbicide applications to avoid the risk of carry-over into the next crop.

Porter also recommends paying attention to disease ratings of soybean varieties as adjustments to plant population and row spacing are made to compensate for late planting. “Increasing soybean population and decreasing row spacing can create a more favorable environment in certain weather scenarios for white mold, charcoal rot, stem canker, and possibly some leaf diseases,” says Porter.

Similar considerations should be made with corn as well. “Often if we plant later, the corn typically will go through more critical growth stages during periods of the year where we often have more stresses,” says Quinn. “Late planted corn might be tasseling at a time where we're getting a lot more disease coming in compared with corn that was planted a little bit earlier. It’s important to pay attention to the stress tolerance, disease scores, and insect tolerance of the hybrid and manage appropriately to maintain yield.”

Regardless of whether it’s corn or soybeans planted later, avoid the temptation to “mud in” planting. “You're still better off to wait,” cautions Gentle. “Mudding in just causes all kinds of problems. You can smear your sidewall or the furrow won’t get closed, which results in bad germination. Planting date is only one little piece of your ultimate yield at the end of the year. We still have a good two weeks before we're really starting to lose serious yield potential. I know it’s tough to wait another day or two, but let that soil get fit.”

Tools for decision making

Still unsure on the decision to change hybrids? Gentle recommends using the rain delay to play with online calculators. “We have a really good GDU calculator,” he shares. You can play with planting dates and pick our actual hybrids or pick maturity days and it will predict emergence, pollination, and black layer dates. Right now is a good time to plug in potential dates and see that you’re going to be OK.” 

Purdue offers a similar tool. “When you’re getting into mid-June where we get really concerned about having the corn crop mature, Purdue has the UTU Corn GDD decision support tool," shares Quinn.  “You can enter in your planting date, growing degree days from emergence to maturity, and it gives an idea on if you need to make changes to your hybrid based on first frost dates.”