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What Now for Soggy and Chilly Fields?

Imbibitional chilling is a concern. Still, warm subsequent temperatures can help ease worries.

Given the rain, snow, and bone-chilling temperatures that swept across the Midwest and Great Plains late last week and this weekend, you’re probably wondering this: Is the corn I planted going to be OK? 

That’s a valid concern. Here’s some of the information that’s passed across our desks the past few days on this topic.

Soil Temperature is Big 

In a newsletter to his southern Minnesota customers, Jay Zielske, an account manager for DuPont Pioneer, notes that cold weather brings with it concerns about imbibitional chilling injury. Damage from the seed imbibing cold water runs the gamut, from seed death to maladies like corkscrews or fused coleoptiles. 

“It definitely is a phenomenon that can occur,” he writes.  “However, its occurrence isn’t always predictable as numerous factors come into play.” 

The magic number when it comes to imbibitional water uptake is 50°F., note University of Nebraska (U of N) agronomists and Extension educators.

Once planted, corn seeds need a 48-hour window when the soil temperature at planting depth does not drop much below 50°F. Below 50°F., potential exists for chilling injury to affect seed germination and seedling growth. Soil temperature decreases after this time are less likely to affect seed germination.  

The U of N scientists note that debate exists about what specific temperature and timing causes imbibitional chilling. If temperatures dip down to the low 40s in the first 48 hours after planting, seed chilling risk is high. Some scientists suggest that corn will not be injured at soil temperatures as low as 41°F. However, injury risk from imbibitional chilling at those low temperatures still exists. 

What About Soybeans?

Compared with corn, the imbibitional phase — where a fast uptake of water occurs — is shorter in soybeans than in corn. 

Compared with corn’s 48 hours, soybeans’ 24-hour imbibitional phase is shorter. That’s a narrower window in which a cold rain or snowfall after planting can lead to soybean chilling injury and thus lower stands.

Saturated soil with cold temperatures significantly reduces germination rate. Thus, fungicide seed treatments are recommended if planting soybeans in April or early May.

What to Do? 

In areas where water has ponded, several days will be needed before fields are fit to work and plant, says Kent Thiesse, farm management analyst and vice president of MinnStar Bank. The good news: Long-range forecasts call for drier and warmer weather in that area. 

That’s why it pays to be patient if you still have corn acres to plant, he adds. Considering high seed costs and limited availability of top hybrids, most farmers don’t want to take the risk of planting corn into poor soil conditions, says Thiesse. Warmer and drier temperatures should snap back soils into good shape for planting.

Once soils are fit to plant, do it and worry about applying nitrogen (N) later, says Zielske. Multiple application options exist. These can include:

  • Topdressing with urea and AMS. 
  • Blind sidedressing anhydrous ammonia before corn has emerged.
  • Traditional sidedress timing. 

In his area, Zielske recommends having a base rate of N as 28% or 32% as a carrier for a preemerge herbicide application. Ten gallons (per acre) of 25% as a carrier will provide nearly 30 pounds of nitrogen (per acre), allowing for a reasonable window to apply your remaining nitrogen needs. 

Be Patient

In southern Minnesota, the sweet spot for timely corn planting ranges from April 20 to May 7. Still, yield potential reduction is minimal from May 5 to May 15 in southern Minnesota, and depends on the season’s growing weather, says Thiesse. Even corn planted from May 15 to May 25 has a good chance of producing 90% to 95% of optimal yield potential, assuming that favorable growing conditions result in 2017. 

This upside applies to soybeans, too. The ideal window to plant soybeans and obtain optimal yields in southern Minnesota and northern Iowa extends until about May 25. Thus, there is plenty of time to get the 2017 soybean crop planted, says Thiesse.

Some Minnesota farmers may remember the first week in May 2013, when farmers in the southern Minnesota areas of New Richland, Waseca, and Owatonna areas planted corn a day or two ahead of 10 to 13 inches of snow. Subsequent warm temperatures then occurred. 

“Some of the best corn that year came from corn planted immediately ahead of the snowstorm,” writes Zielske.

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