Historically low temperature effects on early planted soybeans and soybean planting decisions

Learn how the predicted low temperatures will affect planted soybean fields and soybean planting decisions over the next five days.

Soybean seedlings emerging from a field
Soybean seedlings emerging from a field planted on April 2, 2020. Photo by Mike Staton, MSU Extension.

Record setting low temperatures are predicted to occur through Monday, May 11, 2020, raising two important questions for soybean producers: Will early planted soybeans be damaged and should soybean planting continue despite the low temperatures?

Early planted soybeans will escape low temperature injury as long as the seedlings remain below the soil surface and have not emerged. Fortunately, the vast majority of soybeans planted in Michigan have not emerged and should escape injury. However, some fields that were planted in early April have emerged and will be vulnerable to injury from the low temperatures.

Typically, emerged seedlings in the VE to VC stages can tolerate temperatures of 29 to 30 degrees Fahrenheit. However, plants that have been exposed to low but non-lethal temperatures for several days become hardened and can tolerate temperatures down to 28 F for several hours. The bad news is that temperatures below 28 F are predicted to occur late Friday night and early Saturday morning throughout much of the state.

If you have fields where the seedlings have emerged, begin inspecting the plants for damage one to two days after the low temperature event occurred. Look for soft, sunken and discolored tissue on the hypocotyl and cotyledons. However, waiting at least five days following the event to inspect plants is recommended as new growth should be visible from the main growing point or the cotyledon node on viable plants. You can see photos from Purdue University at Symptoms of Low Temperature Injury to Corn and Soybean.

Planting into cold soil increases the risk of uneven or poor stands, so the decision about whether or not to continue planting despite the historically low temperatures is a highly personal decision. Consider the following when making this decision:

  • Your tolerance to risk.
  • How many acres need to be planted.
  • Current soil moisture conditions for planting.
  • The future weather forecast.
  • Is the seed treatment effective against pythium and sudden death syndrome?
  • Can you plant slightly deeper (1.5 to 1.75 inches deep)?
  • Are you planting high quality seed having intact seed coats?
  • Consider waiting until early afternoon to plant to allow the soil to warm.

In summary, most of the soybeans that have been planted should not be injured by the historic low temperature event. However, if you have questions about assessing the viability of a damaged stand, I encourage you to call me at 269-355-3376.

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