Ten points about soybeans and frost

Frost isn’t necessarily a death knell for soybeans

Worried about a forecast frost for later this week? It’s worrisome, but it doesn’t mean an absolute disaster for soybeans. 

It depends on what growth stage they are in and conditions like soil moisture, soil type, and previous crop residue.

Here are 10 things to consider from Bruce Potter, a University of Minnesota integrated pest management specialist. 

  1. Unlike soybeans, the growing point of emerged corn is still below the soil surface and protected from frost.
  2. Soybeans that have not emerged (including hypocotyl crook) will be OK. In a North Dakota State University study, 50% of seedlings were able to tolerate temperatures as low as 24°F. for a short time. In this same study, peas were similar to soybeans, edible beans were less tolerant, and alfalfa was more tolerant to frost. 
  3. Soil moisture, soil type, and previous crop residue can influence freeze tolerance.
  4. Plants with a live growing point remaining can survive.
  5. Plants frozen below the cotyledons will be dead.
  6. Yield loss will be related to stand loss, and soybeans compensate well for reduced stands.
  7. You will need to wait several days to adequately assess stand loss.
  8. Soybean injury or death from freezing temperatures is more likely in low areas.
  9. Soybeans in the cotyledon stage are more freeze-tolerant than in later stages.
  10. Temperatures will likely need to drop below 32°F. for soybean seedlings to be killed.
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