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Spring frost

Spring frost rarely damages soybean in Minnesota, as the last average frost dates usually occur before producers normally plant soybeans.

However, when soybean planting and emergence is well ahead of the five-year average, the crop becomes more vulnerable to early season frost events. If temperatures drop into the low 30s and upper 20s, emerged soybeans will likely experience some degree of frost injury.

In University of Minnesota planting date studies conducted in Lamberton since the 1980s, frost has rarely injured stands planted April and later. However, when injured, stands were not reduced to a level where replanting would be recommended. The injured stands still yielded as well as later, unfrosted dates.

Factors affecting survivability

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Assessing frost injury

Soybean frost injury appears as water-soaked lesions on the cotyledons, leaves or hypocotyl that dry and turn brown after several days. Photo gallery: Symptoms of low temperature injury to corn and soybean.

Before assessing frost damage, wait three to five days to allow the soybean plants to show signs of new growth. Check for firm, healthy stems, cotyledons and growing points. At this point, you should be able to tell whether the soybeans are recovering or dead.

If a significant proportion of the population is dead, replanting may be justified. Guide to evaluating soybean damage and deciding whether to replant.

Managing frosted soybeans

Freeze injury is a traumatic physiological event for the plant and can slow soybean development for several days.

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Bruce Potter, integrated pest management specialist, Southwest Research and Outreach Center; Phyllis Bongard, Extension communications specialist; Seth Naeve, Extension agronomist and Jeff Gunsolus, Extension weed scientist

Reviewed in 2018

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