Seth Naeve, Extension Soybean Agronomist, Jeff Coulter, Extension Corn Agronomist, Dave Nicolai, Extension Educator - Crops, and Phyllis Bongard, Educational Content Development and Communications Specialist

Figure 1. Frost effects on corn in Dakota County following a September 13th early morning frost indicating increased upper canopy damage in lower elevations of the field.
Many corn and soybean fields in central, west central, and southwest Minnesota were affected by frost during the morning hours of September 13, 2014. As is always the case, the frost damage appears to be highly variable based on local climate conditions, crop maturity, and topographical features. For corn, a killing freeze occurs when temperatures are 32°F for 4 hours or 28°F for minutes. A frost or killing freeze can still occur when temperatures are above 32°F, especially in low and unprotected areas when there is no wind. For soybeans, most reports indicated that the crop was unaffected, 'nipped' slightly at the tops, or (in rare cases) frozen down into the canopy.