Just How Cold was Friday Night & Saturday Morning?

Carrie Knott and Chad Lee, University of Kentucky, Grain and Forage Center of Excellence

Figure 1 Corn from Pulaski County where the growth above ground is displaying freeze damage. Photo from a farmer.

Freeze damage to crops occurs from a combination of cold temperature, the duration of the cold temperature and the crop growth stage. Matt Dixon, Senior Meteorologist with the UK Ag Weather Center, compiled temperatures across Kentucky.

Counties with at least 2 hours of temperatures below 30 F included Muhlenberg, Butler, Logan, and many counties east of these (Table 1). Carroll and Harrison both reported seven hours below 30 F and Harrison reported 5 hours below 28 F.  Other counties with five hours below 30 F included, Bullitt, Casey, Clark, Franklin Grayson. Lewis, Mason, Meade, Mercer, Owen, Owsley, Pike and Shelby. Many other counties mostly in central and eastern Kentucky reported temperatures below 30 F for at least 2 hours.

In all the counties with low temperatures, soil temperatures ranged between the mid-40’s to low 50’s. The soil should have insulated any crops below the soil surface or any growing points below the soil surface and prevented them from freezing.  

Air temperatures below 30 F for 2 hours or more likely damaged our wheat crop and may have damaged emerged soybeans plants and those in the 'crook' stage. These temperatures likely damaged the aboveground growth of corn, but the growing points likely survived and corn will most likely regrow. For corn, the growing point should be about an inch below the surface, if planting depth was proper and rows were closed properly. The soil should have insulated the growing points on corn. Soybeans have multiple growing points, but all of them were above the surface on emerged plants. Wheat was heading, flowering and filling seed, so temperatures at head height were most critical to those plants.   

While damage may be evident now (like these young corn plants from Pulaski County), we will need at least a week (7 days) to be able to assess the extent of the damage on wheat, soybeans and corn. Even though, it takes about a week, most of you are walking fields now. So are we! We will keep updating as the symptoms of freeze damage become more evident.

Figure 2 The mesocotyl from the seed to the soil surface is still turgid and appears healthy. Photo from a farmer in Pulaski County.