Effects of an Early Season Frost

With temperatures dipping down to the freezing mark and lower Friday night to early Saturday, I thought it would be good to cover the potential effects of a frost on this 2020 crop. Both corn and soybeans should be able to handle a light version of a frost without too many ill effects. I consider a light frost to consist of temperatures ranging from 30-32 degrees for 1-2 hours. It is possible in this scenario for corn growth to be damaged but if the plant is small (v1-V2) it should make a full recovery due to the growing point still being below ground. Soybeans can usually handle a frost better than corn if both are emerged. A light frost could damage the first true leaves of a soybean but likely not damage the soybean cotyledons. Remember the cotyledons on a soybean plant serve as the growing point.

If temperatures stay in that 30-32 degree range for a prolonged period of time (3-4 hours or longer) or a hard freeze occurs, this is where the real threat could lie. With our ground being as wet as it is in central Illinois, I would not expect a hard freeze to affect anything that is not already emerged. However, dry soil will allow a freeze to go deeper. If you are in an area with dry soils, a prolonged hard freeze could be an issue if corn sprouts are within ½” of the surface. Soybeans in this scenario should fare much better. The soybean cotyledons and hypocotyl are much tougher and resilient than a young corn seedling. Any emerged corn during a hard freeze will likely be burnt to the ground but if the corn has not reached that v4 growth stage, I would suspect it to make a full recovery. Emerged soybeans during a hard freeze should survive if the cotyledons are not permanently damaged.

You will be able to tell if corn has been hit with a frost within the first 24 hours. Corn will turn dark green then will wilt and turn pale. Soybeans will start to show damage within the first 24-48 hours after a frost, but it will take up to five days before any real assessment of the crop can be made. If new growth in soybeans has not occurred within 7-10 days after a hard frost, then decisions will need to be made for replant. For any wheat crop, I would wait for 5 days then go split some stems and examine the seed heads for damage.

Our best friend for dealing with a frost would be for the winds to pick up and cloudy conditions to occur. If it stays clear and still, this is when a frost would likely hit. Hopefully, we can get through this weekend without too much damage and continue onward with the 2020 crop. Stay safe and stay healthy!

Derek

Illinois Sales Manager

309-267-6905