The USDA reports that 24% of the corn in KY is planted and 1% has emerged. The cold weather in the forecast could cause problems on this corn.
Corn that is trying to emerge (germinated and the shoot is growing towards the soil surface) is at greatest risk with the cold weather in the forecast. That cold weather could send shoots downward. These conditions often result in “corkscrew” plants that may not make it to the surface.
The germinating plant is relying on the seed for its energy until the shoot reaches sunlight and photosynthesis takes place. When the shoots corkscrew, the plant often runs out of energy before reaching the surface.
Corn that is emerged is at the least risk for damage from the cold weather in the forecast. We may see shoots clipped back to the soil surface, but those plants have a chance to send up new leaves. Whether or not they survive likely depends on how many days they conducted photosynthesis and whether there is enough energy remaining to send up new leaves.
Corn that is being planted today is at risk of taking in very cold water. The water temps are likely going to be below germination temps. Swollen seeds that are too cold to germinate often become dead seeds. If farmers are planting today and tomorrow, just have them be ready for replanting. They may escape and call us crazy later.
If they can, they want to pick seed that has high seed vigor. This rating does not appear on most seed tags. If they can get those numbers for their seed lots, then they can plant the seeds with the highest vigor. Seed vigor is an indicator of how well seeds germinate in stressful conditions.
Because they will not be able to get seed vigor numbers on many of their seeds, they probably should pick the seed that has the best replant offers.
We all will scout immediately and that will not tell us much. We need about five days of warmer weather and excellent growing conditions before we will know the extent of the damage and see signs of recovery.
You can reference this guide for more details: AGR-192: Evaluating Early Season Frost Damage in Corn.