The USDA NASS puts 4% of the soybean crop as planted by Monday of this week.
Soybean that has emerged is at risk of being frozen off below the cotyledons. If the plants are frozen off below the cotyledons, they will die. If the node at the cotyledon remains, they have a chance of surviving and recovering.
If after five days of excellent growing weather, new leaves are observed, those plants should make a full recovery and no yield loss is expected from those plants. Final stands of 70,000 plants per acre or more would not need to be replanted.
Soybean that is germinating has a shoot growing towards the soil surface. 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.
Soybeans being planted today are 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.
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.