Similar to corn, soybeans need a good start to get a strong stand. Along with the field being “fit” for planting, the first 24 hours after being put in the ground are very important. Just like corn, soybeans can get chilling injury from a cold first drink of water, resulting in a reduced stand, and possibly needing to replant.
The following pictures tell a very good story to show the importance of the first 24 hours.
Warm Soils = Great Stand
In the above picture you can see a tray of soybeans that were planted into 25˚C soil and left at that temperature 17 days. There is an excellent stand and the soybeans are off to a great start. The key thing to note in this picture is that the soil was warm and kept warm.
Cold Soils = Uneven Emergence
This picture shows soybeans that were planted into soil at a temperature of 7˚C. It was kept this temperature for 20 hours then warmed up to 25˚C for 17 days. You can see a drastic difference in the emergence with only 3 plants at unifoliate, some at cotyledon stage, but a big portion of the seeds not emerged. The biggest take away that this picture shows is the soil was only at a the lower temperature (7˚C) for 20 hours! This illustrates that the first drink of water is crucial for the crop's success.
Warm Start = Good Start
In this last picture the soybeans were planted into warm soil (25˚C) and kept there for 8 hours. The soil was then cooled to 7˚C for 4 days. After that, the soil was again warmed to 25˚C for the remainder of the 17 days. Again you can see that the 1st drink of water for the seed is so important to the success of your crop. A couple plants are delayed, but in general these soybeans are established and will make a more than successful soybean crop.
Remember when planting this spring that the first drink of water your soybeans take is crucial to their development and success. Keep your thermometer handy!