Soil Temperatures and Soybean Emergence

In our soybean seed size experiment we have been monitoring soil temperatures since planting on May 8th. Mean daily soil temperatures have ranged from 52 to 60 degrees F over this time. Preliminary research suggests that soybean requires ~145 (air) and ~165 (soil) GDD‘s base 50 degree F for emergence. The large difference between these two measurements is related to the temperature swing difference between air and soil temperatures in the spring. We have accumulated ~80 GDD based on soil temps since planting. This experiment is planted at Arlington WI on worked ground.