A large number of farmers in the Pee Dee use reduced till or no till practices in their fields. This leaves more crop residue in the fields that creates a pretty decent barrier for weeds, slows the evaporation of moisture, and it also affects the temperature of the soil. A layer of crop residue insulates the soil much like the insulation in the walls of a house. It slows the warming of the soil when the weather is warm and the cooling of the soil when the weather is cold. Take a look at the picture below. As you can see, there is little residue on the ground around the thermometer.
The thermometer in this spot is reading 62 degrees.
About 20 feet away in the same field, there is a heavy layer of soybean residue.
The thermometer in this spot is reading 53 degrees. There is a 10 degree difference between the two spots.
The soil under the heavy residue is definitely warming up more slowly than the bare soil. This time of year farmers are getting ready to start planting corn. We want to wait until the soil temp in the rooting zone (2″) has averaged 55 degrees for at least 3 days. Planting in soil too cool will slow the growth of the seedlings. Farmers in fields with heavy residue from their previous crop or from a cover crop may need to wait a few extra days to plant to allow the soil to warm up more.