I need to sterilize the ground
Removed burning bushes after they died. They showed dying leaves and no growth. There were white areas on the stems. They were 20 years old. Want to plant new burning bushes in the same place where we just took them out. There are some roots still low in the ground.
I would dig up as much of the old roots that you can remove from the soil.
Here is a link that will explain solarization of a garden bed.