Sterilizing potting soil is a surefire way to destroy insects and diseases that may be lurking in the soil. You can pay a premium price to purchase sterilized potting soil from a nursery or garden center, or you can do it yourself at home using your oven for a fraction of the cost. No special equipment is needed; every thing you need is probably already in your kitchen.
Fill baking dishes or pans with no more than 4 inches potting soil in each pan.
Cover the pans tightly with aluminum foil.
Insert a meat thermometer into the center of one pan, pressing it through the foil and into the potting soil. If you do not have a meat thermometer, you can use a candy thermometer instead.
Place the pan in the oven, and heat the oven to 190 degrees F. You can set the oven higher, up to 250 degrees, if you will be able to watch the soil temperature closely as it cooks.
Bake the soil until the temperature on the thermometer remains at 180 degrees F for at least 30 minutes. Remove the soil from the oven after this time. The soil is now sterilized.