Cleanliness and sterilization of materials is an important defense against plant diseases carried in soil and on containers. Sterilization kills disease organisms and many weed seeds.
Place the moist (but not wet) soil mix in an oven-proof container that can be covered to keep the soil from drying rapidly. If a cover is not available, cover with aluminum foil, and seal at the edges.
Pinch a small hole in the center of the foil and insert the bulb end of a meat or candy thermometer into the soil so that the bulb is about at the center of the soil mass. Place the pan in an oven at 200 to 250 degrees F. Keep the soil in the oven until the thermometer shows a temperature of 160 to 180 degrees F. Remove the pan and allow it to cool. Baking soil will give off a strong odor, so some ventilation may be desirable. The length of time necessary for sterilization depends upon the volume of soil, as well as its moisture content. Dry soil is difficult to sterilize. After the soil has been sterilized, make sure that containers, tools, and working areas are also clean and sterile. Clean soil can be easily reinfected by careless techniques.
