When you use potting soil for starting seeds or planting plants, sterilized soil is the soil of choice for best growing results. Sterilized soil is free of pathogens that could harm your plants and affect your success. While you can purchase sterile potting soil from any garden center, you can also make your own sterile potting soil.
Moisten the soil evenly with water so that it will hold its shape if you compact it in your hand.
Fill the plastic food bag with 2 lbs. of moist soil. Leave the bag completely open.
Place the open plastic bag into the microwave oven.
Set the microwave to full power and microwave the soil for 1 1/2 to 2 1/2 minutes.
Close the bag and leave the soil undisturbed until it cools completely.
Remove the soil from the bag and use it for planting your seeds or plants.