Waiting Periods for Sterilizing Soil

Zap It

• Microwave oven sterilization of soil is one of the quickest, easiest methods available. Place 2 pounds of damp, not wet, crumbly soil into a plastic container. Choose a container with a well-fitting lid in which you can poke holes for ventilation. Place the ventilated lid securely on the container and place it in the microwave. Microwave the soil-filled container for 90 seconds on maximum power to sterilize the soil. Do as many batches as are necessary to sterilize all the soil, allowing it to cool thoroughly before use.

Something's in the Oven

• You can also use an ordinary kitchen oven to sterilize soil in larger quantities than you can process in a microwave. Preheat the oven to 200 degrees Fahrenheit. Fill a metal baking pan with soil no more than 4 inches deep. Cover the pan securely with a sheet of aluminum foil. Check the soil temperature with a cooking thermometer. Once it reaches 180 degrees F, allow it to bake for 20 minutes. Cool the soil and keep covered with foil until you begin planting.

Turn up the Pressure

• If you own and know how to safely use a pressure cooker, you can sterilize soil on top of the stove. Fill the pressure cooker half full with water. Insert a rack above the water and put an aluminum-covered, soil-filled container on top of it. With the steam valve open, allow the air to escape. Close the valve and cook the soil at 10 pounds pressure for 15 minutes. Remove the pressure cooker from heat, allow the pressure gauge to drop back to zero before opening, and cool the soil container thoroughly before use.

All Steamed Up

• If you're not comfortable using a pressure cooker or simply don't own one, you can still use steam without pressure to sterilize soil. Fill the bottom of a Dutch oven with 2 inches of water. Insert the rack and put a soil-filled container covered with aluminum foil on top of the rack. Bring the water to a boil over medium heat and watch for steam to escape the lid vents. Boil for a full 30 minutes once steam has been started. Remove the pan from the heat and allow it to cool thoroughly at the end of the sterilization process.