How to Sterilize Your Homemade Potting Soil
Once you have made your own potting soil, you may want to sterilize it. Because the soil is made with decomposed matter and leaf mould, it is possible that it could contain contaminants and bacteria. By sterilizing it, you remove any harmful contaminants from the soil. Unfortunately, you also kill off most of the nutrients. You can sterilize the soil yourself in the kitchen, but you will want to add an organic fertilizer often to make sure your plants get all the nutrients they need.
There are two methods of sterilizing potting soil, and the method you choose is up to you. Both are effective and easy. The first method involves cooking the soil in the oven, while the second method uses the microwave. The microwave method is slightly quicker and uses less energy than the oven method.
Step 1- Preheat the Oven and Prepare the Soil
Preheat your oven to 180 degrees Fahrenheit. Pour your soil into the glass baking pans. The soil should be no more than four inches deep. Make sure it is spread out evenly in the pans.
Step 2- Cover the Pans
Cover the pans completely with aluminum foil. Fold the sides under carefully to make sure the aluminum foil stays in place. Stick a meat thermometer though the foil and into the soil in the middle of the pan. You only need to do this with one of the pans.
Step 3- Bake the Soil
When the oven reaches the appropriate temperature, insert the pans into the oven. Watch the thermometer. When it reaches 180 degrees, set a timer for 30 minutes. This is how long the soil will need to bake. Check occasionally to make sure the temperature doesn't go any higher. After 30 minutes, remove the pans and let them cool.
Step 4- Prepare Soil for Microwave Sterilization
If you decide to sterilize in the microwave, place the soil in a 2 lb. microwavable container with a sealing lid. A microwave safe plastic bag can be used in place of the container. Vent the container (the bag can be left open). You will need to use a microwave safe meat thermometer to monitor the temperature of the soil in the microwave. Every two pounds of potting soil you sterilize will need to be microwaved on high power for 90 seconds, or until it reaches the temperature of 180 degrees. You will need to keep it at that temperature for twenty minutes to properly sterilize it. After the time has elapsed, remove the containers and let the soil cool.
Step 5- Store the Soil
Which ever method you used, once the soil has cooled completely, it can be used. If you are not going to be using it right away, you will need to store it in a sterile, airtight container.