Lester C. Fretz
Soil Sterilization for Indoor Planting
Although growing one’s annuals and vegetables indoors can be done easily and successfully, one limitation is the need to use sterile soil. Soil which is not sterile can result in importing unwanted insects into your home, disease and weeds. Sterilizing your soil is an easy and excellent way to avoid these problems.
Two convenient ways to sterilize amounts of soil sufficient for starting seedlings is the use of the micro wave or an electrically heated device common in most kitchens. Both methods simply involves heating the soil to 820 C.
To use the micro wave, place 1 Kg. of moist soil in a polypropylene bag leaving the top open for expansion and ventilation.. Heat the soil for 2 1/2 minutes on full power (i.e. 650 watt).
The photo illustrates using a kitchen appliance very readily and reasonably available at thrift stores. This one which measures 60 cm x 30 cm x 8 cm cost $4. Note the thermometer in the soil to ensure the correct temperature (820C or 1800F) has been reached. Once you determine the setting on your device, a thermometer is unnecessary.
Whether using a micro wave or a cooking appliance, do not prolong the cooking as it can affect the chemistry of the soil causing toxins harmful to the plants. Sterilizing kills the much needed important microbes however once plants are transplanted to the garden, the surrounding soil will soon spread its microbes to the newly planted plant.
Soil Sterilization may also reduce the possibility of blight.