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Sterilize soil for houseplants and in the garden: effective methods + step by step instructions!

Even the most experienced gardeners can have problems with pests, weeds and diseases in their gardens. These problems can pop up unexpectedly, leaving frustration and disappointment when gardens and houseplants fail. One method to prevent this is soil sterilization. There are a number of different methods you can use. Below we will discuss not only the reasons to sterilize soil, but also how to sterilize soil.

What is soil sterilization

Soil sterilization kills weed roots, soil mites and other pests and bacteria

Soil sterilization is the process of killing weed roots, soil mites and other pests, viruses, fungi and bacteria in the soil to prevent them from destroying your crops and plants. The soil sterilization process is commonly used by commercial greenhouses, farmers and other agricultural producers and growers because it is a preventative measure that is less costly than losing crops or treating problems when they occur.

Sterilize soil in the oven

If you are only processing small or medium amounts of soil, such as when you want to sterilize potting soil, you can process it in an oven that can fit several containers or trays at once. The disadvantage of this method, of course, is that the kitchen fills with the smell of cooked soil. Therefore, you should provide adequate ventilation. You will need a large oven-safe container, your soil, aluminum foil, an oven-safe thermometer and water.

If you are only processing small or medium amounts of soil, you can process it in the oven

  • Preheat the oven to 90 degrees Fahrenheit.
  • Fill the container about six inches deep with soil. Don’t fill it too deep or the middle layer of soil won’t get hot enough. Remove any rocks or plant debris.
  • Moisten the soil just enough so that it is completely saturated. The water creates steam that kills the contaminants in the soil, but too much water will slow or stop the process.
  • Cover the container with aluminum foil to prevent the soil from drying out before the sterilization process begins.
  • Measure the temperature with a heat-resistant thermometer. Once the temperature of the soil reaches 80 degrees Celsius, bake it for thirty minutes, keeping the oven door closed the entire time.
  • Turn off the oven. Let the soil cool until it reaches room temperature.

Sterilizing soil in the microwave

If you do not sterilize a large amount of soil, you can also process it in the microwave oven

If you don’t sterilize a large amount of soil or you don’t have the time, you can also microwave it. Again, this can produce an unpleasant odor, so make sure it is well ventilated. You may also consider temporarily moving your microwave outside or into the garage while you do this routine. You will need a microwave, a plastic zipper lock bag or plastic container, a heat resistant thermometer, soil and water. Make sure the soil does not contain any metal particles.

Sterilize soil - Once the soil has returned to room temperature, it is ready for use

  • Fill the bag with moist soil. It should be moist enough to form clumps, but not liquid.
  • Do not seal the bag or container completely, but allow steam to escape to prevent pressure buildup.
  • Place the container in the center of the microwave. Set the microwave to the highest setting. Since microwave ovens vary, the actual time of processing may vary. Continue heating the soil until it reaches a temperature of 80 to 95 degrees Fahrenheit.
  • Once the proper temperature is reached, carefully remove the container and seal it. Allow it to cool.
  • Once the soil has returned to room temperature, it is ready for use. You can keep the container sealed and store the soil for later use as long as you keep the bag sealed.

Steam disinfection is another method

Another way to sterilize is to use boiling water or steam

Another way to sterilize is to use boiling water or steam. This is a quick and effective method. You can use a pressure cooker for this procedure. However, make sure you follow the instructions for your pressure cooker and always be careful. You will need a pressure cooker with a rack, heat resistant containers that are safe to use in the pressure cooker, soil, aluminum foil and water.

  • First, place your pressure cooker in a safe place. Add a few cups of water and the rack.
  • Fill the containers with soil to place in the stove.
  • Cover the containers with foil and place them in the pressure cooker.
  • Put the lid on the pressure cooker.
  • For the soil to be sterilized, process it for 15 to 30 minutes.
  • Turn off the heat and release the pressure according to the instructions on your pressure cooker.
  • Once the soil has returned to room temperature, it is ready to use. You can also store it tightly covered until ready to use.

Sterilization method in the sun

This method works by exposing the soil to sunlight, covering it with plastic layers

This method works by exposing the soil to sunlight by covering it with layers of plastic. The heat of the sun raises the temperature of the soil and kills most bacteria, diseases, weeds and pests. Sterilization by solarization can be done in several ways:

If you are sterilizing small amounts of soil, you can use plastic bags to create a mini-greenhouse effect by placing the bag in strong sunlight. It is important that you lay the bag flat so that the soil forms a thin layer of a few inches. For large areas, you can try shoveling the soil in thin layers between large sheets of clear plastic. The basic principle is to warm the soil so that thinner layers work better.

If you want to sterilize entire beds or gardens, simply cover them with plastic wrap and let the sun heat them up. This process, of course, requires strong, direct sunlight for as long a period as possible. Clear or transparent plastic is best, as it heats up the fastest and allows direct sunlight to penetrate the base. Very thin plastic heats up quickly but is susceptible to damage and cracking. Therefore, we recommend a medium-thick film of good quality that can then be washed off, folded and reused another day.

Step-by-step instructions for garden soil disinfection.

Follow our step-by-step instructions for garden soil sterilization

  • Buy the plastic sheeting in large sheets, if possible, and find some stakes or rocks to secure it so it doesn’t blow away or allow the cool wind to creep under the edges and cool the soil.
  • Break up any clumps of soil and remove any plant debris or large stones that might tear the liner or slow the process.
  • Moisten the soil until it is somewhat moist. If you are solarizing soil in a garden or field, make sure the top layer of soil is moist before you begin the process. Water it or start after rain.
  • Cover the prepared soil with plastic wrap and make sure it is flat. You can also bury the edges of the plastic wrap under the soil to seal in the heat buildup. If you use plastic bags, make sure they are tightly closed and the soil is spread in a thin layer.
  • During the hottest time of the year, it can take about four to six weeks to complete the solarization process on large areas. In cooler conditions, it may take longer.