Even the most experienced gardeners can have problems with pests, weeds, and diseases in their garden. These problems can crop 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 for sterilizing soil, but also how to sterilize soil.
What is soil sterilization
Soil sterilization involves 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 process of soil sterilization is often used by commercial greenhouses, farmers, and other agricultural producers and breeders because it is a preventative measure that is less costly than losing crops or treating problems when they arise.
Sterilize soil in the oven
If you only process small or medium-sized amounts of soil, for example if you want to sterilize potting soil, you can process it in the oven, which can hold several containers or trays at once. The disadvantage of this method, of course, is that the kitchen fills with the smell of the cooked earth. Therefore, you should ensure adequate ventilation. You will need a large oven-safe container, your soil, aluminum foil, an oven-safe thermometer, and water.
- Preheat the oven to 90 degrees Celsius.
- Fill the container with soil about four inches deep. Don't fill it too deep, otherwise the middle layer of soil won't get hot enough. Remove any stones or plant debris.
- Moisten the soil just enough so that it is completely moistened. The water creates steam that kills pollutants in the soil, but too much water slows or stops 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 for thirty minutes, keeping the oven door closed the entire time.
- Turn off the oven. Allow the soil to cool until it reaches room temperature.
Sterilize soil in the microwave
If you don't want to sterilize a large amount of soil or you don't have the time, you can also process it in the microwave. An unpleasant smell can also arise here, so make sure there is good ventilation. You may also consider temporarily moving your microwave outside or in the garage while you perform this routine. You will need a microwave, a plastic zip-top bag or container, a heatproof thermometer, soil, and water. Make sure the soil does not contain any metal parts.
- Fill the bag with moist soil. It should be moist enough to form clumps, but not runny.
- Do not close the bag or container completely, but allow the steam to escape to avoid pressure build-up.
- Place the container in the center of the microwave. Set the microwave to high. Because microwave ovens are different, actual processing time may vary. Heatthe earthcontinue until it reaches a temperature of 80 to 95 degrees Celsius.
- Once the correct temperature is reached, carefully remove the container and seal it. Let it cool down.
- 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 option for sterilization is to use boiling water or steam. This is a quick andeffective method. You can use a pressure cooker for this process. 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 cooker.
- Cover the containers with foil and place them in the pressure cooker.
- Place the lid on the pressure cooker.
- In order for the soil to be sterilized, it must be worked for 15 to 30 minutes.
- Turn off the heat and allow the pressure to release according to the instructions on your pressure cooker.
- Once the soil has returned to room temperature, it is ready for use. You can also keep them tightly covered until ready to use.
Sun sterilization method
This method works by exposing the earth to sunlight by covering the earth with layers of plastic. The heat from the sun increases the temperature of the soil and kills most bacteria, diseases, weeds and pests. Sterilization by solarization can be done in different ways:
When 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,thus the earthforms a thin layer of a few centimeters. 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. Of course, this process requires strong, direct sunlight for as long as possible. Clear or transparent plastic is best as it heats up quickest and allows direct sunlight to penetrate the soil. Very thin plastic heats up quickly, but is susceptible to damage and cracks. We therefore recommend a medium-thick, good quality film that can then be washed, folded and reused another day.
- If possible, buy the plastic sheeting in large sheets and find a few stakes or rocks to hold them in place so that it doesn't blow away or the cool wind creeps under the edges and cools the ground.
- Break up any clods of soil and remove any plant debris and large stones that could tear the film or slow down the process.
- Moisten the soil until it is slightly damp. When solarizing the soil in a garden or field, you need to ensure that the top layer of soilis moist,before starting the process. Water it or start after rain.
- Cover the prepared base with plastic wrap, making sure it is flat. You can also bury the edges of the foil underground to seal in the heat build-up. 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 around four to six weeks for the solarization process to complete on large areas. It may take longer in cooler conditions.
