The soil in the garden is constantly being used over the year. Such repeated use makes it prone to weeds, fungal microorganisms, destructive pathogens, harmful bacteria and other garden pests that are injurious to the soil. If you choose to use the same soil over and over again without replacing it can cause these vile factors to grow in the soil. There are only two solutions to this problem.

First one is to replenish the soil and the second one is to sterilize it to disinfect and fumigate it. Such soil is going to serve the plant’s needs to the optimum. 

Here in this article we have to discuss the process of sterilization of the soil. 

What is soil sterilization?

soil sterilizationTo eliminate diseases and bugs from the soil commercial agricultural producers and greenhouses opt for the soil sterilization without considering its replenishing. You have to save your soil from the shabby look and destruction of the product by killing the little nasty things that grow into soil. 

Soil needs perfect condition to support the germination of the plants and grasses. This process is adversely affected by the gnats, no-see-ums, bugs, fungal pathogens and other microbes. It is specifically done by commercial landowners to have a perfect bug free harvest the next time. 

Ways to sterilize soil

Your garden soil and potting soil can be sterilized using two different methods. It can be 

  1. Chemical sterilization
  2. Heat procedure

Chemical Treatments

Considering soil sterilization on a large scale needs a great planning and management. This is opted by the commercial landscapers as it is easy to perform and is lighter on the pocket. This process is a speedy one even if there is a large landscape involved. So treating the soil with chemicals needs a secure plan. 

The fundamental rule behind the soil sterilization using chemicals is to produce gas that enters into the soil to execute annoyances, bacteria, bugs and other pathogens. 

There are both pros and cons of this method.


  1. It is attainable and feasible for the open fields and the gardens.
  2. It is economical.
  3. It takes less effort to carry it out. 
  4. Lesser labor is required. 


There are some major shortcomings and hitches in the chemical sterilization which make the chemical procedures less famous. 

  • Chemical uses cause health and safety risks. The person doing it is on a high alert even though he is wearing the proper kit and gear. It affects the other in the close vicinity as well. The toxic fumes from the chemicals cause diseases and other ecological issues. 
  • Recent chemicals have a very constricted affect. It is not the broad spectrum. It sometimes only target single type of pests. 
  • The soil is to be left untreated after the application called the quarantine period. If this time is not considered it is going to destroy everything in reach.
  • The improper application of the chemical causes adverse effects. It causes a potential threat to the plants and the soil.
  • Using chemicals over and over again can make it less effective and the pests stronger than before. 

Following are the types of chemical sterilization

1. Sterilizing Soil with Hydrogen Peroxide

Sterilization with hydrogen peroxide is the simplest of its kind. The landowner can simply do it himself. It does not require any technical procedure so one can easily do it. Its second advantage is that hydrogen peroxide is easily available in the market. Moreover, it is not that costly. 

There are several different solutions of hydrogen peroxide available for purchase. If the higher intensity of hydrogen peroxide is taken the lesser amount of the chemical will do the procedure. There are 3% and 35% solutions and both are equally good.  


  1. Add hydrogen peroxide to water to a desired amount. The amount of water and the chemical is prescribed. There are recommendations from the seasoned horticulturists and available online as well. 
  2. This water mixture is then directly sprayed onto the targeted soil.

This is simple and can be done on a large scale as well as on a small patch. 

02. Sterilizing Soil with Formalin

A mixture of water and formaldehyde is commonly known as Formalin. It is usually used to sterilize alfresco soil. It is mixed with simple water before application. It is quite effective against fungus but its effectiveness against gnats and microbes is not proven

The basic steps in using formalin are

  1. Water down the formalin. The ratio should be 1 part formalin 38% — 40%  to 49 parts water.
  2. Apply 5 gallons per square yard of formalin to the targeted soil in such a way that the soil gets completely soaked. 
  3. He soil is to be used after a month and a half after being decontaminated.
  4. This process requires a high temperature for vaporization and generating fumes.  

03. Sterilizing Soil with Other Chemicals

Sterilizing Soil with Other ChemicalsVarious other chemicals can also be used to sterilize the soil which are easily available to a layman.

Other chemicals are to be used on sterilizing the soil. These chemicals are to be used after the recommendations.   

04. Heat Treatments

The chemical procedures have many shortcomings which make the landscaper ponder over switching to other solutions.

Do we have any other solution?

Yes, we can treat the soil with a heat procedure.

In such a treatment the temperature of the soil is to be raised using steam or any other way to kill the unwelcoming guests of the soil. The harmful organisms, fungal spores, weed seeds, etc. are targeted in this process as they cannot stand that much heat and eventually die. Heat treatment is often referred to as sterilization, but this is a contradiction as the soil does not get disinfected entirely. 

Methods for Heat Sterilization of soil:

Choosing which method to steam or heat sterilize your soil is highly dependent on the amount of substrate you are working with, and how quickly you want the process done. The four common methods of heat sterilization different based on their heat source: boiling water/steam, a home oven, a microwave, or natural energy from the sun.


Sterilizing Soil with solar Soil solarization is an eco-friendly process of preparing the soil bed and make it free of germs, pests, unwelcoming plants and weeds, insects and all the other hostile and unfriendly factors out of soil.  The sun’s energy is harnessed using a specific method to sanitize it properly. 


  1. The desired patch is cleared of all types of trash. The debris is removed with rake. If there is waste or litter in the soil, it is to be removed with a garden hoe. 
  2. Drench the soil with plenty of water. Soak it so much that it becomes completely wet and a bit soaking. 
  3. Cover the marshy soil with a transparent plastic sheet. The mulching should be done with a clear and see-through sheet. The colored sheets will not do. The black, white, blue or any type of dyed and tainted plastic will not allow the shaft of sunlight to enter the soil as it should be.
  4. Bury the edges of the tarp properly. This step will not let the heat escape the corners. The heat stays inside making the thermal procedure more effective.
  5. Leave the tarpaulin in the same state for over 4 to 5 weeks or the desired time. Keep in mind that the desired weather for this process is the hottest of the summer. The sun beams heat up the muddy soil to such a heat that kills not only the microbes like bacteria, fungi, insects, nematodes, and mites but also the weeds and the weed seeds.
  6. The plastic is removed from the soil patch after the desired results are achieved. This plastic is then washed. It is hence quite economical for the business owner to adopt such practice.
  7. Once the soil bed gets back to the normal temperature, it poses to be the best patch to have the harvest.  

Boiling water or steam:

Condensation is an effective way to sterile the lawn soil. It can either be done with a pressure cooker or without it. If a pressure cooker is to be used, proper precautions are to be followed to avoid any mishap.  

 Pressure cooker method:

  1. Put required water and a stand in the pressure cooker.
  2.  Set thermal resistant heat-proof ampules or bowls on the stand. Fill each ampule with 4 inches of soil. 
  3. Seal the ampules with aluminum foil to capture the heat.  
  4. Seal the lid of the pressure cooker, letting the steam regulator open slightly. Then let the steam exhaust out to build a compression.
  5. Modify the heat according to the requirement. It will help building pressure.
  6. Progress with the soil at 10 pounds of pressure for 15 to 30 minutes after the closing of the steam spigots. 
  7. Switch off the heat source and let pressure reduce slowly.
  8. Use this soil. If not used immediately cover it with foil until being used. 

Non-pressurized container method:

  1. Put water in cooker and a stand in the container. 
  2. Fix thermal resistant containers on the stand containing not more than 4 inches of soil. 
  3. Seal the ampules or containers with foil. 
  4. Close with a lid but do not seal properly. 
  5. Let the water boil slowly for half an hour.
  6. Switch off the stove or heating source. 
  7. Use or set the soil aside sealed with foil until used. 


Oven sterilization is also a good way to go. There will be nasty stink in the kitchen during this process. So exhaust the place properly during the process. 


  1. Put 3 inches of soil in a container.
  2. Moisten the soil in such a way that it turns into steam. 
  3. Seal the container with foil and put it in a preheated oven at 200℉. 
  4. Keep a check on the temperature with a thermometer. Bake the soil at 180℉.

Switch off the oven and take the container out to let it cool down. 


Working with little amount of soil can be treated in a microwave. Inspect for metal and put the soil in the microwave.


  1. Take 1 kg of moist soil in a zip-top bag. The soil should be dampen only to create stem. 
  2. Open the bag from the Leave the top and place it in the microwave like is done to the food.
  3. Put your microwave on high until it reaches 180℉.
  4. Take the soil bag out and let it get cool to a normal temperature. 


Soil sterilization is used to eliminate bugs, weeds, pathogens and harmful bacteria from the soil. It is either done chemically or using the thermal procedures. It is done to give the next harvest a disease and microbe free environment to grow. 

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