How To Sterilize Soil And Know You’ll Only Grow Happy Plants?

If you are into gardening or the business of growing plants and crops for commercial purposes, taking care of the soil you use to grow your essential crops is a must. When you keep using the same soil repeatedly over and over again to grow the crops, there may be a build-up of weed seeds, harmful pathogens, fungal spores, and other kinds of harmful garden pests. If you cannot afford the time and effort to replenish the soil before using it again, it’s recommended to sterilize the soil periodically. But how to sterilize soil? Let’s dig deeper.

Sterilizing the soil your growing in is one of the best ways to make sure your soil remains healthy for every season of crop or for every plant you plan to grow in that soil. In this piece, we will talk about everything you need to know about soil sterilization, why you should do it, how to sterilize the soil for houseplants, and the various soil sterilization methods.


Soil Sterilization Definition

Sterilization of soil is one of the most popular processes that has been used for a long time for commercial purposes, such as in greenhouses or by commercial agriculturists. In the greenhouses, it is done so they wouldn’t have to replenish the potting soil year after year.

The farmers and the commercial agriculturists use soil sterilization when faced with increased pests and diseases in crops with high commercial value.

Soil Sterilization Is Prevention

Sterilization as a process is far cheaper than treating plant diseases and problems one at a time, leading to considerable losses to the entire crop. Sterilization is such a proactive measure to ensure your plants grow well.

As they say, prevention is better than cure; sterilization is always better when it comes to prevention. Agriculturists and gardening experts resort to soil sterilization as a tried and tested method of protecting the crops and keeping their plants healthy.

Some experts believe that soil sterilization is a must. It plays a significant role in using the soil to germinate the seeds, stem propagation, shoot cuttings, or transplanting juvenile plants.

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When You Grow From Scratch

The ground is more vulnerable and susceptible to fungal spores, mold infections, or many harmful organisms during these growing conditions. Soil sterilization is not that important when you are growing mature plants. But, when it comes to growing a plant from scratch that involves seeding, germinating, and all other processes mentioned above, it is highly beneficial.

But, there are mixed opinions of using soil sterilization by homeowners or other small gardeners. Some believe that it is not worth all the time and effort that it takes for the minimal benefits it gives. Some feel that soil sterilization can impact the soil negatively and wipes the soil off valuable microorganisms. At the same time, many think that soil sterilization is critical for good plant growth.

There are obvious pros and cons when it comes to soil sterilization. But thankfully, we can minimize the harmful effects if we follow appropriate procedures. Let's now learn what soil sterilization is all about.

What is Soil Sterilization?

Soil sterilization refers to how disease-causing microorganisms in soil are destroyed or killed without affecting or causing harm to the plants. In other words, soil sterilization involves the various methods in which soil-loving organisms that dwell in the soil can extract all the essential nutrients from the ground and wreck the crops.

We can use many methods and procedures to sterilize the soil, which involves doing it through chemical procedures or natural processes. Soil sterilization generally changes the properties of the soil but also eliminating harmful microorganisms.

Chemicals used in sterilization selectively destroy the harmful organisms and affect only particular diseases without causing harm to other organisms that are useful for the ground.

There are many different ways to sterilize the soil, and in this piece, we will walk you through some of these ways.

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But Do Plants Grow Better In Sterile Soil?

This is an obvious question when we talk about soil sterilization. The sole purpose of sterilization is to make sure your plants grow better in the soil. When you are sterilizing the soil, you are making it free from harmful organisms. You’re also making the soil free from all weeds that steal nutrients from the ground.

When you make the soil sterile, you selectively destroy the harmful organisms in the soil while the good organisms continue to live. This ensures that an ideal growing environment or soil bed is made available to your plants, ensuring healthy plant growth.

When you grow in healthy soil, the plants get all the essential nutrients uninterrupted. In addition, the absence of harmful disease-causing microorganisms ensures that the soil is disease-free, which is vital for healthy growth. And finally, the good microorganisms that are allowed to thrive in the ground ensure that the nitrogen fixation and other processes happen smoothly so that the plant is healthy.

So, to answer the question of whether plants grow better in sterile soil or not is Yes! Your plants would grow better in clean soil. This is because the absence of harmful microorganisms, and unwanted weeds, make an ideal growth environment.
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Should I Sterilize Potting Soil?

When you are thinking of creating a little plant corner inside your home, you have no other option but to grow in pots. So, if you use old potting soil, you need to ensure that it’s free from harmful microorganisms or unwanted weeds. You must ensure you are sterilizing the used potting soil to create an ideal soil bed for planting your plants and seeds. This is a great way to ensure your plants grow to be healthy.

So if you decide to use the same soil, you should sterilize it to get away from harmful microorganisms and weeds and provide an ideal environment and solid bed for your new plants.

The potting soil mixes you can buy from the nurseries are made from clean ingredients and don't usually need sterilization if the seller has composted it. I mean that if you only have a small amount of soil, sterilization might not be a wise choice.

Why Do We Sterilize The Soil?

This is an interesting question, and even though we already talked about how soil sterilization can help in the healthy growth of your plants. But in this section, let’s find out about the reasons why you should sterilize the soil:

1. Let’s Get Rid Of The Weeds

Soil sterilization will remove/destroy unwanted weeds. Many unwanted plants grow in the soil, which we tend to call weeds. These weeds may also steal nutrients from your plants, thereby draining the soil out of the ones your plants need. Hence sterilization will ensure that the weeds and unwanted growth won’t become a problem so that your plants can thrive.

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2. Let’s Also Remove The Harmful Bacterias And Pathogens

It’s crucial to make the soil free from disease-causing bacterias and pathogens. Apart from soil-loving organisms and unwanted weeds, some soil pathogens may cause diseases to your plants.

The most common pathogen types that can cause harm in plants include bacteria, fungi, mollicutes, parasitic algae, protozoa, nematodes, viroids, and viruses.

You can remove all these pathogens only with the help of sterilization, and as such, once done, you have pathogen-free soil. This, in turn, ensures you can grow healthy plants.

3. Let’s Make Sure That Pests Don’t Harm Our Plants

Lastly, let’s make the soil free from harmful pests and insects. You may have observed pests and small insects that are dwelling in the ground. While some of these insects are good for the soil/plants, some may harm soil fertility.

For example, the dead remains of all insects help to improve the fertility of the soil. Unfortunately, some pests can damage your plants and cause huge losses. So, when you sterilize the soil, you make it free from pests and insects and promoting healthy plant growth in the long run.

Having answered some of the fundamental questions on what it is and why to do soil sterilization, let us examine how to sterilize soil using different methods.

How To Sterilize Used Potting Soil?


Let us begin by learning how to sterilize used potting soil.

  1. First, take out the soil from the pot. Ensure that it is moist enough so that you can quickly make it into a ball with your hands. Do that by adding some water to this potting soil mix.
  2. Place the soil in a pan or on a baking sheet.
  3. Distribute the soil evenly on the pan or the baking sheet and remove any lumps.
  4. Pack the pan or the sheet covering the top tightly with aluminum foil. This foil needs to be tight so that we can prevent any loss of moisture or burning.
  5. Make a hole in the center of the foil where a thermometer can pass through.
  6. Put the pan or the baking tray in the oven at 180°F (about 82°C). If you exceed this temperature, it may burn the soil that may cause severe alteration to the soil’s chemical composition.
  7. Keep the soil at this temperature in the oven for thirty minutes.
  8. Remove it and keep it at room temperature until it has cooled down.
  9. The potting soil is now sterilized, and you can use it!

How To Sterilize Soil In The Oven?

We got a glimpse of how you can sterilize soil by using an oven. In general, you can sterilize any soil in the oven. To do that:

  1. Fill some soil into an oven-safe container. This container can be a glass container or a baking tray.
  2. Cover and seal this container tightly with aluminum foil. While doing that, you will need to ensure there is a hole in the center to place the meat thermometer for checking the temperature.
  3. Place the glass container or tray inside the oven with the thermometer placed in the center. This is to ensure you know the temperature at which the soil is being heated.
  4. Heat the soil at a temperature of 180 to 200°F (about 82 to 93°C) for thirty minutes. Make sure you do not exceed the temperature beyond that. Going beyond that temperature can burn the soil leading to alterations in the chemical composition and may even lead to toxins.
  5. Take out the tray and allow it to cool down to room temperature.
Microwaves from the oven ensure the water in the soil absorbs all the heat well, thereby killing all the microorganisms.

How To Sterilize Soil Without Baking It?

If you don’t want to use the oven for soil sterilization, you have better options as well. You can opt to sterilize the soil by using steam! Steaming works best with potting soil because it has fewer impurities and pathogens, and you can easily handle it. To sterilize soil using steam and not bake it, you can use a pressure cooker or even work without it. You’ll need to:

  1. Pour a few cups of water into the pressure cooker (if you use one).
  2. Place the soil above it (using a rack). Make sure the valve is left open so that the steam can escape. You can place the soil in a container packed with aluminum foil or glass beakers, Petri dishes, steel trays, etc. Or, you can use a regular container with water filled in it and rack on top of it with a lid slightly open for the excess steam to pass.
  3. Steam the soil at 250°F (about 121°C) for about 20 to 30 minutes, but the longer, the better. So keeping it for one hour would be ideal. This process is also known as autoclaving, and it’s recommended to spread the soil in thin layers for the best results.

How To Sterilize Soil With Boiling Water And Why Boiling Water?

The following most commonly used heat sterilization method is to use boiling water. Heating water at the boiling point is known to kill all the harmful bacteria and pathogens in the water. The same is true for the soil as well.

This means that when you boil water at 212°F (100°C), it can kill all the pathogens and organisms in the soil. This temperature range is instrumental in sterilizing soil as such a high-temperature range is highly effective. To sterilize soil using boiling water:

  1. Add the amount of dirt that you need to sterilize in a container.
  2. Pour piping hot boiling water into the soil.
  3. Work it around using a spoon or a spatula or anything else that you find convenient. The boiling water will kill all the organisms, insects, and pathogens in it.
  4. Once done, drain out the excess water from the container and allow the soil to dry at room temperature.
  5. Once dried, this soil is fresh and ready for your new plants.
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How Do You Sterilize Soil In The Sun?

This process is also known as “solarization” and is more common when sterilizing garden soil. In this process, as the name suggests, heat from the sun is used to sterilize the soil. The principle behind the solarization technique is to use solar heat to heat the ground and kill harmful pathogens and microorganisms.

What Material To Use For Soil Solarization?

You will first need to get some plastic sheets big enough to cover the soil area you wish to sterilize. The thickness and color matter a lot. Make sure you get a clear and transparent plastic sheet of medium thickness. This ensures the heat is absorbed well by the soil.

How Long Does It Take To Solarize Soil?

The next step is to irrigate the top layer until the soil is moist. Remove all the clumps and litter you can, and cover the ground with the plastic sheet tightly. To ensure they are tightly bound, you can use bricks and rocks towards the edge of the sheets to keep them from flying away. Keep it like this for three to four weeks during the hottest days of the year, and the resultant soil will be sterilized and ready for use.

How Do You Sterilize Soil With Hydrogen Peroxide?

If you are reusing a potting mix or are simply looking forward to sterilizing some garden soil, you can opt to treat it with hydrogen peroxide as well. This ensures that any fungal growth or bacteria prevalent in the ground is eliminated with ease. This is a chemical sterilization method, and as such, getting the mixture right plays an instrumental role.

Use a pint of 3 percent hydrogen peroxide solution in 1 gallon (about 4 liters) of water. Once the mixture is ready, soak the bottom of the plant directly with the solution in the evening and allow it to sit overnight.

How To Sterilize Soil To Stop Any Growth Completely?

Someone Holding Mulch In Their Gloves
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You can even sterilize soil so that nothing grows in it. Do this by using weed killers, vinegar solutions, prolonged solarization, or mulch. You can use all these techniques to sterilize the soil permanently and avoid any growth. Salt treatment is also one of the tried and tested methods. You can use one of these methods to kill all vegetation.

Does Soil Sterilization Remove Nutrients From It?

This is a common question amongst first-timers and home garden enthusiasts. Sterilizing the soil ensures that the plants you plan to grow get the needed nutrients in ample amounts and avoid unwanted parasites, organisms, pathogens, and weed growth.

Most of the soil sterilization methods are safe and don't remove the nutrients from the soil. But one must exercise caution and follow the proper procedures to ensure the ground doesn't get adversely affected.

Final Words

To conclude and summarize, we can say that soil sterilization is an effective way to ensure you grow healthy plants. In a sealed package, it ensures that the soil nutrients meant for your plants don’t get depleted by the parasites and microorganisms living in the soil.

It is also required to make sure your plants do not get one of those severe plant diseases that may hamper or even kill them. Soil sterilization as such is an excellent practice. So, use this piece to know everything about soil sterilization and more!

Featured image credit – Wstockstudio/

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