How to Sterilize Soil Without Baking: A Step-By-Step Guide


Sterilizing soil is all about purifying it of pests and other threats that could lead to issues with growing plants, but there are ways to do it other than baking?

What are the non-baking methods of sterilizing soil? Soil sterilization methods can be divided into two categories, namely the chemical treatment and heat treatment. Both come with their own pros and cons, as well as have various. In the case of the heating method, using the power of the sun is one while in the chemical department, the use of several compounds is common.

Soil sterilization is a rather novel approach to making use of soil that would have otherwise been unusable, but it does come at a price that you need to be wary of.

Methods for Soil Sterilization

There are several methods involved in sterilizing the soil and each of them can be quite the doozy to handle. They all present you with a certain level of risk and they do require you to be a bit more present when it comes to actually you paying attention to the details. With that said, the two main categories involved in sterilizing soil are:

·         Chemical treatment

·         Heat treatment

One is done a lot more commonly than the other and there can be quite a few differences when you are talking about scale. What’s more, there is also the question of function since you will need to also consider why you are doing the soil sterilization, in the first place. There are major differences in the methods that will be open to you if you are planning on having plants or not.

With that said, let’s take a look at the various solutions available to you in the table below. Naturally, since we will not be considering baking, the use of the oven will not be included in the list. However, a microwave oven is not the same, which is why it will be in the table below:

MethodDetails
Industrial ChemicalsThere are chemicals that are used on a wide scale and are only really done by commercial enterprises due to the costs involved, and they make use of special compounds for soil sterilization
BleachFor smaller jobs, bleach can be used to kill insects, fungus, and pretty much any harmful organism in soil, but this largely makes the soil unusable for growing plants
Hydrogen PeroxideUnlike with bleach, hydrogen peroxide can leave the soil still able to support life, but this will involve much smaller projects like potted plants
SolarThis is a method for heating the soil using the power of the sun, a clear plastic wrap, and quite a bit of ingenuity on your part as a gardener
SteamBelieve it or not, you can actually sterilize soil in a pressure cooker, but this will obviously be confined to only small amounts of dirt
MicrowaveAs is the case with the steam option, a small amount of soil can be placed inside a microwave where everything living in the dirt will be obliterated thanks to the radiation from the device

As you can see, some of these options might not be viable for you to use simply because they are either more than you really need or are just not suitable for your goals. Either way, you need to make up your mind as to which of them will be used for your particular needs.

Industrial Chemicals – There are a ton of different examples of industrial chemicals that are used for wide-scale soil sterilization. Different companies use different compounds and the mixture of those substances will determine their effectiveness. What’s more, depending on what compounds are used and how the soil can either be left useful for planting or not.

Whatever the case may be, if you are not dealing with soil that is several hectares in size, you shouldn’t have to worry about this particular option. As already said, only large scale projects really make use of this particular method. More than anything else, you would have to worry about such things as the costs and the manpower, not to mention the time.

So, if we actually look at this from a practical point of view, it would be no exaggeration to say that you would literally be better off choosing any other option other than this. After all, it might actually be cheaper to replace all of the soil in your small property than to use this particular method. At least then, you will be sure that you have finally achieved true cleanliness.

Bleach – Next is bleach, which is probably the most accessible chemical on this list that will not leave you hurting once the bill is due. This is a fairly accessible substance and once you pour it all over the soil that you want to sterilize, it should be easy enough for you to see some results. You’ll find that this is actually an excellent way to get the job done if your only goal is sterilization.

As already mentioned, though, if you intend to grow plants on the soil that you just sterilized, you had better not use this method. Even when diluted, the mere presence of bleach would be equivalent to salting the earth. You won’t see anything grow after you have treated the soil with this substance, with even the most stubborn weeds simply withering away.

If you are still intent on using this method, though, you might want to make sure that you don’t use pure bleach. You need to dilute it with a 1:1 ratio of the chemical and water. This is not only meant to reduce the potency of the bleach, which can be quite over the top, it will also help to extend your use of the substance.

Hydrogen Peroxide – Aside from bleach, the good old hydrogen peroxide is another chemical that you can turn to for sterilizing unclean soil. However, unlike the notorious substance used for cleaning crime scenes, hydrogen peroxide can actually leave the soil in a state where it is still fit to support plant life. What’s more, even if you use it on soil with plants, it will be just fine.

This is a good option for those who might be thinking about just using a chemical for cleaning their soil without having to go through a lot of hoops while still being able to grow stuff. It presents you with the best outcomes from both worlds. However, you do need to think about the costs.

While hydrogen peroxide is cheap on its own, if you need a ton of it for a wide area of infected soil, the costs could stack up. Even when you dilute the substance with water to double its volume, you will still be facing quite a bit of expense. This is why such an option is best done on a small scale. A single pot of soil should not prove too much for using this kind of option.

Solar – Then we have the solar option, which basically makes use of the power of the soon to cook the soil that you are trying to cleanse. You do this by cordoning off the patch of soil that you are trying to sterilize. You will then need to churn it and then remove any debris that might pose an obstacle later for when you need to apply the plastic sheet.

Once that is done, you will then need to lay the plastic sheet over the area that you are trying to cleanse and then allow the heat of the sun to do the job for you. It is important to note that size will be a factor here. If the amount of soil you are trying to cleanse is small enough, you can actually just put it in a plastic bag and let it sit under the sun.

Whatever the case may be, this process will take quite a long time to finish. This is a project that can last about four to six weeks, so you definitely want to make sure to take some time to prepare for it. You will also need to time this project during the hottest period of the year so that you can make the most of the sun’s rays during that time.

Steam – Next, we have the option of steam, which can be a bit tricky compared to the methods that we have discussed, so far. This is because we will be making use of cooking implements in order to get the job done. The most effective solution here is simply making use of a pressure cooker, which is saying something considering that you will be placing dirt inside it.

For anyone who is cringing at the thought of using a pressure cooker for sterilizing soil right about now, this is actually a fairly common method. Obviously, you should not use the pressure cooker that you prepare your food with. It can either be an old one that you have on hand or you just buy one from a garage sale or something.

Either way, the process is pretty much a simple matter. You place the soil in a container that won’t be damaged by heat and place it in the pressure cooker. You then turn the heat on, allow the steam to build up and then allow the heat to kill the organisms in the soil for up to 30 minutes. Do make sure that you don’t forget you are doing this, though, since you could be looking at a disaster, otherwise.

Microwave – Finally, we have the option of using a microwave, which is another option that a lot of folks might not want to think about. After all, why would you waste a perfectly good microwave for heating dirt? Regardless of whether or not you choose to use this option in the end, the important point is that you know about it.

The process is fairly straightforward, as well. You place the soil in a container that can be microwaved and make sure that there are no metals mixed in. It cannot be emphasized enough that it would be disastrous if there was any steel, bronze, or copper in the mix when you turn the microwave on.

Once you have your soil ready, you will then want to set the microwave’s power on the highest setting. You will set the time for about five minutes at a time. There is no set figure here since a lot of this will actually depend on the power of your microwave.

Why Sterilize the Soil?

On the matter of sterilizing the soil that you are going to use, what exactly are the reasons for doing so? Why would you go through all the trouble to cleanse dirt to the point where you would actually risk your health? Well, if you actually want your plants to grow healthy and strong, you will just have to do this without really thinking too much about it.

To start with, any kind of soil that comes from any source comes with the risk of having pests, diseases, infectious organisms, and the like. It does not matter if you get it from a store or direct from the origins, it is all the same. With this being the case, sterilizing the soil can basically be considered as a safety precaution against those things.

The cleansing methods that were mentioned here will basically help you get rid of bugs, fungus, diseases, and other nasty stuff that has settled in the soil. You never really know what kind of infection can surface from dirt that was dug up from who knows where. Sterilizing that clump of dirt is simply the best way for you to make sure that it is absolutely safe to use.

Which Method is for You?

With all of that said, you might now be wondering which method you should choose for your particular case. If we are going to be blunt about it, though, you cannot realistically expect that all of these options are viable to you. So, how do you decide which method you should choose for your particular circumstance? Well, you can start by looking at the compatibility.

For example, if you only need to clean the land of bugs, infections, and diseases so that you can build stuff on it without worrying, then you can go with using bleach. This way, you won’t have to worry about things like your potted plants that you will place on top of the soil becoming sick or infected.

If you don’t really want to get through too much effort to cleanse the soil that already has a plant growing out of it, you can also turn to hydrogen peroxide. You won’t really have to make special preparations and your plant will come out of the treatment unscathed.

Then again, if you really want to make sure that the soil will be cleansed by the time you use it, there should be no issue in using any of the other heat treatments. Just be ready to put in a lot of time and effort.

Related Question

How Do You Kill Bugs in Potting Soil?

Bugs in potting soil can be killed in any number of ways, including the use of chemicals like hydrogen peroxide. Just be careful and do your homework before you do so, however, since you want to make sure that the soil will actually be able to support life afterward. Using pesticides works too.

Can You Use Bleach to Sterilize Soil?

As already mentioned earlier, bleach can be used to sterilize soil but it will end up completely ruining it for all time. Nothing will ever grow from that patch of earth for all time, so you need to understand the consequences of using bleach for sterilizing the soil if you are thinking of doing it.

When to Sterilize the Soil

On the topic of sterilizing the soil, how do you know when it is time to sterilize the patch of earth that you are looking at? When do you decide to go with the drastic measure of using chemicals and heat to cleanse soil? Well, this would depend on a few things, namely just how neurotic you can be and how bad the problem is.

In the first scenario, there are some people who just can’t help but feel a little bit paranoid about the prospect of planting their precious flowers, vegetables, and other ornamental greens. This goes doubly true when the soil that they will be planting on is not familiar to them. With that being the case. It only makes sense that they would want to turn to sterilization.

On the other hand, there is also the very real possibility that the soil that you might plant on is infested with all kinds of nasty bugs and fungi. If the previous batch of plants that were buried in the soil died due to these factors, you have no choice but to sterilize that soil.

When to Give Up on Soil

It should be noted, though, that no matter how much you may want to save a patch of dirt, there are just times when you have to give up on the soil that you are considering. This includes the point where there is just too high of a risk of an infection happening when everything you planted there died as a result. At that point, there is no helping the soil since it is already long gone.

Then there are soils that already went through a sterilization process and have since become quite damaged. Even though most people don’t think about it all that often, patches of the earth does have a limit and can also go through a version of death. When that happens, another round of cleansing would no longer be worth doing.

Finally, if it would be a lot cheaper to just replace the soil that is already full of sickness and infestation than it is to sterilize it, you really have no reason not to do so. It would be the best option for you since it saves you money and helps you avoid stress. 

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