Biochar Fertilizer What You Need To Know

Biochar Organic Fertilizer

Example of 2 different biochar materials
Example of 2 different biochar materials switchgrass and hardwood

Over the past couple of decades, more people have started using biochar fertilizer as a natural way to increase their soil fertility.

I have been looking for more ways to add organic fertilization to my gardens while reducing my impact on the environment at the same time.

This is what led me to start using organic biochar fertilizer for my crops. But before I add something new, I like to find as much info about the topic as I can.

Biochar by itself does not actually act as a fertilizer if it is in its raw form. To use it as a fertilizer, we need to make sure that it has been inoculated or activated.

Using nonactivated biochar will actually draw many of the nutrients out of the soil, reducing our plant's production.

what is biochar fertilizer

Biochar is an organic fertilizer that is a safe and effective soil amendment. It reduces nutrient leaching from the soil and greenhouse gas emissions. It also provides a beneficial environment for our soil microbes.

Well, our industries are just starting to implement biochar on a large scale. This process has been around for a long time. In the Amazon, there is a soil called dark earths. These are super nutrient-rich soil resulting from Amazonian tribes burning there plant matter and reintroducing them to their dirt.

Biochar fertilizer gets created by burning biomass products like agricultural byproducts and wood in an oxygen reduced environment at high heat.

Burning these products at high heat with reduced oxygen is a process called Pyrolysis.[7]

Homemade Biochar Fertilizer

Example of pit used to burn biochar
Example Of A Pit Used To Burn Biochar

You can also make a form of biochar fertilizer at home. Now, most of us will not use an artificial oxygen reduced environment when making this at home.

Instead of using high heat and no oxygen, we can dig a shallow pit. Next, we place the organic matter into the hole burning it until the smoke begins to thin.

Once the smoke starts to thin, we will place about one inch of soil to cover the burning matter. We will let the organic matter smolder under the inch of soil until it is charred.

The dirt gets placed on top to limit the amount of oxygen feeding the fire(this is how we can easily mimic an oxygen reduced environment at our home). Once the plant matter has charred, it is time to put out the fire.

Filling watering cans and dousing where your plant matter is the easiest way to out the smoldering biochar.

Before you mix this remains into your garden, you will want to activate the biochar. Suppose we add the biochar before it is activated.

In that case, it will absorb the nutrients from the soil and reduce the plants' nutrients, so this is an essential part of creating biochar fertilizer.

If we added the biochar at this point directly to our soil before it's activated, it would start taking nutrients out of the ground around it. When this happens, it reduces the food supply that our plants need.

Biochar is devoid of beneficial naturally occurring microbes, many nutrients, and organic matter in its pure form.[8]

Activating Your Home Made Biochar Fertilizer

So what is the easiest way to activate the biochar?.

The first step is to break the chard remains down into as fine and small pieces as you can.

The most common way to activate biochar is to mix it with water and worm castings, garden compost, organic fertilizers, liquid kelp, and molasses. After a few days (2 to 3), you can now add it to your garden's soil. To get the most benefit, you may want to wait up to 10 days before adding it to the earth.

There are also commercially available concentrated nutrients and micro-organisms you can purchase to mix with your raw biochar. They are designed with naturally occurring chemicals.

Activating the biochar will allow plant-promoting root bacteria and mycorrhizal fungi to start to accumulate. These will help to transport water and nutrients to the plants.[9]

Biochar that you purchase from the store should have already gone through the activation process. This fertilizer can get used in our gardens immediately.

Different Types of Biochar Fertilizer

Many people are surprised to find out that there are quite a few different types of Biochars.

Example of different biochar
Example of different types of biochar produced

The organic matter types used to create the biochar and how it is processed can alter the final product. Using high heat quick burn or low heat with a slow burn all alter the final product's chemical properties and the pH level.

The biochar.ucdavis.eduhas created an extensive database to allow you to decide on the specific type of biochar you should get based on the particular biochar properties you need.

If you are looking to learn more about all the different ways biochar can get altered, you should check out their database.

Nutrients of different biochars
Nutrients of Different Biochars

Does Biochar Affect pH?

Biochar as a fertilizer may affect the pH of the soil. Most people have found that if you have high acidity. By adding a biochar fertilizer, it can help make the soil more alkaline.

But after I did more research, this statement is not necessarily true.

The way the biochar was processed and the plant material used can alter the final product's characteristics.[10]

Using a lower temperature when creating biochar generally produces a lower pH level. While high heat processes will result in a higher pH in the final product.

Biochar pH can range from 4.6 to 9.3, depending on the initial plant species and the production temperature.

What Is Biochar and How Diferent Biochars Can Improve Your Crops

Its not only the pH levels that can change either. But the nutrient properties can also vary depending on the organic matter and heat used to create the biochar.

Effect Of Biochar On Soil Fertility

Role Of Biochar In Soil Fertility

When people talk about soil fertility, it has to do with the soil's ability to sustain plant growth and optimize the crop yield.

Biochar, for the most part, improves the soil's physical condition. It is necessary to point out that we still lack long term field studies of all the effects of biochar in soil.

How does biochar improve soil fertility?

The porous structure that biochar consists of creates the perfect habitat for soil microbes and beneficial fungi to flourish.

Example of porous structure of biochar
Example of porous structure of biochar

Testing has shown that it increases the soil's biological community composition and microbial biomass by 125 percent.[12]

The number of nutrients that leach out from our soil will also reduce by adding biochar into the earth. Lower nutrient leaching helps to prevent fertilizers from finding their way into our groundwater.

Specifically, a significant decrease in the total amount of Nitrogen(N), Phosphorus(P), Magnesium, and Silicon(Si) leaching from the soil was seen after biochar gets added.[6]

A study from nutrient leaching on Midwestern agricultural soil showed a reduced leaching rate for total Nitrogen(N) leaching at 11 percent and Phosphorus(P) leaching by 69 percent.

Nutrient leaching is because biochar forms loose chemical bonds with soluble plant nutrients. These bonds are why the nutrients do not get washed away from rainwater and irrigation.

How do you apply biochar to the soil?

Biochar Soil Amendment

Soils that have higher amounts of sand tend to get the most benefits from biochar.

While clay soils still benefit from organic biochar fertilizer, it does not seem to provide as many benefits as sandy soil gets from it getting applied.[5]

How To Use Biochar Fertilizer

For adding biochar into the ground, we use a technique called tilling. The easiest way to till our garden is to shovel out 6 to 12 inches of soil.

Add the biochar to the broken up soil. Once you have added the biochar, you should turn over the ground several times to make sure the biochar mixes with the earth as much as possible.

There is no reason you can not use biochar with potted plants. Just mix 10 to 20 percent with your soil before filling your pots. You will still get all the same benefits as if your plants were planted into the ground.

An added benefit of using a pot is that you know your plant's root zone will stay confined to where the biochar is located.

We do not need to add biochar fertilizer every year. A single application of biochar will provide beneficial effects for several growing seasons.[11]

How Much Biochar Do I Add To The Soil?

Based on everything that I could find, the average rule of thumb is to add about 10 percent biochar to your soil.

If you have really nutrient-void soil, you can take your biochar matter up to as high as 50 percent.

In lab tests using biochar from 0 to 50 percent, results showed that biomass production was increased with rising biochar and compost amounts.[13] Adding more than 50 percent seems to start to become harmful to soil fertility.

On average, you will mix the biochar into the top 6 to maybe 12 inches of your garden. You want to make sure that the biochar is surrounding the root zone of your plants.

So if you know the depth that your plant rootzone will reach, feel free to add the biochar to that depth.

If we end up adding it lower than the root zone, our plants will not benefit from it at that point. So all the hard work you did digging and tilling served no purpose.

What Are The Pros And Cons Of Biochar

  • Benefits of Biochar (Pros)

  • 1. Improves soil quality, particularly on degraded lands.
  • 2. Increase in earthworm and mycorrhizal fungi(these are linked to plant productivity).
  • 3. It can help to increase food production and security by increasing plant yields.
  • 4. Provides the soil with better water and nutrient holding capacity.
  • 5. Helps with sequestration of carbon in the ground instead of it getting released into the air.
  • 6. Industrial biochar can help us create more renewable energy by capturing and using the pyrolysis process's heat.
  • 7. Disposal of green waste from our agriculture and forestry industry.
  • Disadvantages of Biochar (Cons)

  • 1. If the biochar is not mixed correctly in the top dressing's erosion by wind and water transport.
  • 2. Very high levels of biochar can have adverse effects on earthworm survival rates. This only seemed to happen with poultry litter biochar. [15]. Believed to be caused by pH alteration or ammonia concentration.
  • 3. Limited research has been performed on biochar and its use in different environments.
  • 4. The ability and amount of time biochar can sequester carbon in soils is still unknown, requiring further research.


Using biochar fertilizer is a great natural way for you to improve your soil fertility while helping the environment at the same time.

It helps us to keep high amounts of nutrients in our soil. It also reduces the amount of water and nutrients we need to keep applying to our gardens.

I also like knowing that I am also reducing the number of carbon emissions released into the air.

Biochar is an excellent simple step anyone with a garden can take to improve their crops and help the environment at the same time.

But to ensure we get the best plant growth from our crops, we need to use biochar combined with compost or organic fertilizer.

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