Benefits of using Biochar in the Garden

I have a confession to make. I don’t like watering my plants every day. I’m on a constant search to find ways to spend less time watering my plants. There are many benefits of using biochar in your soil, including needing to water your plants less often.

What is biochar?

Biochar (Biological Charcoal) is a very porous high-quality form of charcoal. Biochar is made from the burning of wood at high temperatures with limited oxygen. While it can be used as a sustainable source of fuel, biochar is most known for its ability to store carbon in soil and improve soil quality.

Is biochar charcoal?

When someone uses the term biochar they are usually referring to material for an agricultural application. The term charcoal is usually used when using a wood burned material for the purpose is for heating or energy. Charcoal is made from wood, whereas biochar can be made from any natural dry material (including, but not limited to wood). As far as the actual composition of the material, they are pretty much the same thing.

Benefits of using biochar in soil

Biochar has 3 main beneficial effects on soil

Physical benefits

All woody material has natural pores in them. When the material undergoes pyrolysis to make biochar these pores remain. Lots of pours in the material translates to biochar having a large surface area. One gram of charcoal has about 9,000 square feet of surface area.

The microscopic pores in biochar form an irregular microscopic honeycomb structure. This structure improves soil aeration, water holding capacity and nutrient retention of soil. It stops the soil from becoming compacted and ensures roots can move through the soil easily. The unique structure of biochar particles helps them facilitate the exchange of nutrients and water within the soil.

Biological benefits

This structure provides a home for beneficial microbes. Beneficial microbes are essential to the healthy root systems of plants and help plants defend against pests. Whenever we add biochar to the soil we provide more surface area for these microbes to live. This leads to an increase in both the quantity and variety of microorganisms available. A healthy root system means plants can access more nutrients thus resulting in improved yield.

Chemical benefits

Biochar is a form of carbon. Carbon in soil is necessary for a process known as cation exchange. Think of the nutrients plants need (such as calcium, potassium, magnesium etc.). Many of them are (positively charged) cations. Biochar has a small charge which allows these nutrients to attach to it. When this happens, nutrients aren’t easily washed away due to heavy rains. Therefore, more nutrients are retained in the soil and thus available for plant roots.
When using synthetic fertilizers less than 10% of the fertilizer applied gets used by the plant. By adding biochar to your soil you can reduce your fertilizer expenses as more nutrients will be held by the biochar.

Biochar in acidic soils

Plant roots need a certain pH range for nutrient exchange to happen efficiently in the soil. Biochar is also very good at raising the pH of acidic soils. A study on the Effect of Biochar Amendment on Soil found that biochar was able to raise soil pH from 5.7 to 6.3. Biochar also increased the ability of the soil to exchange cations and enhanced the amount of carbon present. There was also a significant increase in bacteria, fungi and other beneficial microorganisms where the biochar was applied. Nitrogen, phosphorous and potassium were also better utilized.

How long does biochar last in soil?

Biochar doesn’t decompose, at least not in the time we would expect more organic materials to break down. Biochar can last hundreds of years. Because biochar doesn’t degrade it is a permanent improvement to the soil. Biochar is made of carbon. Because it lasts so long in the soil it prevents carbon from being released into the atmosphere. 1 ton of carbon locked away in biochar is equivalent to 3 tons of carbon dioxide permanently removed from the atmosphere

How much biochar to add to soil?

If you’re making a soil mix you shouldn’t need more than about 10% of your soil mix to be biochar. If your garden is already established you can just sprinkle the biochar on the soil surface and add your mulch on top of that. The earthworms and other critters in your soil will mix it in overtime.
A little goes a long way with biochar. 1 cubic foot of biochar is enough to apply to 350 square feet of soil. 4 tons of biochar is enough to apply to an acre of soil.

Can biochar improve crop yields?

Because of the benefits mentioned earlier, biochar can improve crop yields. However, It doesn’t happen overnight. It takes time for the microbes and nutrients to be absorbed onto the biochar’s surface. When using biochar you may notice some of the pieces in your soil going from back to white. That’s a good sign that the beneficial microorganisms are inoculating your biochar. While you may notice some benefits on yield within 6 months, that’s just the beginning. The realized benefits of crop yields from using biochar would be shown 2-3 years down the road.

How is biochar made?

Biochar is made by a process called pyrolysis. Pyrolysis is the heating up of organic material with limited oxygen. To make biochar you will need a quantity of dry organic matter and a barrel or conical hole. Fill the container with material and light the material. The goal is to provide a slow urn with limited oxygen. If the material starts turning to ash (the top will start to turn white) add more dry material to the system to reduce the supply of oxygen.
Once the material has burned sufficiently, fill the container with water. If some of the biochar floats on the surface that’s ok. Leave the container to cool overnight.

Once the system has cooled remove the biochar and discard the liquid. If the biochar pieces are too large you can crush them by hand, stomping on them with clean shoes or any other method that is convenient for you.

Why is biochar good for the environment?

Plants take in Carbon Dioxide from the air and through photosynthesis use carbon to make the structure of the plants (fruit, stems, roots, etc). Biochar is made out of carbon from plant material. Because we are taking the carbon from the air and using biochar to sequester this carbon in the soil biochar is an important solution for our current problem of excess carbon in our atmosphere. Biochar is carbon negative since it is made by removing carbon from the air and sequestering it in the soil.

Biochar and clean energy

Biochar can be used as a clean energy replacement for coal and fossil fuel. My last statement might have you wondering, “Why would it be considered clean energy? Isn’t it still sending carbon into the air when it’s burned?” Well yes, but technically that carbon was already available in circulation. It’s a better option than coal but maybe not as “clean” as wind or solar.

Final Thoughts

Biochar has many uses. Not just as an addition to soil. Biochar can also be used to manage odours from your compost bin. You can also innoculate your biochar before adding it to your soil with manure and compost tea. That way you can fertilize and add the biochar to your soil in one step. If you’re in Trinidad and would like to get your hands on some you can find it here.

Have you ever used biochar? do you have any tips you would like to share? Feel free to let us know in the comments.

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