Gardening with biochar

Biochar is one of the most useful soil additives you can use, and while you can add it any time of year (like compost), autumn is a great time to do it before your trees go to sleep in winter, to boost the organic matter in your soil and provide more habitat to help your soil microbes survive over winter.

In the first biochar workshop we ever went to a few years ago, the presenters started by saying “Let’s clearly appreciate and understand how biochar is truly amazing and differs from fertilisers or other gardening soil additive products.”

Well, that piqued our interest, for sure. They went on to explain that one of the ways biochar is unique is that it acts on four aspects of soil at the same time:

  • physical
  • hydrological
  • chemical
  • biological

What is biochar, we hear you ask, and why should we care? Basically, biochar is just charcoal produced in a special way from plant matter and stored in the soil.

Biochar...just like charcoal
Biochar…just like charcoal

It’s brilliant for the soil and your fruit trees (we’ll tell you why in a minute), but one of the best things about it in these times of climate change is that it’s a stable, long-term way of taking CO2 out of the air, and putting it back in the soil, where it belongs. It’s not much to look, as you can see – it just looks like charcoal.

Making biochar is one of those skills (like making compost tea) that can seem a bit fiddly at the beginning, but once you know what you’re doing and you’ve got a system in place it’s a fantastic way of providing your own top-notch soil amendments, basically for free.

Learning how to make biochar at a workshop at the farm
Learning how to make biochar at a workshop at the farm

After all, it’s been produced for thousands of years (you might have heard of the amazing terra preta highly fertile soils that were created in the Amazon basin through use of biochar), well before modern technology was available, so it can’t be that complicated!

Making biochar in a milo tin
Making biochar in a milo tin

So, why is it good for fruit trees? The main benefit is that it increases soil fertility, primarily by increasing the amount of organic carbon stored in the soil.

But there’s also lots of evidence now that biochar also provides a perfect habitat for soil microbes and stimulates their activity, making your soil much more biologically active. It also improves cation exchange capacity, which is a measure of the availability of the nutrients in your soil.

You can turn ordinary biochar into “superchar” by innoculating it with things like compost tea, worm tea and microbe food, as Lann demonstrated at the workshop. This charges the biochar with both microbes and microbe food before you put it in the soil, reducing the time it takes for it to start working its magic.

But it doesn’t stop there, there’s lots of other benefits, including:

  • it improves water quality,
  • it increases retention of water in soil, and 
  • it helps nutrients stay in the soil rather than leach out.
Healthy soil with lots of organic matter and microbes
Healthy soil with lots of organic matter and microbes

If you want to find out more about the microbes that will move into the biochar “hotel” you provide by adding biochar to your soil, and exactly how vital they are to your soil health, take our Soil Biology and the Soil Food Web short course.

Thanks to John Sanderson and Lann Falconer, both Environmental Engineers for Earth Systems, for their fantastic biochar knowledge and workshops. Read our detailed blog about their workshop here.

5 thoughts on “Gardening with biochar”

  1. I’ve been making my version of biochar by pouring water on the bonfire when it’s just coals. While not as porous as traditional biochar it still does the job and is easier to make. I then inoculate it with water, sealsol, compost, worm casting and aged chook poo.

      1. True Dom, but biochar is just porous charcoal actually, and still a fantastic soil additive, and a great way to get carbon into the soil. The surface area within it for population by microbes may be less, but still super useful and fast way of relatively rapid soil improvement – and the more the better!

  2. Yes Katie I agreed. But I would say that because the fire is so big the coals in the centre near the ground are at a low temperature and sometimes not even burnt.
    While in doesn’t make biochar it’s lighter than charcoal. And you can create a lot in one go.

Leave a Reply

Your email address will not be published. Required fields are marked *