How to supercharge: biochar + nutrients + water
You will need:
• A container - eg. a bucket or wheelbarrow
• A source of nutrients - eg. compost, frass, worm castings, seaweed solution, fish emulsion, or synthetic fertiliser (or a combination)
• Time - 3 days to 2 weeks
A note on nutrients:
The ratio of biochar to nutrients will depend on the type of nutrients you're using. Adjust the type and ratio of nutrient mix to suit your plants and soil. Some examples are:
- 50% biochar, 50% compost
- 50% biochar, 25% compost, 25% worm castings
- The amounts of biochar and fertiliser appropriate for the area you will treat (i.e. 1-5L biochar per square metre, and fertiliser rate advised by the manufacturer)
- The volume of water required to cover your biochar, and the dilution of liquid nutrient mix appropriate for that volume (eg. for seaweed solution/fish emulsion, use dilution rates advised by the manufacturer).
What to do:
Add the biochar and your nutrient mix to the container, and add water to just cover it.
Give the mix a good stir, and leave for at least a few days - a week or two is great.
Apply the supercharged biochar as a wet slurry directly into planting holes, mixed with soil/potting mix, or onto the soil surface.
Notes & tips:
- You can do this mix dry, but water helps nutrients and microbes get into all the pores and pockets in the biochar’s surface
- This mix can be done on any scale - in a cup for adding to an indoor plant pot, in buckets or wheelbarrows for backyard gardens, or in troughs or tanks for market gardens and broadacre farming.
Why should I supercharge?
It’s about adding nutrients to the biochar before it goes into the soil.
Biochar is mostly inert carbon, so it isn’t a source of nutrients in itself - but it’s good at holding those nutrients (and air and water) on its surface, which is covered in microscopic pores and pockets. Think of it like a tiny, hard sponge made of carbon. It’s a soil improver, not a fertiliser.
The surface of biochar attracts molecules of nutrients - like nitrogen, phosphorous, potassium, calcium, magnesium and other trace elements - to its surface, and acts as a catalyst for the exchange of nutrients with the soil and plants. (For more detail on how that works, check out the links to Further Reading at the end of this article.)
When everything’s in balance in the soil, these nutrients are stored on the surface of the biochar in a plant-available way, through symbiotic relationships with beneficial fungi and bacteria in the soil.
When things aren’t in balance, however - for example in nutrient-poor soils or where soil life has been depleted - the few nutrients that are available can be attracted to the biochar at the expense of the plants, so we need to make sure there are enough nutrients to go around. Once the biochar is nutrient-charged, it acts as a hub for microbial activity and nutrient exchange, which makes for happy soil life and healthy plants.
Supercharging your biochar means it’s loaded with nutrients, ready and available for plants and soil life to thrive for many years to come.
Biochar in your compost is another simple and effective way to supercharge and use biochar.
As you build the layers in your compost, add biochar to make up about 5 to 20% of the total volume, or a few generous handfuls each time you add a layer or turn it.
You can add biochar at at any stage of the process, at least two weeks before using your compost. The earlier the better!
Having biochar in the mix boosts microbial action, which generates heat to extend the thermophilic (hot) stage of composting and speeds up the process. The porous surface of biochar becomes a hotbed of nutrient exchange, and retains nutrients that may otherwise be lost through leaching and off-gassing.
When it’s time to use your compost in the garden, the biochar is already there, ready to carry all those beautiful nutrients and microbes into the soil and hold them there for your plants to access.
What if I don’t have time to supercharge?
If you don’t have time to supercharge, add nutrients at the same time as adding biochar. Water in well (ideally with a liquid fertiliser mix) so the nutrients can flow and settle into the soil and biochar.
Or try our Biochar + Frass, supercharged and ready to go!
Terra Preta and co-composted biochar - Austin Liu on Medium.com
Biochar and the Mechanisms of Nutrient Retention and Exchange in the Soil - Austin Liu on Medium.com