To garden is to constantly learn something new I feel. I recently flicked through some old copies of the Organic Gardener Magazine and re read an article by Peter Cundall on using biochar in the garden (Issue Mar/Apr 2015). I have also noticed that this is a product being sold by nursery and garden businesses. What struck me was the way Peter was using it to add and supply nutrients to his vegetables (in the articles case cauliflowers). The charcoal is like a sponge that can absorb moisture and fertiliser to then leach or release slowly into the soil profile and therefore to plants. The coal itself has no real nutrient value – it’s importance is in it’s ability to hold minerals and nutrients.
So, after a family hike up the hill behind our home where we discovered a very large pile of charcoal I decide to give this a go. To buy biochar is quite expensive, I figure a 30 minute work out to collect several large buckets of charcoal was a bargain! The large chucks of charcoal need to be pulverised to a finer crumble – you can do this easily enough with a block splitter dropped onto the coal in a bucket.
For this batch of biochar I was wanting to add it to the onion patch I was about to plant. So to the bucket I added worm juice, some dolomite lime and some seaweed extract. I mixed it all together and then poured over the prepared garden bed. I mixed the top part of the soil with the biochar and time will tell how the experiment goes!
Another batch I added it to the soil blocks I made for the seedlings. I was thinking this might mimic the use of slow release fertilizer.
Peter Cundall had also added compost/coco -peat, pelleted manure and some micro nutrients specifically for what he was wanting to grow (cauliflower) then added a handful to each planting hole for the cauliflowers he was growing. I feel you could create the mix you want for the different plant groups. I will continue to play with this as I have a good supply in the shed!
It is worth noting that ash from your fire place is different to the charcoal. The ash can be used in your garden as well but can be quite concentrated and alkaline. Spread it very finely over the garden or read this wonderful writers suggestions for other uses.