Biochar

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May 072018
 

Photo © Bulleen Art & Garden

Absolutely on trend – but is it any good?

Biochar has been touted as a multi-pronged agricultural/horticultural and garden solution to improving soil fertility, lowering the need for artificial fertilisers, and a method of carbon sequestration. We are always keen to look into a safe, organic way of improving soils, thus increasing productivity. Read on for our conclusions:

Biochar is relatively new on the commercial scene (despite being used for centuries) but there are now many peer reviewed studies on its effects. The initial results are mixed but favourable and clearly further studies need to be done. Because it is a complex area with studies answering some questions but raising many more, we have done a very simple summary below.

1. Not all Biochars are created equal
a. Biochar is made by heating (200-300C) organic material in the absence of oxygen (pyrolysis). A thermochemical reaction occurs where the organic material (often referred to as biomass) is converted irreversibly to a very stable carbon-based product called biochar.
b. The properties of biochar are affected significantly by both the source of the originating organic material (biomass) and the temperatures used in pyrolysis.

2. Biochar has been shown to improve soil health and raise productivity (in a similar way to that of compost). However, the exact way this occurs is still up for debate. At this stage it appears that one pathway is in providing a favourable environment for soil microorganisms, beneficial bacteria and fungi. However more research is needed.

3. Biochar is hygroscopic. It attracts water. This ability to retain water in soils, provides dual benefits of holding water soluble nutrients within the soil profile, and keeping the moisture in the soil needed for the survival of the soil microorganisms. This characteristic of retaining water soluble nutrients means less additional fertilisers are required to maintain productivity.

4. Biochar is very stable and will remain as a component in the soil for many years.

5. There appears to be a beneficial synergy with adding both biochar and compost together to improve soil. A possible hypothesis is the combination provides both food and water for beneficial soil microorganisms, encouraging an increase in their numbers.
So overall we see no problem adding biochar to your soils or potting mix, and considerable potential benefit. It is not expensive and one application should last many years. If you feel inclined to, give it a go.

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