FOR THE GARDEN CONNOISSEUR

In this week’s article I want to focus on two very important aspects of biochar that can kick you in the face if not knowing about it, because biochar is not biochar, is not biochar.

It is firstly very important to understand that different feed stocks result in different char structures and –qualities. Unfortunately, it is very difficult to know the char quality when buying a biochar product. Maybe, the best that I can recommend here is to know who you are buying from.

Over the years I received many different chars from many different people. It ranged from recycled car tyres made into char to coal dust presented as biochar. Even normal, good quality charcoal is not necessary good quality biochar that can be used as a soil amendment. I’m performing two practical tests when receiving a char sample: 1. Put the pure char in water and evaluate the reaction. If it absorbs water without shaking and stirring, it indicates a low volatile content – positive. 2. I do a lettuce germination test in the pure char. If germination is normal, it indicates the absence of toxins that can hinder normal plant growth. When these two quality tests give positive results, the next step is to analyse the carbon content of the biochar.

This brings me to the second important aspect of biochar quality, the manufacturing process. As was mentioned before, the manufacturing process of biochar is called pyrolysis and is performed in an oxygen restricted environment. In layman’s terms it means that biomass gets heated up to a temperature where combustion takes place. The biomass is kept in the environment until all volatiles are burned off. The quality of the process also determines the ash content in the final product. Low ash content normally represents a better char.
Wood is the main source for biochar production. There are however many different types of wood that all result in different carbon structures which is a topic for another day.

Enough of the technical stuff, IT IS OFFICIALLY SPRING. And spring means growing. To optimize growth and production of your plants, don’t forget to create a healthy environment in which roots can utilise all available nutrients.

Hennie du Plessis (083 787 0432)
Agriculturist

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