Bio-Char has become quite popular in recent years as we are beginning to appreciate how indigenous cultures have long used charcoal to improve impoverished soils. Our own Australian soils are notoriously low in carbon content. Bio-Char may sound mysterious but it is simply charcoal with added biology.
Charcoal can be purchased in 25-30kg sacks but it is important to ensure that it does not contain any additives which may be toxic to microbiology. It is possible to make charcoal at home and there are many videos online; but in the Australian suburbs this may upset neighbours and violate council and government regulations.
Adding the biology to your charcoal to make Bio-Char can be done in many different ways. Soaking or Mixing with any of the Microorganism Solutions described on this website will achieve some form of inoculation. The charcoal can also be soaked in the Fertilisers and Bio-Nutrients too. So get creative!
Experts advise that between 5-10% charcoal content is optimal for soil and plant health. Many Natural Gardeners have a “No-Dig” approach to their gardening and so they will apply inputs such a Bio-Char by layering material. Bio-Char has been described as a “coral reef” below the soil which provides habitat for beneficial microorganisms.
Terra Preta is much more than just Bio-Char. The legendary "Black Earth" of the Amazon, is extremely fertile and said to “magically” reproduce itself. Scientists have analysed it and Natural Farmers have attempted to replicate it. It contains Charcoal, Food Waste (including Fish Scraps), Decomposed Vegetation (Compost), Manure (most likely human), Pottery sherds, and microorganisms. One theory is that Amazonians used clay pots as toilets and waste bins and added the charcoal from their fires to absorb the smell before disposing of them. A basic modern recipe is below, but why not experiment with your own ingredients.
1 Litre Crushed Charcoal (Without Chemical Additives)
1 Litre Animal Manure (Fresh is best but not necessary)
1 Litre Compost
1 Litre Bokashi Waste (Both Liquids and Solids)
½ Cup of Fish Fertiliser
Stir into a moist mix (add some water if required) and seal in a 5 Litre Bucket. Ferment anaerobically (without oxygen) for a few months (temperature dependent). Stir the mix before leaving without the lid in a sheltered spot. The increase in oxygen will favour fungal growth and after a week or two white fungus should appear on the surface. This rich mix can then be used as a soil amendment.