The general consensus is that to be immediately effective, biochar needs to be charged or activated. It’s like a sponge and will absorb nutrients, microbes and fungi. Just adding freshly made biochar into the soil will actually deplete nutrients that are being sucked into the sponge giving poor results for a season.
How to Activate or Charge Biochar
There are many ways of charging biochar but here are some of the methds I’ve come across (in no particular order):
Steeping the biochar in urine for a period of weeks. This could be animal or human urine, there’s little difference. The urine starts as a sterile, nutrient rich liquid which soaks into the char and provides a feedstock for the microbes who move in later. This is one method often used in scientific studies of biochar.
Steeping in urine with added seaweed solution (such as SM3). Adding seaweed liquid or powder is frequently suggested.
Instead of urine or along with, a slurry made from cow manure or steeped sheep / horse manure is suggested by some. Some like to add poultry manure or commercially produced poultry manure pellets to the mix.
Scattering the biochar in a chicken run where it will act as a deodoriser as well as charging. Potentially the birds will eat a little but that’s not been described as a problem. It may have an effect against parasitic worms.
Worm castings mixed 50:50 with biochar plus 5% flour or molasses to feed the microbes. Mix and keep warm (20ºC) and damp (not wet) for at least 2 weeks before use.
Micronised (powdered) mineral rockdust 2 parts, 8 parts biochar, 1 part flour, 2 part worm castings. Mix and keep warm (20ºC) and damp (not wet) for at least 2 weeks before use.
Mixing 50:50 with grass clippings and leaving for 3 months to mature. Keep covered to avoid rain washing it out.
Aerobically produced compost tea is a popular charging agent. The theory is that most pathogens are anaerobic so aerobically produced compost tea is high in beneficial microbes which will drive out the pathogens.
Composting and Charging Biochar
Finally the method favoured by Tony Callaghan of Soilfixer is to add raw biochar to compost as it is being made – possibly up to 10% of the volume of the raw materials. As they compost they’ll naturally add nutrients and microbes to the char producing a humus and biochar rich compost to apply to land.
Further Information on Biochar