Gardening With Biochar


Shan MacPherson

Put simply, the why is because biochar improves soil fertility, structure, oxygen and water retention, and reduces compaction.

Shan with a 35-pound kohlrabi

Biochar is adored by microbes. If you mulch with biochar that hasn’t been inoculated beforehand, these charming life forms will climb up and reside in these new-to-them mansions, reducing the fertility of the soil they just left. So inoculate first, and more and more microbes will inhabit this particular paradise.

You can inoculate your biochar with urine, with grass clippings, animal poop or in your compost pile. Take your pick. A week or two in a pile of grass clippings should be sufficient.

The surface area of a gram of biochar is reputed to be about that of a soccer pitch. Not something I’ve ever tested, but it sure is impressive.

Biochar is negatively charged. This means that positively charged elements, such as calcium and potassium, attach to it. Plant roots will take what they need from the biochar by offering up the appropriate number of hydrogen atoms to match the number of electrons on the element they’re seeking.

This is called cation exchange and doesn’t work for phosphorus because that’s positively charged. However, arbuscular mycorrhizae like the protection biochar gives them from nematodes and are a brilliant system of phosphorus delivery, among other things.

Biochar comes out of the kiln with lumps both large and small and anything in between. For the tilth of the soil and the amount of surface area presented, small is desirable, such as the size of an ice cube on down. My neighbor made me a pounder, a thick piece of wood on the end of a handle. It works well.

Do not breathe in biochar dust. Wear a mask when you’re handling it dry. Coating your lungs with microbial heaven can only lead to trouble.

Biochar Composting Tutorial by Rick Laing

Rick also has biochar for sale. Contact him at: