Studies on biochar indicate potentially promising uses as a soil amendment

I am a well-read gardener living in Colfax, writing to ask your opinion of the new hot topic in gardening: biochar. For years I read that aerated compost tea was going to do wonders for food production, but when I brewed that tea, it did little or nothing to benefit my vegetable garden. Is biochar another hoax?

Answer: When it comes to both compost teas and biochar, research is still ongoing — but compost tea studies have been ongoing for decades. I don’t know how you brewed your tea so I can’t comment on your failure.

finalproductsSteven Swain, the environmental horticulture scientist for UCCE in Marin County, lets us know, “Many claims are made for compost tea, including uses as a fertilizer and as a disease suppressant. Some of these claims are realistic, others rather fanciful. As a fertilizer, aerated compost tea will quickly release large quantity of nutrients.”

But Swain points out, “Plain old compost, not the tea, typically acts to release those same nutrients in a slower manner, plus it has the added benefits of cooling and cushioning the soil. So to really get the most out of your compost, perhaps it’s best to apply it to the landscape, and let nature make the tea with rain or irrigation water, unless you have a specific need for a quick boost, and are sure you know how much to use.”

As a disease suppressant and insecticide, the compost tea research has been very inconsistent.

Swain continues, “To date, there are no peer-reviewed scientific studies that show that aerated compost tea reliably cures any disease, despite dozens of research projects aimed at investigating this over the past few decades.”

But your question specifically addressed biochar. Simply stated, biochar is the name for the charcoal created in nature after a fire.

Because oxygen is not present, there is no combustion. This charcoal obtained from the carbonization of various forms of organic matter, usually from agricultural/forestry waste, is undergoing research as a soil amendment to improve fertility and improve soil functions.

But that is not the only potential benefit to this planet. According to a study at Cornell University, “….the conversion of residues from commercial forestry and crop production to biochar could offset as much as a third of U.S. carbon emissions from fossil fuels.”

The infamous greenhouse gases could be substantially reduced. In addition, this sustainable biochar is “relatively inexpensive, widely applicable, and quickly scalable”, as emphasized by the International BioChar Initiative. In the realm of possibilities, we see biochar as a global warming game-changer, but the research is still in its infancy.

UC Davis has established a common database for all researchers to record and share their results — http://

This online resource of biochar physical and chemical characterization data does not provide recommendations for biochar use nor does it endorse any specific product.

The database exists only as resource. We can only hope that the studies quickly produce positive results.

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