Q&A

DEAR NEW FARM:

I read Paul Hepperly’s article on Pre-Columbian charcoal soils while researching a lecture on urban soils I will deliver this month in Singapore. Do you have any findings on the amount of charcoal that should be added to the soil or the particle size? I have found that Shell is marketing charcoal in Malaysia for horticultural applications, and I am attempting to find out their practices and recommendations. Are you aware of anyone using charcoal in temperate soils?

My work is in urban soils. I often design soil systems that are placed under sidewalks where there is no ability to add fertilizer or compost after the completion of the construction. Do you think that charcoal might have an application in this situation? If so, at what rate might you want to add charcoal to the soil?

Are you aware of any environmental impacts from charcoal production? Is commercial charcoal produced from scrap and waste wood?

Sincerely,
James Urban
FASLA

 

Dr. Paul resonds:

DEAR JAMES:

My family name on my mother's side is Urban, so we are probably related!

Horticultural charcoal is used as de-toxicant especially in sensitive orchid culture. For this purpose, only small amounts are needed. Some pilot plants get hydrogen from biomass, leaving char as an amendment. This would be the most benign way of charging soil with char carbon (see the www.eprida.com website).

There is relatively little on the rates of charcoal that would help as a soil amendment, but in studies on Indian Black soils they were using it at about 10 percent by weight to test its effects with good results.

Good luck with your talk,
PAUL

 

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