Charcoal in Secrets to Great Soil: A Grower's Guide to Composting, Mulching, and Creating Healthy, Fertile Soil for Your Garden

Secrets to Great Soil: A Grower's Guide to Composting, Mulching, and Creating Healthy, Fertile Soil for Your Garden and Lawn (Storey's Gardening Skills Illustrated)
Elizabeth P. Stell in tdc's Farmgate

Charcoal used as an aggregate keeps soils 'sweet', and has value somewhere between bark and lava rock. It is used as a base layer in planters and as a filter media. Charcoal is also used to contain chemical spills and thus may capture nutrients and pesticides used in plant cultures. The ability of plants to recapture these elements and in what form is unknown to this author. However, charcoal has proven to be an excellent aggregate in epiphytic culture and a good substrate in planting beds.