[Terrapreta] charcoal mix & long lasing effects

[Christoph Steiner]

Hi,
30% charcoal in Terra Preta is definitely too high! The highest carbon
values we found were around 10% which means that the charcoal
concentration can not be higher. Dr. Bruno Glaser from the University of
Bayreuth measured black carbon contents and found black carbon
concentrations in the soil organic matter of up to 35%. Therefore
estimations of a maximum of 3% charcoal are realistic and is still a huge
amount of charcoal.
Terra Preta is still exceptional fertile, but the creation date back at
least 500 years.

Best,
Christoph