I'm worried by the results that include dead or damaged plants after charcoal application. Enough of these reports in the hands of the less favourably inclined could kill terra preta nova stone dead.
Posters have shrugged them off with a "must have been because ...". I think a more scientific approach to finding out why it happened or what prevents it is needed.
Hypothesis: an addition of pure char to soil initially sucks up moisture and nutrients, making them unavailable to plants. (Don't forget:
the Amazonians didn't use anything remotely like this method).
Possible experiments:
- Drench half the char with water before application, half untreated. The water half should not then take up large amounts of dissolved nutrients from the soil.
- Drench half the char in liquid fertiliser (organic or not) before application, half untreated. Don't apply any of the leftover liquid, so that the effect is limited to what the char absorbed.
- Plots or pots of identical soil with char additions varying.
Given the long tradition in Japan of char soil amendment, perhaps there are papers from it on precise soil management regimes? What did the Japanese speakers say at Terrigal?
M
