[Michaelangelica]

Alfred Harris:

In Waimea, for example -- where there's hundreds of acres of what they call 'Maori soils' -- the experimental work was done on that site, and it was very clear that charcoal was mixed far further into the soil than would be expected simply from just the burning of the site.

Interviewer:

It's fascinating that two cultures so far apart should both discover the effects of charcoal in terms of agriculture. At a scientific level, how the does charcoal actually improve soil fertility?

Alfred Harris:

Okay, going back to basics: plant growth is absolutely dependent on a number of key elements -- and the major elements are nitrogen, phosphorus, and potassium. Each of those elements are highly soluble. So given a reasonable sort of rainfall, which you need for good plant growth, they'll move through the soil very quickly.

So the fertility of the soil is really dependent on the ability of that soil to retain those key elements. The soils where charcoal seems to have a particular effect -- and that's in South America, and in Japan, and here in New Zealand -- are derived from weathered volcanic ashes.

Charcoal in the Terra Preta [de Indio] soils in South America increase the fertility and maintain it over very long periods of time. It appears to have more to do with the retention of nitrogen in that situation -- but in Japan, in different types of volcanic soils, it appears the effect is actually to increase the levels of mycorrhizal fungi, which, in turn, makes the phosphate [that is] heavily bound in those soils available to plants.

Southerly: Could the Mysterious Agricultural Techniques of an Ancient Amazonian Civilization Make New Zealand Farming More Competitive? : Public Address | System

[Michaelangelica]

Just caught the last few minutes of "Time Team" on making charcoal
(BBC production
Time Team : Ironbridge/ Leighton
Time: Tuesday, September 11, 6:02 PM
Channel: ABC
Duration: 49 minutes
Rating: G
Type: Arts and Culture

A cellar in Leighton could take us back nearly 400 years. Based in a pub, it contains the remains of a blast furnace - used for making iron. What more can be discovered about the story of Leighton's lost furnace?)

Might be worth tracking down for those with a fast WWW connection.