On 06/09/2014 22:38, David Hill wrote:
On 06/09/2014 22:21, Chris Hogg wrote:
On Sat, 6 Sep 2014 19:15:09 +0200, Bigal
wrote:


About 5 years ago I read an item on the American site of garden banter
giving some of the history of biochar and its uses.

snipped

Biochar was apparently used extensively by the Amazonian Indians,
before Europeans came along.

There was a TV program about ten years ago on the Amazon rainforest,
where they reckoned that at one time it was much more densely
populated than it is now, confirming reports from one of the earliest
Spanish explorers. But no-one in recent times could believe it,
because the soil is so unproductive, and the slash-and-burn methods
currently practiced only gives a couple of years of useful agriculture
before the soil is exhausted, which means it cannot support a large
population.

However, they'd discovered that three or four centuries ago, they used
to cultivate areas of soil enriched with charcoal (they didn't say how
it got there, whether from natural burning or man-made fires), and
this greatly improved the fertility of the soil and sustained a much
greater number of inhabitants. They call this soil Terra Preta. Sadly,
with the arrival of European diseases, this large indigenous
population mostly died out to the level it is today.

See also http://en.wikipedia.org/wiki/Terra_preta


Never tried it. How does it differ from just adding lots of BBQ
charcoal?

I thought that all charcoal was Bio.
Many years ago when we lived outside Hastings we had a friend who was a
charcoal burner and we used to get sacks of charcoal dust and spread
that on our heavy clay soil.
It helped to make the soil easier to work, and certainly did no harm.

Woodash is great for fruit trees and shrubs that like high potash and
any left over charcoal helps the drainage on things like onion beds.
Allegedly it helps keep bulb fibre sweet although I remain unconvinced.

Biochar is just a fancy US name for wood charcoal.

--
Regards,
Martin Brown