In article ,
"Dioclese" NONE wrote:
1491
pg. 346
Despite the charcoal, terra preta is not a by-product of slash-and-burn
agriculture. To begin with, slash-and-burn simply does not produce
enough charcoal to make terra preta in the form of carbon dioxide.
Instead, Indians apparently made terra
preta by a process that Christoph Steiner, a University of Bayreuth soil
scientist, has dubbed "slash-and-char." Instead of completely burning
organic matter to ash, ancient farmers burned it incompletely to make
charcoal, then stirred the charcoal into the soil. In addition to its
benefits to the soil, slash-and-char releases much less carbon into the
air than slash-and-burn, which has large potential implications for
climate change. Trees store vast amounts of carbon in their trunks,
branches, and leaves. When they die or people cut them down, the carbon
is usually released into the atmosphere, driving global warming.
Experiments by Makoto Ogawa of the Kansai Environmental Engineering
Center, near Kyoto, Japan, demonstrated that charcoal retains its carbon
in the soil for up to fifty thousand years. "Slash-and-char is very
clever," Ogawa told me. "Nobody in Europe or Asia that I know of ever
understood the properties of charcoal in soil."
----
"Terra preta" is an intriguing idea that could give us immediate
benefits and bequeath them to our descendants as well. Additionally, the
idea of fixing CO2 in charcoal to alleviate global warming is very
timely. It looks like it is all win/win.
--
- Billy
As you pointed out, todays' slash and burn isn't working to produce the
amount of carbon needed in the soil for biochar. I submit in former times,
this was on much smaller scale and the increased the size of such an area
over much longer time. The scale is one of the things that important when
comparing then and now.
Another point is pilings of trees and other plants for burning. Its highly
unlikely that such were made in in a large cleared centralized area as is
done now in a large scale, rather, were the tree fell instead. And such
trees weren't appreciably broken down, if at all, to facilitate burning. No
bulldozers or chainsaws for facilitate these pilings and burning. So, the
yield of carbon to the ground back then is increased much over current
practices of making major bonfires with high heat yield that consume much
more of its fuel source. This billows carbon in the form of gases much more
per amount of carbon fuel available as the older method did not burn nearly
as well or completely So, I fail to make the association of clear and burn
techniques used now compared to those methods used over a 1000 years ago.
There is no association that I can see.
--
Dave
That is the opinion I got from reading the book "1491: New Revelations
of the Americas Before Columbus"
by Charles C. Mann
http://www.amazon.com/1491-Revelatio...mbus/dp/140003
2059/ref=sr_1_1?ie=UTF8&s=books&qid=1239722303&sr=1-1
According to Mann, great areas of the Amazon basin had been terra formed
and were supporting large populations with developed orchards. Slash and
burn was a survival technique the locals used to escape their cities
which were being overwhelmed with European diseases after 1491.
--
- Billy
"For the first time in the history of the world, every human being
is now subjected to contact with dangerous chemicals, from the
moment of conception until death." - Rachel Carson
http://www.youtube.com/watch?v=WI29wVQN8Go
http://www.haaretz.com/hasen/spages/1072040.html