In article ,
"Nancy Young" wrote:

FarmI wrote:
"Nancy Young" wrote

I keep hearing good things about biochar as a soil amendment.

Does anyone here have experience using it? I'm thinking of
adding it to my flower gardens and vegetable beds.

In addition to the things that Billy has said, in the 'old days' when
wood burning fires were still common, the seived charcoal was used in
Spring to spread in an area where the soil needed warming. Being
black it worked to warm the soil and so give gardeners a bit of a
jump on the season.

That's really interesting, this is the first I've been reading about the
'dark earth' thing. I just heard about biochar last year, I guess it
just never came up in all the gardening stuff I've read or watched.
Thanks.

nancy



"1491: New Revelations of the Americas Before Columbus"
by Charles C. Mann
http://www.amazon.com/1491-Revelatio...umbus/dp/14000
32059/ref=sr_1_1?s=books&ie=UTF8&qid=1296839060&sr=1-1
(available from better libraries near you)

p.344
GIFT FROM THE PAST
"Landscape," in this case, is meant exactly‹Amazonian Indians literally
created the ground beneath their feet. According to Susanna Hecht, a
geographer at the University of California at Los Angeles, researchers
into upland Amazonia took most of their soil samples along the region's
highways, which indeed passed through areas with awful soil‹some regions
were so saturated with toxic aluminum that they are now being mined for
bauxite. A few scientists, though, found patches of something better.
"In part because of the empty-Amazon model," Hecht told me, these were
"seen as anomalous and insignificant." But in the 1990s researchers
began studying these unusual regions of terra preta do Índio‹rich,
fertile "Indian dark earth" that anthropologists believe was made by
human beings.

Throughout Amazonia, farmers prize terra preta for its great
productivity; some have worked it for years with minimal fertilization.
Among them are the owners of the papaya orchard I visited, who have
happily grown crops on their terra, preta for two decades. More
surprising still, the ceramics in the farm's terra preta indicate that
the soil has retained its nutrients for as much as a millennium. On a
local level, terra preta is valuable enough for locals to dig it up and
sell as potting soil, an activity that, alas, has already destroyed
countless arti-facts. To the consternation of archaeologists, long
planters full of ancient terra preta, complete with pre-Columbian
potsherds, greet vistors to the Santarem airport. Because terra preta is
subject to the same punishing conditions as the surrounding bad soils,
"its existence is very surprising," according to Bruno Glaser, a chemist
at the Institute of Soil Science and Soil Geography at the University of
Bayreuth, Germany. "If you read the textbooks, it shouldn't be there."*


*Terra preta exists in two forms: terra preta itself, a black soil thick
with pottery, and terra mulata, a lighter dark brown soil with much less
pottery. A number of researchers believe that although Indians made
both, they deliberately created only the terra mulata. Terra preta was
the soil created directly around homes by charcoal kitchen fires and
organic refuse of various types. I use terra preta loosely to cover both.

Because careful surveys of Amazon soils have never been taken, nobody
knows the amount and distribution of terra preta. Woods has guessed that
terra preta might represent as much as 10 percent of the Amazon basin,
an area the size of France. A recent, much more conservative estimate is
that it covers .1 to .3 percent of the basin, a few thousand square
miles. The big difference between these numbers matters less than one
might expect: a few thousand square miles of farmland was enough to feed
the millions in the Maya heartland.
Most big terra preta sites are on low bluffs at the edge of the
flood-plain. Typically, they cover five to fifteen acres, but some
encompass seven hundred or more. The layer of black soil is generally
one to two feet deep but can reach more than six feet. According to a
recent study led by Dirse Kern, of the Museu Goeldi in Belem, terra
preta is "not associated with a particular parent soil type or
environmental condition," suggesting that it was not produced by natural
processes. Another clue to its human origin is the broken ceramics with
which it is usually mixed. "They practiced agriculture here for
centuries," Glaser told me. "But instead of destroying the soil, they
improved it, and that is something we don't know how to do today" in
tropical soils.
As a rule, terra preta has more "plant-available" phosphorus, calcium,
sulfur, and nitrogen than is common in the rain forest; it also has much
more organic matter, better retains moisture and nutrients, and is not
rapidly exhausted by agricultural use when managed well. The key to
terra preta's long-term fertility, Glaser says, is charcoal: terra preta
contains up to sixty-four times more of it than surrounding red earth.
Organic matter "sticks" to charcoal, rather than being washed away or
attaching to other, nonavailable compounds. "Over time, it

p.346

partly oxidizes, which keeps providing sites for nutrients to bind to."
But simply mixing charcoal into the ground is not enough to create terra
preta. Because charcoal contains few nutrients, Glaser argued,
"high-nutrient inputs‹excrement and waste such as turtle, fish, and
animal bones‹are necessary." Special soil microorganisms are also likely
to play a role in its persistent fertility, in the view of Janice Thies,
a soil ecologist who is part of a Cornell University team studying terra
preta. "There are indications that microbial biomass is higher in terra
preta than in other forest soils," she told me, which raises the
possibility that scientists might be able to create a "package" of
charcoal, nutrients, and microfauna that could be used to transform bad
tropical soil into terra preta.

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‹the carbon mostly goes into the air
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."

Indians are still making terra preta in this way, according to Hecht,
the UCLA geographer. Hecht spent years with the Kayapo, in central
Amazonia, watching them create "low-biomass" fires "cool enough to walk
through" of pulled-up weeds, cooking waste, crop debris, palm fronds,
and termite mounds. Burning, she wrote, is constant:
"To live among the Kayapo is to live in a place where parts of the
landscape smolder." Hecht regards Indian fire as an essential part of
the Amazonian landscape, as it was in the forests of eastern North
America. "We've got to get over this whole Bambi syndrome," she told me,
referring to the movie's forest-fire scene, which has taught generations
of children that burning wildlands is evil. "Let the Kayapo burn the
rainforest‹they know what they're doing."

In a preliminary test run at creating terra preta, Steiner, Wenceslau
Teixeira of the Brazilian Agricultural Research Enterprise, and Wol-fang
Zech of the University of Bayreuth applied a variety of treatments
involving charcoal and fertilizers for three years to rice and sorghum
plots outside Manaus. In the first year, there was little difference
among the treatments (except for the control plots, in which almost
nothing grew). By the second year, Steiner said, "the charcoal was
really making a difference." Plots with charcoal alone grew little, but
those treated with a combination of charcoal and fertilizer yielded as
much as 880 percent more than plots with fertilizer alone. His "terra
preta" was this productive, Steiner told me, despite making no attempt
to re-create the ancient microbial balance.
--
- Billy
"When you give food to the poor, they call you a saint. When you ask why the poor have no food, they call you a communist."
-Archbishop Helder Camara
http://peace.mennolink.org/articles/...acegroups.html
http://english.aljazeera.net/indepth...130964689.html