[Terrapreta] The Science of Terra Preta Formation

[Robert Klein]

the problem with rainforest soils as I have understood it is not that nutrients are not available but that they are transported by rainwater to the water table at least, leaving the surface depleted.  What is more, plant material is degraded at a very fast rate releasing that source of nutrients back to the water table.  The magic of terra preta is that it intercepts this cycle and holds nutrients at the surface available for cropping.  The most important aspect of terra preta is its powerful nutrient retention capability allowing success in adding even fish waste to the soil.  The archaeological data makes no mention of this, but I suspect that legumes were also grown heavily here besides maize and manioc.

Please read my blog postings on the making of terra preta with stone age technology to understand both the how and the natural restraints.

google arclein

----- Original Message ----
From: David Hirst .com <david at davidhirst.com>
To: Terrapreta <terrapreta at bioenergylists.org>
Sent: Tuesday, April 8, 2008 9:54:30 AM
Subject: Re: [Terrapreta] The Science of Terra Preta Formation

Jim,
It may be that there are a few nutrient recycling opportunities that are
natural, although how far they apply in the Amazon I do not know. For
example;
1.    The bodies of Salmon bring nutrients from the sea far up river, and,
after spawning, usually get caught by bears. They tend to take a few bites,
and leave the bulk of carcass in the forest, where the nutrients recycle.
The forests seem to suffer from the loss of salmon. Do any Amazon fish swim
upriver from the sea so brining up nutrients (perhaps via several food
chains)?
2.    Aeolian dust. Quote significant volumes of dust get blown about, and
land far from where they originated. In the Amazon, I guess most traces get
lost in the forest but I though Laos was build on blown dust. Some of the
dust is alive, and even scorched islands seem quite quickly to have seeds
land and germinate. Some spiders use threads to fly off and travel long
distances.
3.    Volcanoes. They are also a contributor to dust.
4.    Sulphur is also cycled from the sea as particulates (and cloud
condensation nuclei). Algae, when they get too hot tend to release DMS,
which helps form clouds (and so cools them).
5.    Tectonic movements. Upriver, there are the Andes, which are still
being pushed up, and so can carry on eroding and feeding nutrients
downstream.
Many of these are quite slow acting, but most nutrients get recycled close
to home. I understand that most rain is from evaporation within the forests.
I imagine that forest fires do occasionally occur during dry spells, and
would tend to leave some charcoal.
Most sources seem to think that TP is anthropogenic, and I am not arguing.
But natural sources cannot be entirely ruled out on nutrient cycling
grounds.
Cheers
David

David Hirst

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-----Original Message-----
From: terrapreta-bounces at bioenergylists.org
[mailto:terrapreta-bounces at bioenergylists.org] On Behalf Of Jim Joyner
Sent: 08 April 2008 16:02
To: Terrapreta
Subject: Re: [Terrapreta] The Science of Terra Preta Formation

If I might add a few things:

I find it very difficult to believe that dark earth in Amazonia had a 
natural start. Much of the muck soils in the US Midwest were due to 
catastrophic events through the ice ages. These nutrients became a 
treasure trove of nutrients that farmers are still mining. There is 
nothing comparable in the tropics that I know of. (Well, there the 
occasional guano deposits found, but even these are not soils)

There is practically no way that carbon can naturally accumulate in the 
tropics for any length of time. The one exception to that seems to be 
charcoal but that is not what we would call natural.

Also, in terms of nutrient (I'm speculating, but bear with me). For 
thousands, many hundreds of thousands of years, nutrient  has flowed 
into the Amazon from the mountains above. Some of these nutrients are 
soaked up into above ground jungle/rain forests. Some, of course, are 
bound up in aquatic life. Most are washed out to sea. But there is no 
source of nutrient in the tropics to "mine" like there are in the 
temperate zones. There is no soil deposit to mine simply because, if it 
had existed, it would  have quickly disappeared.

This means, I think, to have supported what seems to have been huge 
populations, there had to be a serious form of economizing and cycling 
of nutrient. Basically, people had to take from the rivers and some from 
the forests (so far that is gather-hunting which will not support large 
populations), but in time as they keep their waste (somehow), they 
recycled and accumulated nutrient. This recycling is not unusual (Asians 
ahve done for millenia), but it is difficult in the tropics simply 
because the medium that is necessary (for the most part) to hold these 
nutrients, in a usable way, is carbon. And most carbon under normal 
natural conditions in the tropics will will simply evaporate (actually, 
the process is burning or oxidation).

Somehow, it seems the people discovered a medium to collect, hold and 
recycle nutrients and carbon. Our guess, of course, some form of char.

Jim



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