Conservation & Environmental Matters


----- Forwarded Message
From: owen <owen@soft.co.za>
Date: Tue, 16 Jan 2007 07:09:32 +0200
To: <sawac@geasphere.co.za>
Subject: Soil Fertility through Terra Preta

Terra Preta Nova - Making terra preta at home:

Johannes Lehmann1*, Jose Pereira da Silva Jr.2, Thomas Nehls3,
Christoph Steiner3, Manoel da Silva Cravo2 and Bruno Glaser3

1 College of Agriculture and Life Sciences, Department of Crop and
Soil Sciences, Cornell University, Ithaca, NY 14853, USA; 2 Embrapa
Amazonia Ocidental, 69011-970 Manaus, Brazil; 3 Institute of Soil
Science, University of Bayreuth, 95440 Bayreuth, Germany

* corresponding author: CL273@cornell.edu

Abstract. Soil nutrient contents and availability are generally low
in the highly weathered and acid upland soils of the central Amazon.
Additionally, high precipitation and permeable soils lead to large
and rapid water percolation into the subsoil. In natural forest
ecosystems, extensive and deep root systems ensure a closed nutrient
cycling even under those high leaching conditions. In
agro-ecosystems, however, nutrient losses by leaching can be very
substantial due to usually higher nutrient loads and a less efficient
root system. The result is a low nutrient use efficiency of applied
fertilizers. Previous studies of the so-called Terra preta in the
Amazon had revealed that a main component of the organic carbon in
these soils was derived from charcoal. In a series of experiments, we
studied the management of a highly weathered Xanthic Ferralsol by
using charcoal, animal manure amendments and compost in comparison to
Terra preta soils.

In a pot experiment, total biomass production of cowpea grown on
Terra preta soil was 64% higher than when grown on a Xanthic
Ferralsol (P<0.05; N=5). Foliar P, K, Ca, Zn, Cu contents were higher
on Terra preta soils whereas Mg contents were reduced. Charcoal
amendments increased its biomass production (by 35 and 74% for 10 and
20% C amendments, respectively) and foliar nutrient contents (P, K at
high coal amendments, Cu: Mn and Mg were reduced) compared to an
unamended control and were superior to phosphate fertilization. Since
this experiment was done under conditions which did not allow
leaching of nutrients and water, the increased nutrition and biomass
production was an effect of nutrient additions by the charcoal.
Lysimeter studies indicated that solute leaching was very low in
Terra preta soils (electric conductivity in Terra preta leachate 31%
of that of Ferralsols). With charcoal amendments, leaching of applied
mineral fertilizer could be retarded but not substantially decreased.
Charcoal amendments to soil improved crop nutrition without large
nutrient losses by leaching, - the Terra preta nova.

An interesting excerpt from an enviro mag on Terra Preta in Carbon
Sequestering:

I've saved the best for last. Terra preta is new to Western science,
but it is an old technology from the Amazon that disappeared when the
native populations were wiped out by European diseases after Columbus.

The technology of black earth is simple: Instead of slashing and
burning the rainforest to make way for agriculture, long lost
Amazonian civilizations burned forest slash in smoldering piles to
make charcoal, and then buried the charcoal in the soil. This
produces an astounding increase in soil fertility. The charcoal
itself adds nutrients to soil, but it also acts as a sponge to absorb
and retain any manures or other added fertilizers for very long
periods of time. Some of the terra preta soils created more than 500
years ago are still highly fertile today.

Terra preta could be a win-win-win-win solution of tremendous
magnitude. Here's how it would work: Farmers would start by growing
biomass for energy - cornstalks, for instance. The material would be
heated with solar furnaces to make the charcoal, which releases gases
like methane. These gases can be collected and burned for energy.
Then the charcoal gets buried in the fields, making them more
productive. But the biggest prize of all is the carbon sequestration.
This is a highly effective process for pulling carbon out of the
atmosphere and putting it into long-term storage in the earth.

The best thing about this idea is that anyone can do it. My
resolution for 2007 is to try this in my own garden. But all the
voluntary efforts of individuals and even corporations won't be
enough to tackle the energy/climate crisis. We need a society-wide
mobilization of resources to develop these excellent ideas and
others, and put them into practice. My hope for 2007 is that the new
Congress will be up to it.

This is the sawac@geasphere mailing list. To Join or Leave, contact
wac@geasphere.co.za
www.geasphere.co.za