Amazonian Dark Earth

Terra Preta de Indio ~  Terra Preta Nova

Shown at left 

Amazonian Dark Earths: Origin Properties Management

edited by J. Lehmann, et al 2003 Kluwer Academic

In 2005 an archeological documentary program introduced me to Terra Preta de Indio, translated from the Portuguese, 'Black Earth of the Indians'.  Also called Amazonian Dark Earth, this soil, produced by Pre-Columbian Amazonian Indians, remains rich and fertile today, despite being created as long as 2500 years ago. Immediately after the program I rushed to my computer and began to read as much as I could discover about this fascinating topic. The original program "The Secret of El Dorado", as produced by the BBC, is presented in full below via YouTube...

Fast forward to Spring 2008, when I enrolled in a North Carolina State University Horticulture Course, Introduction to Permaculture. For our required Research Paper and Research Project we were encouraged to choose our own topic of inquiry.  

There was no question but that I would choose Amazonian Dark Earth, Terra Preta de Indio,  as the focus for my Research Brief, (posted below).  Using what I had learned in researching my paper, creating a fully organic Terra Preta Nova, or New Age Terra Preta soil, became my Research Project. The Power Point program illustrating my Project: Replication of fully organic Amazonian Dark Earth or Terra Preta Nova is made available for interested viewers.  Click the link, box at right to run the program.  To see how our garden is growing, use the 'Garden' button on the left for photos.

A list of references for my paper, which follows, can be found by clicking here: References

Click here for a PowerPoint Presentation:  How We Replicated Organic Terra Preta Soil and Reduced Our Carbon Footprint. A .PDF version is available here.

Research Paper: Terra Preta de Indio, Amazonian Dark Earth

Donna Marie Lynk, NCSU Horticulture HS 403, April 2008

The Gift

It is becoming apparent the Pre-Columbian Amazon Indians have left the world an incredible legacy.  The soil management technique they developed creates deep, rich, humic, black soil. Their soil, Terra Preta de Indio, retains its’ fertility for centuries. Terra Preta can teach us to better feed our world, slow deforestation, minimize nutrient contamination of ground and surface water, reduce Global CO2, and create sustainable ‘non-food source’ Bio-energies (Cornell, Science Brief: 2)(Steiner, C., UNCCC Bali 2007)

 

The Discovery 

 “Somewhere, Something Incredible Is Waiting To Be Known” Carl Sagan

The lush growth of the Amazonian Rainforest belies a secret:  the natural soils, once cleared of forest, weathered by rain, sun and tropical humidity, are unsustainable for the growing of crops. Farmers continually ‘slash and burn’ new territory in a destructive cycle of ‘short crop /long-fallow shifting cultivation’ because the natural soils are exhausted in as little as two years (Lehman et al, 2003:  xv, 17).  The Amazon has been labeled a ‘Counterfeit Paradise’ by Dr. Betty J. Meggers, who contends the region incapable of sustaining the grand cities and extensive agriculture reported by the explorer Francisco de Orellana after his 1540-42 Amazon expedition.   It is only in the past few years that an international team of scientists has uncovered new evidence of those civilizations, and is making startling discoveries about how the Pre-Columbian Amerindians created Terra Preta soils, producing the world’s best soil from some of the worst (BBC Horizon) (Lehmann et al, 2003: 15, 21-22).

The Indian Soil

Terra Preta de Indio is old, dating from 500 to 2500 BP, yet these soils are still fertile today.  Farmers on one Terra Preta site have conducted intensive agriculture for forty years without the addition of fertilizer (Peterson, Neves, Heckenberger, 2001: 92 pars 3).   Terra Preta is deep, with horizons that measure up to two meters, lying in stark contrast to the yellow/white natural soils from which they are made.  Known Terra Preta deposits are vast, covering an area twice the size of Britain, an estimated 10% of the Amazon Basin, more sites may be discovered (BBC Horizon). 

  The three primary components of Amazonian Dark Earths are large quantities of Charcoal, Nutrient Material (primarily from food and plant residues), and Ceramic potshards. Fire was the essential tool for the formation of Terra Preta.  Rather than ‘slash and burn’, the Indians practiced a form of ‘slash and char’, incomplete combustion, a process called pyrolysis, to form the charcoal or Black Carbon. Pivotal to the formation of the Terra Preta, Black Carbon is found in levels 70 times higher than those of the adjacent native soils (Lehmann et al, 2003: 45, 47, 357) (Glaser et al 2001:37- 41). Black Carbon, stable in the soil for centuries, has shown to have significant impact on fertility, nutrient retention and high cation exchange levels. The increased surface area in the soils due to bio-char, may provide clues to increased nutrient cycling (Liang, et al, 2006, pars 1,4, Conclusion). Charcoal is all ‘edges’.  The charcoal acts like a coral reef for soil organisms and fungi, creating a rich micro ecosystem where organic carbon is bound to minerals to form rich soil” (Eprida, Explanation link).  Studies have documented the stability of Soil Organic Matter and significantly elevated microbial growth potential with the addition of charcoal amendments to the soil (Steiner, Zech and Teixeira, 2006) as well as increased crop production and prevention of nutrient leaching (Marris, 2006) (Eprida, Home). 

The nutrient component, what we would call ‘compost’, included a rich stew of food residues, fish bones, palm thatch, broken basket materials, plant matter, even silt from nearby rivers. Traces of human urine, turtle carapaces, animal bones, the remains of the hunt, all went into the ‘midden’ and were finally worked into the soil.  . (Lehmann et al, 2003: 40, 45).

The third pervasive ingredient of Terra Preta soil, the ceramic potshards, which are present in amounts of 10 to 25% by volume, are believed to add to the stability of the soil, provide drainage, as well as act as a nutrient and moisture sink (Lehmann et al, 2003: 46)

The Potential

The star of the Terra Preta firmament is the black carbon char, also called biochar or agrichar.  Derived from herbaceous biomass as well as trees, the char holds the key to lasting soil fertility, nutrient cycling and retention, reduced runoff, and as a carbon sink to reduce Global CO2. (Steiner, C., UNCCC Bali 2007)  Sequestering carbon is a simple effective method to reduce atmospheric CO2. 

To follow the carbon cycle lets look at a tree.  The tree pulls carbon dioxide out of the atmosphere, and locks it up in its biomass. (Lang, 2007) If the tree dies or falls over in a storm and decomposes, the carbon is released back into the atmosphere.  If the tree is burned, complete combustion releases 98% of the carbon back into the atmosphere, and you are left with ash.  If instead of burning, this same tree is pyrolysed, or turned to charcoal, the resulting black carbon can then be buried in the soil creating a stable long term carbon sink, having removed 50% of the tree carbon from the atmosphere for centuries.

 The real beauty of this system is when our tree, or biomass, is ‘charred’ the bio-energy it releases can be harnessed. Using biomass to create ‘non-food source’ sustainable energy and biochar can reduce CO2 levels by as much as 10% (Lang 2007) (Eprida, Flash, Explanation). Deforestation due to shifting slash and burn cultivation could be halted. Biomass obtained from agricultural waste, storm damage, and routine husbandry of public spaces could all be transformed into clean energy, a soil amendment that is fertile beyond our dreams, and a carbon sink that reduces the Global CO2 (Cornell, Science Brief: 2)(Eprida, Home, Flash).  The work of dedicated scientists has inspired a worldwide dialogue on Terra Preta at the World Conference on Climate Change in Bali 2007, spurring a drive to create Dr. Wim Sombroeks’ ‘Terra Preta Nova’ or New Age Terra Preta (Lehmann et al, 2003: xix).  Of keen interest is the finding that Amazonian Dark Earth may not have taken centuries to form.  Research indicates the Terra Preta formation can be rapid, if sufficient quantities of the essential components are present (Lehmann et al, 2003: 46) While the Terra Preta soils are ancient, the research is recent,  ‘40% of the papers on this subject were written in the past six years’ (Marris, 2006).  The first book on the subject, Amazonian Dark Earths (Lehmann et al) was published in 2003.

Conclusion

Rarely do we find such an elegant solution to so many of the pressing needs of our world. The promise of biochar embodies the principle of sustainability as defined by the Brundtland Commission, Meeting the needs of today’s generation without compromising the abilities of future generations to meet their own needs.” (Hooker, W. Syllabus 2008) We can all participate, on scales large and small, by incorporating char into our landscapes. (Note here that biochar tends to raise ph levels, a benefit in the acid tropic soils, but adjustments should be made accordingly)  Everyone can sequester carbon, no matter who you are or where you live. From potted plants to vegetable gardens to large-scale agribusiness.  Imagine the impact on your personal carbon footprint. What greater gift to the future can we leave than rich fertile soil and a clean environment?

Click Here To See References for the paper above.

The Challenge

 My project challenge is to create Terra Preta Nova, organically, with readily available components.  I believe so strongly in the promise of biochar, the experiment has begun.  To date approximately 450 pounds of char have been sequestered, mixed with 400 pounds of fired ceramic clay in user-friendly granular form, and rich homemade compost.    (Click here to view annotated reference document)
Photo at left:

Terra Preta Nova

Experimental bed

Eight weeks after seeds were planted.

Photo DML

 

 

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