Terra preta

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Left - a nutrient-poor oxisol; right - an oxisol transformed into fertile terra preta

Terra preta (Portuguese pronunciation: [ˈtɛʁɐ ˈpɾetɐ], locally [ˈtɛhɐ ˈpɾetɐ], literally "black earth" or "black land" in Portuguese) is a type of very dark, fertile anthropogenic soil found in the Amazon Basin. Terra preta owes its name to its very high charcoal content, and was made by adding a mixture of charcoal, bone, and manure to the otherwise relatively infertile Amazonian soil. It is very stable and remains in the soil for thousands of years.[1] It is also known as "Amazonian dark earth" or "Indian black earth". In Portuguese its full name is terra preta do índio or terra preta de índio ("black earth of the Indian", "Indians' black earth"). Terra mulata ("mulatto earth") is lighter or brownish in colour.[2]

Terra preta is characterized by the presence of low-temperature charcoal in high concentrations; of high quantities of pottery sherds; of organic matter such as plant residues, animal feces, fish and animal bones and other material; and of nutrients such as nitrogen (N), phosphorus (P), calcium (Ca), zinc (Zn), manganese (Mn).[3] It also shows high levels of microorganic activities and other specific characteristics within its particular ecosystem. It is less prone to nutrient leaching, which is a major problem in most rain forests. Terra preta zones are generally surrounded by terra comum ([ˈtɛhɐ koˈmũ] or [ˈtɛhɐ kuˈmũ]), or "common soil"; these are infertile soils, mainly acrisols,[3] but also ferralsols and arenosols.[4]

Terra preta soils are of pre-Columbian nature and were created by humans between 450 BC and AD 950.[5][6] The soil's depth can reach 2 meters (6.6 ft). Thousands of years after its creation it has been reported to regenerate itself at the rate of 1 centimeter (0.39 in) per year[7] by the local farmers and caboclos in Brazil's Amazonian basin, who seek it for use and for sale as valuable compost.

History[edit]

Early theories[edit]

The origins of the Amazonian dark earths were not immediately clear. One idea was that they resulted from ashfall from volcanoes in the Andes, since they occur more frequently on the brows of higher terraces. Another theory considered its formation to be a result of sedimentation in tertiary lakes or in recent ponds.

Anthropogenic roots[edit]

Because of their elevated charcoal content and the common presence of pottery remains, it is now widely accepted that these soils accreted near living quarters as residues from food preparation, cooking fires, animal and fish bones, broken pottery, etc., accumulated. The intentionality of the formation of terra preta has not been demonstrated, rather it is believed to have formed under kitchen middens. Areas used for growing crops around living areas are referred to as terra mulata. Terra mulata soils are more fertile than surrounding soils but less fertile than terra preta, and were most likely intentionally improved using charcoal.

This type of soil appeared between 450 BC and AD 950 at sites throughout the Amazon Basin.[6]

Pre-Columbian Amazonia[edit]

The Spanish explorer Francisco de Orellana, the 16th century explorer who was the first European to traverse the Amazon River, reported densely populated regions running hundreds of kilometers along the river, suggesting population levels exceeding even those of today. These populations left no lasting monuments, possibly because they used local wood as their construction material, which would have rotted in the humid climate (stone was unavailable). While it is possible Orellana may have exaggerated the level of development among the Amazonians, their semi-nomadic descendants have the odd distinction among tribal indigenous societies of a hereditary, yet landless, aristocracy, a historical anomaly for a society without a sedentary, agrarian culture. This suggests they once were more settled and agrarian but became nomadic after the demographic collapse of the 16th and 17th century, due to European-introduced diseases, while still maintaining certain traditions. Moreover, many indigenous people adapted to a more mobile lifestyle in order to escape colonialism. This might have made the benefits of terra preta, such as its self-renewing capacity, less attractive—farmers would not have been able to employ the renewed soil as they migrated for safety. Slash-and-char might have been an adaptation to these conditions.

The BBC's Unnatural Histories presents evidence that Orellana, rather than exaggerating his claims as previously thought, was correct in his observations that an advanced civilization was flourishing along the Amazon in the 1540s. It is believed that the civilization was later devastated by the spread of diseases from Europe, such as smallpox.[8] The evidence to support this claim comes from the discovery of numerous geoglyphs dating between 0–1250 AD and terra preta.[9]

For 350 years after the European arrival by Vicente Yáñez Pinzón, the Portuguese portion of the basin remained an untended former food gathering and planned agricultural landscape occupied by those who survived the epidemics. There is ample evidence for complex large-scale, pre-Columbian social formations, including chiefdoms, in many areas of Amazonia (particularly the inter-fluvial regions) and even large towns and cities.[10] For instance the pre-Columbian culture on the island of Marajó may have developed social stratification and supported a population of 100,000 people.[11] Amazonians may have used terra preta to make the land suitable for the large scale agriculture needed to support large populations and complex social formations such as chiefdoms.[11]

Location[edit]

Terra preta soils are found mainly in Brazilian Amazonia, where Sombroek et al.[12] estimate that they cover at least 0.1 to 0.3%, or 6,300 to 18,900 square kilometres (2,400 to 7,300 sq mi) of low forested Amazonia[2]); but others estimate this surface at 10.0% or more (twice the area of Great Britain).[7][13]

Plots of terra preta exist in small plots averaging 20 hectares (49 acres), but areas of almost 900 acres (360 ha) have also been reported. They are found among various climatic, geological, and topographical situations.[2] Their distributions either follow main water courses, from East Amazonia to the central basin,[14] or are located on interfluvial sites (mainly of circular or lenticular shape) and of a smaller size averaging some 1.4 hectares (3.5 acres), see also distribution map of terra preta sites in Amazon basin.[15] The spreads of tropical forest between the savannas could be mainly anthropogenic — a notion with dramatic implications worldwide for agriculture and conservation.[16]

Terra preta sites are also known in Ecuador, Peru, French Guiana,[17] in Benin, Liberia, and on the South African savannas.[3] Similar dark earth was found in late Roman Britain.

Pedology[edit]

Terra preta is defined as a type of latosol, having a carbon content ranging from high to very high (more than 13–14% organic matter) in its A horizon, but without hydromorphic characteristics.[18] Terra preta presents important variants. For instance, gardens close to dwellings received more nutrients than fields farther away.[19] The variations in Amazonian dark earths prevent clearly determining whether all of them were intentionally created for soil improvement or whether the lightest variants are a by-product of habitation. The varied features of the dark earths throughout the Amazon Basin suggest the existence of an extensive ancient native civilization dating back 500 to 2500 years.

Terra preta's capacity to increase its own volume—thus to sequester more carbon—was first documented by pedologist William I. Woods of the University of Kansas.[7] This remains the central mystery of terra preta.

The processes responsible for the formation of terra preta soils are:[4]

  1. Incorporation of wood charcoal
  2. Incorporation of organic matter and of nutrients
  3. Role of micro-organisms and animals in the soil

Wood charcoal[edit]

The transformation of biomass into charcoal produces a series of charcoal derivatives known as pyrogenic or black carbon, the composition of which varies from lightly charred organic matter, to soot particles rich in graphite formed by recomposition of free radicals.[20] Here, all types of charbonized materials are called charcoal. By convention, charcoal is considered to be any natural organic matter transformed thermally or by a dehydration reaction with an Oxygen/Carbon (O/C) ratio less than 60[20] smaller values have been suggested.[21] Because of possible interactions with minerals and organic matter from the soil, it is almost impossible to identify charcoal with any certainty by determining only the proportion of O/C. The Hydrogen/Carbon percentage[22] or molecular markers such as benzenepolycarboxylic acid,[23] are therefore used as a second level of identification.[4]

The indigenous people added low temperature charcoal to poor soils. Up to 9% black carbon has been measured in some terra preta (against 0.5% in surrounding soils).[24] Other measurements found carbon levels 70 times greater than in surrounding Ferralsols,[4] with approximative average values of 50 Mg/ha/m.[25]

The chemical structure of charcoal in terra preta soils is characterized by poly-condensed aromatic groups, that provide prolonged biological and chemical stability against microbial degradation; it also provides, after partial oxidation, the highest nutrient retention.[4][25] Low temperature charcoal (but not that from grasses or high cellulose materials) has an internal layer of biological petroleum condensates that the bacteria consume, and is similar to cellulose in its effects on microbial growth.[26] Charring at high temperature loses that layer and brings little increase in soil fertility.[7] The formation of condensed aromatic structures depends on the method of manufacture of charcoal.[23][27][28] The slow oxidation of charcoal creates carboxylic groups; these increase the cations' exchange capacity of the soil.[29][30] The nucleus of black carbon particles produced by the biomass remains aromatic even after thousands of years and presents the spectral characteristics of fresh charcoal. Around that nucleus and on the surface of the black carbon particles, there are higher proportions of forms of carboxylic and phenolic carbons spatially and structurally distinct from the particle's nucleus. Analysis of the groups of molecules provides evidences both for the oxidation of the black carbon particle itself, as well as for the adsorption of non-black carbon.[31]

This charcoal is thus decisive for the sustainability of terra preta.[29][32] Soil amendment to ferralsol with wood charcoal greatly increases productivity.[14] Note that agricultural lands have lost on average 50% of their carbon due to intensive cultivation and other damage of human origin.[7]

Fresh charcoal must first be "charged" before it can function as a biotope.[33] Several experiments demonstrate that uncharged charcoal can bring a provisional depletion of available nutrients when first put into the soil - until its pores fill with nutrients. This is overcome by soaking the charcoal for two to four weeks in any liquid nutrient (urine, plant tea, etc.).

Biochar[edit]

Biochar is high temperature charcoal produced from a biomass of wood and leafy plant materials in an environment with very low or no oxygen at all. Amending soil with biochar has been observed to increase the activity of arbuscular mycorrhizal fungi. Tests of high porosity materials such as zeolite, activated carbon, and charcoal show that microbial growth substantially improves with charcoal. It may be that small pieces of charcoal migrate within the soil, providing a habitat for bacteria that decompose the biomass in the surface ground cover.[34] This process may have an essential role in terra preta's self-propagation; a virtuous cycle develops as the fungus spreads from the charcoal, fixing additional carbon, stabilizing the soil with glomalin, and increasing nutrient availability for nearby plants.[35][36] Many other agents contribute, from earthworms to humans as well as the charring process.

If biochar becomes widely used for soil improvement, it will involve globally significant amounts of carbon sequestration, helping remediate global warming. "Bio-char soil management systems can deliver tradable C emissions reduction, and C sequestered is easily accountable, and verifiable."[37]

What should be considered the most unique part of the terra preta soil when compared to modern approach to reconciling soil fertility. Biochar is shown to have increased soil cation exchange capacity leading to improved plant nutrient uptake. Along with this it was particularly useful in the acidic tropical soils as it is capable of raising pH due to its slightly alkaline nature. Biochar also shows that, in relation to a soil, productivity of oxidised residue is particularly stable, abundant and entirely capable of increasing soil fertility levels.[38]

Biochar stability as a form of charcoal is due to its formation. The process of pyrolysis, the burning of organic material at high temperatures, and very low oxygen levels results in a porous char rich and ash poor product.[39] This through application to soil has potential to be a nutrient dense long term addition to soil fertility.

Organic matter and nutrients[edit]

Charcoal's porosity brings better retention of organic matter, of water and of dissolved nutrients,[29] as well as of pollutants such as pesticides and aromatic poly-cyclic hydrocarbons.[40]

Organic matter[edit]

Charcoal's high absorption potential of organic molecules (and of water) is due to its porous structure.[4] Terra preta's great quantity of charcoal supports a high concentration of organic matter (on average three times more than in the surrounding poor soils[4][25][30][41]), up to 150 g/kg.[14] Organic matter can be found at 1 to 2 metres (3 ft 3 in to 6 ft 7 in) deep.[18]

Gerhard Bechtold proposes to use terra preta for soils that show, at 50 centimeters (20 in) depth, a minimum proportion of organic matter over 2.0-2.5%. The accumulation of organic matter in moist tropical soils is a paradox, because of optimum conditions for degradation.[25] It is remarkable that anthrosols regenerate in spite of these tropical conditions' prevalence and their fast mineralisation rates.[14] The stability of organic matter is mainly due to the biomass being only partially consumed.[25]

Nutrients[edit]

Terra preta soils also show higher quantities of nutrients, and a better retention of these nutrients, than the surrounding infertile soils.[25] The proportion of P reaches 200–400 mg/kg.[42] The quantity of N is also higher in anthrosol, but that nutrient is immobilized because of the high proportion of C over N in the soil.[14]

The anthrosol's availability of P, Ca, Mn, and Zn is clearly higher than the neighbouring Ferrasol. The absorption of P, K, Ca, Zn, and Cu by the plants increases when the quantity of available charcoal increases. The production of biomass for two crops (rice and Vigna unguiculata (L.) Walp.) increased by 38–45% without fertilization (P < 0.05), compared to crops on fertilized Ferrasol.[14]

Amending with pieces of charcoal approximately 20 millimeters (0.79 in) in diameter, instead of ground charcoal, did not change the results except for manganese (Mn), for which absorption considerably increased.[14]

Nutrient drainage is minimal in this anthrosol, despite their abundant availability, resulting in high fertility. When inorganic nutrients are applied to the soil, however, the nutrients' drainage in anthrosol exceeds that in fertilized Ferralsol.[14]

As potential sources of nutrients, only C (via photosynthesis) and N (from biological fixation) can be produced in situ. All the other elements (P, K, Ca, Mg, etc.) must be present in the soil. In Amazonia the approvisionning in nutrients from composting in situ is excluded for natural soils heavily washed-out (ferralsols, acrisols, lixisols, arenosols, uxisols, etc.) that do not contain these elements in high concentration. In the case of terra preta, the only possible nutrient sources are primary and secondary. The following components have been found:[25]

  1. Human and animal excrements (rich in P and N);
  2. Kitchen refuse, such as animal bones and tortoise shells (rich in P and Ca);
  3. Ash residue from incomplete combustion (rich in Ca, Mg, K, P and charcoal);
  4. Biomass of terrestrial plants (e.g. compost); and
  5. Biomass of aquatic plants (e.g. algae).

Saturation in pH and in base is more important than in the surrounding soils.[42][43]

Microorganisms and animals[edit]

Bacteria and fungi (myco-organisms) live and die within the porous media, thus increasing its carbon content.

A significant biological production of black carbon has recently been identified, especially under moist tropical conditions. It is possible that the fungus Aspergillus niger is mainly responsible.[34]

The peregrine earthworm Pontoscolex corethrurus (Oligochaeta: Glossoscolecidae) ingests pieces of charcoal and mixes them in a finely ground form with the mineral soil. P. corethrurus is widespread in all Amazonia and notably in clearings after burning processes thanks to its tolerance of a low content of organic matter in the soil.[44] This as an essential element in the generation of terra preta, associated with agronomic knowledge involving layering the charcoal in thin regular layers favourable to its burying by P. corethrurus.

Some ants are repelled from fresh terra preta, their density of appearance is found to be low after about 10 days as compared to control soils.[45]

Modern research on creating terra preta[edit]

Perhaps the most important aspect of terra preta is not simply its historical interpretation and nostalgia but its modern application. This therefore is an area which is gaining more acknowledgment and research to discovering the secret behind recreating Amazonian black or dark earth.[46]

The rich earth consists of high levels of soil carbon the essential medium of fertile soils. A newly coined term attracting further research is ‘synthetic terra preta’.[47] A fertiliser consisting of materials thought to replicate the original materials, including; crushed clay, blood and bone meal, manure and biochar[47] The resultant mixture is of particulate nature meaning it is capable of moving down the soil profile and improving soil fertility and carbon amongst the current soil peds and aggregates over a viable time frame.[48] This mixture provides multiple aspects in at least reaching terra mulata a less fertile subset of terra preta. Due to it addressing many problems tropical and both world wide soil quality. Blood and bone meal and chicken manure are both useful for addition of short term organic manure addition.[49] But perhaps the most important and unique part of the improvement of the soil fertility was ‘While Carbonized biomass (pyrogenic carbon) is a principal constituent of terra preta that was, to our best knowledge, gradually incorporated into these soils, 4 to 10 thousand years ago.[50]

Perhaps the key is to generate this process in an economically viable manner that could be included in modern agriculture practices. Therefore the biochar is capable of decreasing acidity on soil and if soaked in nutrient rich liquid can slowly release nutrients, and provide habitat for microbes in soil due to high porosity surface area.[51] The future of terra preta is perhaps an important avenue of future carbon sequestration while reversing the current worldwide decline in soil fertility and associated desertification. However whether this is possible on a larger scale and the feasibility is yet to be concluded.

Average poor tropic soils are easily enrichable to terra preta nova by the addition of crumbled charcoal and condensed smoke.[52] Efforts to recreate these soils are being undertaken by private companies. Embrapa and other organizations in Brazil are working with terra preta.[53][54] Academic research efforts continue.[55]

See also[edit]

Notes[edit]

  1. ^ Kleiner, Kurt (2013). "The bright prospect of biochar : article : Nature Reports Climate Change". nature.com. Retrieved February 2, 2013. 
  2. ^ a b c "Discovery and awareness of anthropogenic amazonian dark earths (terra preta)", by William M. Denevan, University of Wisconsin–Madison, and William I. Woods, University of Kansas.
  3. ^ a b c Glaser, Bruno. "Terra Preta Web Site". 
  4. ^ a b c d e f g Glaser, Bruno (27 February 2007). "Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century". Philosophical Transactions of the Royal Society B 362 (1478): 187–196. doi:10.1098/rstb.2006.1978. PMC 2311424. PMID 17255028. Retrieved 4 May 2008. 
  5. ^ E.G. Neves, R.N. Bartone, J.B. Petersen & M.J. Heckenberger (2001). The timing of Terra Preta formation in the central Amazon: new data from three sites in the central Amazon. p. 10. 
  6. ^ a b "Historical Ecology and Future Explorations" in "Amazonian Dark Earths: origin, properties, and management" by J. Lehmann, N. Kaampf, W.I. Woods, W. Sombroek, D.C. Kern, T.J.F. Cunha et al., Chapter 23, 2003. (Clark Erickson), p. 484
  7. ^ a b c d e Day, Danny (2004). "Carbon negative energy to reverse global warming". Eprida. 
  8. ^ "Unnatural Histories - Amazon". BBC Four. 
  9. ^ Simon Romero (14 January 2012). "Once Hidden by Forest, Carvings in Land Attest to Amazon’s Lost World". The New York Times. 
  10. ^ Mann, C. C., ed. (2005). 1491: New Revelations of the Americas Before Columbus. University of Texas. p. 296. ISBN 1-4000-3205-9. 
  11. ^ a b Mann, C, C., ed. (2005). 1491: New Revelations of the Americas Before Columbus. University of Texas. ISBN 1-4000-3205-9. 
  12. ^ "Classification of Amazonian Dark Earths and other Ancient Anthropic Soils" in "Amazonian Dark Earths: origin, properties, and management" [1] by J. Lehmann, N. Kaempf, W.I. Woods, W. Sombroek, D.C. Kern, T.J.F. Cunha et al., Chapter 5, 2003. (eds J. Lehmann, D. Kern, B. Glaser & W.I. Woods); cited in Lehmann et al., 2003, pp. 77–102.
  13. ^ William I. Woods (soil biologist/archaeologist at the University of Kansas) estimates that around 10% of the original terra comum appears to have been converted to terra preta. Cited by Charles C. Mann in "1491", citation extract quoted here.
  14. ^ a b c d e f g h "Nutrient availability and leaching in an archaeological Anthrosol and a Ferralsol of the Central Amazon basin: fertilizer, manure and charcoal amendments", by J. Lehmann, J. Pereira da Silva Jr., C. Steiner, T. Nehls, W. Zech & Bruno Glaser. Plant and Soil 249: 343–357, 2003.
  15. ^ "TP Sites Known in Literature and by Surveys", by G. Bechtold
  16. ^ William Balée (anthropologist at Tulane University in New Orleans) " Earthmovers of the Amazon" by Charles C. Mann. Article in the series "News Focus" in SCIENCE, 4 February 2000, vol. 287: 786–789. This article presents archeological research in the Beni area, directly linked with the recent renewal of interest on terra preta, as well as photographs of experimental reconstructions of that mode of agriculture.
  17. ^ Mandin, Marie-Laure. "Vivre en Guyane" - compte rendu succint de découverte de sites de Terra preta en Guyane.". Retrieved 2 February 2013. 
  18. ^ a b [2] Terra Preta - Homepage about Anthrohumox in Brazilian Lowland - Research by Gerhard Bechtold.
  19. ^ "Smouldered-earth policy – Created by ancient Amazonian natives, dark soils retain abundant carbon." Article by B. Harder in [www.sciencenews.org Science News], 4 March 2006, vol. 169, p. 133.
  20. ^ a b "The molecularly uncharacterized component of nonliving organic matter in natural environments." by J.I. Hedges et al., 2000 Org. Geochem. 31, 945–958. (doi:10.1016/S0146-6380(00)00096-6). Cited by B. Glaser in "Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century".
  21. ^ "The identification of black carbon particles with the analytical scanning electron microscope: methods and initial results." P. Stoffyn-Egli, T.M. Potter, J.D. Leonard & R. Pocklington. 1997. Sci. Total Environ. 198, 211–223. (doi:10.1016/S0048-9697(97)05464-8). Cited by B. Glaser in "Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century".
  22. ^ "Hydrogen-deficient molecules in natural riverine water samples—evidence for the existence of black carbon in DOM." by S. Kim, L.A. Kaplan, R. Benner & P.G. Hatcher. 2004. Mar. Chem. 92, 225–234. (doi:10.1016/j.marchem.2004.06.042). Cited by B. Glaser in "Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century".
  23. ^ a b "Black carbon in soils: the use of benzenecarboxylic acids as specific markers", by B. Glaser, L. Haumaier, G. Guggenberger & W. Zech. 1998. Org. Geochem. 29, 811–819. (doi:10.1016/S0146-6380(98)00194-6). Cited by B. Glaser in "Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century"
  24. ^ W.I. Woods & J.M. McCann in Yearbook Conf. Latin Am. Geogr. Vol. 25 (ed. Caviedes, C.) 7–14. (Univ. Texas, Austin, 1999). Cited in "Putting the carbon back: Black is the new green" [3], article in Nature 442, 624-626, 10 August 2006. Link to article in the Biopact site: "Terra Preta: how fuels can become carbon-negative and save the planet".
  25. ^ a b c d e f g "The ‘Terra Preta’ phenomenon: a model for sustainable agriculture in the humid tropics." by B. Glaser, L. Haumaier, G. Guggenberger and W. Zech, 2001. Naturwissenschaften 88, 37–41 (doi:10.1007/s001140000193). Cited in "Weed composition and cover after three years of soil fertility management in the central Brazilian Amazon: Compost, fertilizer, manure and charcoal applications", by J. Major et al.
  26. ^ Christoph Steiner, EACU 2004
  27. ^ "Organic chemistry studies on Amazonian Dark Earths", by G. Guggenberger and W. Zech. Chapter 12 of "Amazonian Dark Earths: origin, properties, and management" by J. Lehmann, B. Glaser, N. Kaampf, W.I. Woods, W. Sombroek, D.C. Kern, T.J.F. Cunha et al. (eds J. Lehmann, D. Kern, B. Glaser & W. Woods 2003), pp. 227–241. Dordrecht, The Netherlands: Kluwer.
  28. ^ "Black carbon assessment using benzenepolycarboxylic acids: revised method", by S. Brodowski, A. Rodiodec, L. Haumaier, B. Glaser & W. Amelung. 2005. Org. Geochem. 36, 1299–1310. (doi:10.1016/j.orggeochem.2005.03.011).
  29. ^ a b c "Stability of soil organic matter in Terra Preta soils" by Bruno Glaser, Ludwig Haumaier,Georg Guggenberger and Wolfgang Zech, Institut de Sciences des Sols, University of Bayreuth, D-95440 Bayreuth, Germany.
  30. ^ a b "Ecological aspects of soil organic matter in tropical land use. In Humic substances in soil and crop sciences. Selected readings", by W. Zech, L. Haumaier et R. Hempfling. 1990 (eds P. McCarthy, C. E. Clapp, R. L. Malcolm & P. R. Bloom), pp. 187–202. Madison, WI: American Society of Agronomy and Soil Science Society of America. Cited by B. Glaser in "Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century".
  31. ^ "Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy for mapping nano-scale distribution of organic carbon forms in soil: Application to black carbon particles", by Johannes Lehmann, Biqing Liang, Dawit Solomon, Mirna Lerotic, Flavio Luizao, James Kinyangi, Thorsten Schafer, Sue Wirick, and Chris Jacobsen. Global Biogeochemical Cycles, vol. 19, GB1013, doi:10.1029/2004GB002435, published 16 February 2005.
  32. ^ "Slash-and-char: a feasible alternative for soil fertility management in the Central Amazon?", by Johannes Lehmann, Jose Pereir Da Silva Jr., Marco Rondon, Cravo Manoel Da Silva, Jacqueline Greenwood, Thomas Nehls, Christoph Steiner and Bruno Glaser. Symposium no. 13, Paper no. 449. 17e WCSS, 14–21 August 2002, Thailand.
  33. ^ "Everyone’s carbon sequestration: decrease atmospheric carbon dioxide, earn money and improve the soil." By Folke Günther, Holon Ecosystem Consultants, Lund, Sweden. Presented at the International Institute for Industrial Environmental Economics – IIIEE), 26 March 2007.
  34. ^ a b B. Glaser & K.-H. Knorr, not yet published as to early 2007, cited in "Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century", by Bruno Glaser
  35. ^ Controls on production, incorporation and decomposition of glomalin -- a novel fungal soil protein important to soil carbon storage. By Sara Wright, Soil Microbial Systems Laboratory. In "Summaries of FY 2000 Activities, Energy Biosciences, September 2001.
  36. ^ Plant-fungal interactions via Glomalin: A fungal protein that affects soil ecosystem cycling of C, N, P & S. By Jude Maul and Laurie Drinkwater (Cornell University, Ithaca, NY). ESA Annual Meeting 2005, Palais des congrès de Montréal, Contributed Oral Session 89: Soil Ecology: Plant - Soil Relationships., 10 August 2005.
  37. ^ JOHANNES LEHMANN, JOHN GAUNT, and MARCO RONDON; BIO-CHAR SEQUESTRATION IN TERRESTRIAL ECOSYSTEMS – A REVIEW; Mitigation and Adaptation Strategies for Global Change (2006) 11: 403–427
  38. ^ [Mao,. J., Johnson, R, Lehmann, J., Olk, D., Neves, E., Thompson, M. and Schmidr-Rohr, K. 2012. Abundant and stable char residues in soils: Implications for soil fertility and carbon sequestration. Environmental science \& technology, 46 (17), pp. 9571—9576]
  39. ^ Adrados, A., Lopez-Urionabarrenechea, A., Solar, J., Requies, J., De Marco, I. and Cambra, J. 2013. Upgrading of pyrolysis vapours from biomass carbonization. Journal of Analytical and Applied Pyrolysis.
  40. ^ "Biodegradation of two commercial herbicides (Gramoxone and Matancha) by the bacteria Pseudomonas putida", par M. Kopytko, G. Chalela & F. Zauscher. 2002. Elec. J. Biotechnol. 5, 182–195. Cited by B. Glaser in "Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century".
  41. ^ "Amazon soils. A reconnaissance of the soils of the Brazilian Amazon region", by W. G. Sombroek, 1966. vol. 672, p. 283. Wageningen, The Netherlands: Verslagen van Landbouw-kundige Onderzoekingen. Cited by B. Glaser in "Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century".
  42. ^ a b "Site Terra Preta de Índio - Soil Biogeochemistry" by Johannes Lehmann, Cornell University.
  43. ^ Sombroek, 1966; Smith, 1980; Kern and Kämpf, 1989; Sombroek et al., 1993; Glaser et al., 2000; Lehmann et al., 2003; Liang et al., 2006)
  44. ^ Jean-François Ponge, Stéphanie Topoliantz, Sylvain Ballof, Jean-Pierre Rossi, Patrick Lavelle, Jean-Marie Betsch and Philippe Gaucher (2006). "Ingestion of charcoal by the Amazonian earthworm Pontoscolex corethrurus: a potential for tropical soil fertility" (PDF). Soil Biology and Biochemistry 38 (7): 2008–2009. doi:10.1016/j.soilbio.2005.12.024. 
  45. ^ Reddy, N. Sai Bhaskar. "Terra Preta Roof-Top Experiments". 
  46. ^ [4] Jauss, J. 2013. Terra Preta de Indio.
  47. ^ a b Chia, C., Munroe, P., Joseph, S. and Lin, Y. 2010. Microscopic characterisation of synthetic Terra Preta. Soil Research, 48 (7), pp. 593—605
  48. ^ Adams, M., 2013. Securing soil through carbon. Sydney, University of Sydney.
  49. ^ Rahman, M. 2013. Nutrient use and Carbon Sequestration Efficiencies in Soils from different Organic. Wastes in Rice and Tomato Cultivation. Communications in Soil Science and Plant Analysis.
  50. ^ Madari, B. E., Cunha, T. J. F. & Soares, R., 2011. Organic matter of the anthropogenic dark earths of Amazonia. Dynamic Soil, Dynamic Plant , 5(1), pp. 21-28.
  51. ^ Mao, J., Johnson, R., Lehmann, J., Olk, D., Neves, E., Thompson, M. and Schmidt-Rohr, K. 2012. Abundant and stable char residues in soils: Implications for soil fertility and carbon sequestration. Environmental science \& technology, 46 (17), pp. 9571—9576.
  52. ^ Mann, Charles C. (September 2013). "Our Good Earth - National Geographic Magazine". ngm.nationalgeographic.com. Retrieved February 2, 2013. 
  53. ^ Embrapa Amazônia Ocidental, Embrapa Solos
  54. ^ NPA
  55. ^ Cornell University, University of Georgia, Universität Bayreuth, University of Florida, Iowa State University, Geoecology Energy Organisation

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