Terra preta (Portuguese pronunciation: [ˈtɛʁɐ ˈpɾetɐ], locally [ˈtɛha ˈpɾeta], literally "black soil" in Portuguese) is a type of very dark, fertile artificial (anthropogenic) soil found in the Amazon Basin. 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 soil of the Indian", "Indians' black earth"). Terra mulata ("mulatto earth") is lighter or brownish in color.
Terra preta owes its characteristic black color to its weathered charcoal content, and was made by adding a mixture of charcoal, bone, broken pottery, compost and manure to the low fertility Amazonian soil. A product of indigenous soil management and slash-and-char agriculture, the charcoal is stable and remains in the soil for thousands of years, binding and retaining minerals and nutrients.
Terra preta is characterized by the presence of low-temperature charcoal residues in high concentrations; of high quantities of tiny pottery shards; of organic matter such as plant residues, animal feces, fish and animal bones, and other material; and of nutrients such as nitrogen, phosphorus, calcium, zinc and manganese. Fertile soils such as terra preta show high levels of microorganic activities and other specific characteristics within particular ecosystems.
Terra preta zones are generally surrounded by terra comum ([ˈtɛhɐ koˈmũ] or [ˈtɛhɐ kuˈmũ]), or "common soil"; these are infertile soils, mainly acrisols, but also ferralsols and arenosols. Deforested arable soils in the Amazon are productive for a short period of time before their nutrients are consumed or leached away by rain or flooding. This forces farmers to migrate to an unburned area and clear it (by fire). Terra preta is less prone to nutrient leaching because of its high concentration of charcoal, microbial life and organic matter. The combination accumulates nutrients, minerals and microorganisms and withstands leaching.
Terra preta soils were created by farming communities between 450 BCE and 950 CE. Soil depths can reach 2 meters (6.6 ft). It is reported to regenerate itself at the rate of 1 centimeter (0.4 in) per year.
The origins of the Amazonian dark earths were not immediately clear to later settlers. 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.
Soils with elevated charcoal content and a common presence of pottery remains can accrete accidentally near living quarters as residues from food preparation, cooking fires, animal and fish bones, broken pottery, etc., accumulated. Many terra preta soil structures are now thought to have formed under kitchen middens, as well as being manufactured intentionally on larger scales. Farmed areas 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 BCE and 950 CE at sites throughout the Amazon Basin. More recent research found that terra preta may pre-date human habitation, suggesting that pre-Colombian people intentionally utilized these areas of high soil fertility.
Amazonians formed complex, large-scale social formations, including chiefdoms (particularly in the inter-fluvial regions) and even large towns and cities. For instance, the culture on the island of Marajó may have developed social stratification and supported a population of 100,000. Amazonians may have used terra preta to make the land suitable for large-scale agriculture.
Spanish explorer Francisco de Orellana was the first European to traverse the Amazon River in the 16th century. He reported densely populated regions extending hundreds of kilometres along the river, suggesting population levels exceeding even those of today. Orellana may have exaggerated the level of development, although that is disputed. The evidence to support his claim comes from the discovery of geoglyphs dating between 0–1250 CE and from terra preta. Beyond the geoglyphs, these populations left no lasting monuments, possibly because they built with wood, which would have rotted in the humid climate, as stone was unavailable.
Whatever its extent, this civilization vanished after the demographic collapse of the 16th and 17th century, due to European-introduced diseases such as smallpox. The settled agrarians again became nomads, while still maintaining specific traditions of their settled forbears. Their semi-nomadic descendants have the distinction among tribal indigenous societies of a hereditary, yet landless, aristocracy, a historical anomaly for a society without a sedentary, agrarian culture.
Moreover, many indigenous peoples adapted to a more mobile lifestyle 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 cultivate the renewed soil as they migrated. Slash-and-char agriculture may have been an adaptation to these conditions. For 350 years after the European arrival, the Portuguese portion of the basin remained untended.
Terra preta soils are found mainly in the Brazilian Amazon, where Sombroek et al. 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; but others estimate this surface at 10.0% or more (twice the area of Great Britain). Recent model-based predictions suggest that the extent of terra preta soils may be of 3.2% of the forest.
Terra preta exists in small plots averaging 20 hectares (49 acres), but areas of almost 360 hectares (890 acres) have also been reported. They are found among various climatic, geological, and topographical situations. Their distributions either follow main water courses, from East Amazonia to the central basin, 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 distribution map of terra preta sites in Amazon basin The spreads of tropical forest between the savannas could be mainly anthropogenic—a notion with dramatic implications worldwide for agriculture and conservation.
In the international soil classification system World Reference Base for Soil Resources (WRB) Terra preta is called Pretic Anthrosol. The most common original soil before transformed into a terra preta is the Ferralsol. Terra preta has a carbon content ranging from high to very high (more than 13–14% organic matter) in its A horizon, but without hydromorphic characteristics. Terra preta presents important variants. For instance, gardens close to dwellings received more nutrients than fields farther away. 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.
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. This remains the central mystery of terra preta.
The processes responsible for the formation of terra preta soils are:
- Incorporation of wood charcoal
- Incorporation of organic matter and of nutrients
- Growth of microorganisms and animals in the soil
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. All types of carbonized 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; smaller values have been suggested. Because of possible interactions with minerals and organic matter from the soil, it is almost impossible to identify charcoal by determining only the proportion of O/C. The hydrogen/carbon percentage or molecular markers such as benzenepolycarboxylic acid, are used as a second level of identification.
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). Other measurements found carbon levels 70 times greater than in surrounding ferralsols, with approximate average values of 50 Mg/ha/m.
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. 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. Charring at high temperature consumes that layer and brings little increase in soil fertility. The formation of condensed aromatic structures depends on the method of manufacture of charcoal. The slow oxidation of charcoal creates carboxylic groups; these increase the cations' exchange capacity of the soil. 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 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.
This charcoal is thus decisive for the sustainability of terra preta. Amending ferralsol with wood charcoal greatly increases productivity. Globally, agricultural lands have lost on average 50% of their carbon due to intensive cultivation and other damage of human origin.
Fresh charcoal must be "charged" before it can function as a biotope. Several experiments demonstrate that uncharged charcoal can bring a provisional depletion of available nutrients when first put into the soil, that is 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.).
Organic matter and nutrients
Charcoal's high absorption potential of organic molecules (and of water) is due to its porous structure. Terra preta's high concentration of charcoal supports a high concentration of organic matter (on average three times more than in the surrounding poor soils), up to 150 g/kg. Organic matter can be found at 1 to 2 metres (3 ft 3 in to 6 ft 7 in) deep.
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 organic matter degradation. It is remarkable that anthrosols regenerate in spite of these tropical conditions' prevalence and their fast mineralisation rates. The stability of organic matter is mainly because the biomass is only partially consumed.
Terra preta soils also show higher quantities of nutrients, and a better retention of these nutrients, than surrounding infertile soils. The proportion of P reaches 200–400 mg/kg. 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.
Anthrosol's availability of P, Ca, Mn and Zn is higher than 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) increased by 38–45% without fertilization (P < 0.05), compared to crops on fertilized ferralsol.
Amending with charcoal pieces 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.
Nutrient leaching is minimal in this anthrosol, despite their abundance, resulting in high fertility. When inorganic nutrients are applied to the soil, however, the nutrients' drainage in anthrosol exceeds that in fertilized ferralsol.
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 provisioning of nutrients from the decomposition of naturally available organic matter fails as the heavy rainfalls wash away the released nutrients and the natural soils (ferralsols, acrisols, lixisols, arenosols, uxisols, etc.) lack the mineral matter to provide those nutrients. The clay matter that exists in those soils is capable of holding only a small fraction of the nutrients made available from decomposition. In the case of terra preta, the only possible nutrient sources are primary and secondary. The following components have been found:
- Human and animal excrements (rich in P and N);
- Kitchen refuse, such as animal bones and tortoise shells (rich in P and Ca);
- Ash residue from incomplete combustion (rich in Ca, Mg, K, P and charcoal);
- Biomass of terrestrial plants (e.g. compost); and
- Biomass of aquatic plants (e.g. algae).
Microorganisms and animals
The peregrine earthworm Pontoscolex corethrurus (Oligochaeta: Glossoscolecidae) ingests charcoal and mixes it into a finely ground form with the mineral soil. P. corethrurus is widespread in Amazonia and notably in clearings after burning processes thanks to its tolerance of a low content of organic matter in the soil. This as an essential element in the generation of terra preta, associated with agronomic knowledge involving layering the charcoal in thin regular layers favorable to its burying by P. corethrurus.
Modern research on creating terra preta
Synthetic terra preta
A newly coined term is 'synthetic terra preta’. STP is a fertilizer consisting of materials thought to replicate the original materials, including crushed clay, blood and bone meal, manure and biochar is of particulate nature and capable of moving down the soil profile and improving soil fertility and carbon in the current soil peds and aggregates over a viable time frame. Such a mixture provides multiple soil improvements reaching at least the quality of terra mulata. Blood, bone meal and chicken manure are useful for short term organic manure addition. Perhaps the most important and unique part of the improvement of soil fertility is carbon, thought to have been gradually incorporated 4 to 10 thousand years ago. Biochar is capable of decreasing soil acidity and if soaked in nutrient rich liquid can slowly release nutrients and provide habitat for microbes in soil due to its high porosity surface area.
The goal is an economically viable process that could be included in modern agriculture. Average poor tropical soils are easily enrichable to terra preta nova by the addition of charcoal and condensed smoke. Terra preta may be an important avenue of future carbon sequestration while reversing the current worldwide decline in soil fertility and associated desertification. Whether this is possible on a larger scale has yet to be proven. Tree Lucerne (tagasaste or Cytisus proliferus) is one type of fertilizer tree used to make terra preta. Efforts to recreate these soils are underway by companies such as Embrapa and other organizations in Brazil.
Synthetic terra preta is produced at the Sachamama Center for Biocultural Regeneration in High Amazon, Peru. This area has many terra preta soil zones, demonstrating that this anthrosol was created not only in the Amazon basin, but also at higher elevations.
A synthetic terra preta process was developed by Alfons-Eduard Krieger to produce a high humus, nutrient-rich, water-adsorbing soil.
Terra preta sanitation
Terra preta sanitation (TPS) systems have been studied as an alternative sanitation option by using the effects of lactic-aid conditions in urine-diverting dry toilets and a subsequent treatment by vermicomposting.
- 1491: New Revelations of the Americas Before Columbus
- Archaeological horizon
- Belterra, Pará
- Black Dirt Region
- Ukrainian Chernozem
- Lost City of Z
- Terramare culture
- Denevan, William M.; Woods, William I. "Discovery and awareness of anthropogenic amazonian dark earths (terra preta)" (PDF). Archived from the original (PDF) on 24 September 2015.
- Mao, J.-D.; Johnson, R. L.; Lehmann, J.; Olk, J.; Neeves, E. G.; Thompson, M. L.; Schmidt-Rohr, K. (2012). "Abundant and stable char residues in soils: implications for soil fertility and carbon sequestration". Environmental Science and Technology. 46 (17): 9571–9576. Bibcode:2012EnST...46.9571M. CiteSeerX 10.1.1.698.270. doi:10.1021/es301107c. PMID 22834642.
Terra Preta soils consist predominantly of char residues composed of ~6 fused aromatic rings
- Dufour, Darna L. (October 1990). "Use of Tropical Rainforests by Native Amazonians". BioScience. 40 (9): 652–659. doi:10.2307/1311432. ISSN 0006-3568. JSTOR 1311432.
Much of what has been considered natural forest in Amazonia is probably the result of hundreds of years of human use and management.
Rival, Laura (1993). "The Growth of Family Trees: Understanding Huaorani Perceptions of the Forest". Man. 28 (4): 635–652. doi:10.2307/2803990. JSTOR 2803990.
- Kleiner, Kurt (2009). "The bright prospect of biochar : article : Nature Reports Climate Change". Nature.com. 1 (906): 72–74. doi:10.1038/climate.2009.48.
- Cornell University (1 March 2006). "Amazonian Terra Preta Can Transform Poor Soil into Fertile". Science Daily. Rockville, MD.
- Glaser, Bruno. "Terra Preta Web Site". Archived from the original on 25 October 2005.
- Glaser 2007.
- Watkins and Griffiths, J. (2000). Forest Destruction and Sustainable Agriculture in the Brazilian Amazon: a Literature Review (Doctoral dissertation, The University of Reading, 2000). Dissertation Abstracts International, 15–17
- Williams, M. (2006). Deforesting the Earth: From Prehistory to Global Crisis (Abridged ed.). Chicago, IL: The University of Chicago Press. ISBN 978-0-226-89947-3.
- Neves 2001, p. 10. sfn error: no target: CITEREFNeves2001 (help)
- Neves, E.G.; Bartone, R.N.; Petersen, J.B.; Heckenberger, M.J. (2001). The timing of Terra Preta formation in the central Amazon: new data from three sites in the central Amazon. p. 10.
- Lehmann, J.; Kaampf, N.; Woods, W.I.; Sombroek, W.; Kern, D.C.; Cunha, T.J.F. "Historical Ecology and Future Explorations". p. 484. in Lehmann et al. 2007
- Day, Danny (2004). "Carbon negative energy to reverse global warming". Eprida.
- Kawa, Nicholas C. (10 May 2016). Amazonia in the Anthropocene: People, Soils, Plants, Forests. University of Texas Press. ISBN 9781477308448.
- Silva, Lucas C. R.; Corrêa, Rodrigo Studart; Wright, Jamie L.; Bomfim, Barbara; Hendricks, Lauren; Gavin, Daniel G.; Muniz, Aleksander Westphal; Martins, Gilvan Coimbra; Motta, Antônio Carlos Vargas; Barbosa, Julierme Zimmer; Melo, Vander de Freitas (4 January 2021). "A new hypothesis for the origin of Amazonian Dark Earths". Nature Communications. 12 (1): 127. doi:10.1038/s41467-020-20184-2. ISSN 2041-1723.
- Mann 2005, p. 296.
- Mann 2005.
- Romero, Simon (14 January 2012). "Once Hidden by Forest, Carvings in Land Attest to Amazon's Lost World". The New York Times.
- "Unnatural Histories - Amazon". BBC Four.
- Lehmann, J.; Kaempf, N.; Woods, W.I.; Sombroek, W.; Kern, D.C.; Cunha, T.J.F. "Classification of Amazonian Dark Earths and other Ancient Anthropic Soils". pp. 77–102. in Lehmann et al. 2007
- Mann 2002 extract quoted here Archived 27 February 2008 at the Wayback Machine.
- McMichael, C. H.; Palace, M. W; Bush, M. B.; Braswell, B.; Hagen, S.; Neves, E.G.; Silman, M. R.; Tamanaha, E. K.; Czarnecki, C. (2014). "Predicting pre-Columbian anthropogenic soils in Amazonia". Proceedings of the Royal Society B: Biological Sciences. 281 (20132475): 1–9. doi:10.1098/rspb.2013.2475. PMC 3896013. PMID 24403329.
- Lehmann, J.; Pereira da Silva Jr., J.; Steiner, C.; Nehls, T.; Zech, W.; Glaser, Bruno (2003). "Nutrient availability and leaching in an archaeological Anthrosol and a Ferralsol of the Central Amazon basin: fertilizer, manure and charcoal amendments" (PDF). Plant and Soil. 249 (2): 343–357. doi:10.1023/A:1022833116184. S2CID 2420708.
- Bechtold, G. "Terra Preta Sites". www.gerhardbechtold.com. Retrieved 4 August 2018.
- Mann, Charles C. (4 February 2000). "Earthmovers of the Amazon". Science. 287 (5893): 1148–1152. doi:10.1126/science.321.5893.1148. PMID 18755950. S2CID 206581907. Archaeological 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.
- Mandin, Marie-Laure (January 2005). "Vivre en Guyane" - compte rendu succint de découverte de sites de Terra preta en Guyane" [Living in Guyana - summary report discovery of terra preta sites in Guyana] (PDF) (in French). Archived from the original (PDF) on 23 July 2013.
- Bechtold, Gerhard. "Gerhard Bechtold: Terra Preta". www.gerhardbechtold.com. Retrieved 5 August 2018.
- Harder, Ben (4 March 2006). "Smoldered-Earth Policy". Science News. 169 (9): 133. doi:10.2307/3982299. ISSN 0036-8423. JSTOR 3982299.
- Hedges, J.I; Eglinton, G; Hatcher, P.G; Kirchman, D.L; Arnosti, C; Derenne, S; Evershed, R.P; Kögel-Knabner, I; de Leeuw, J.W (October 2000). "The molecularly-uncharacterized component of nonliving organic matter in natural environments". Organic Geochemistry. 31 (10): 945–958. doi:10.1016/s0146-6380(00)00096-6. ISSN 0146-6380.
- Cited in Glaser 2007.
- Stoffyn-Egli, P.; Potter, T.M.; Leonard, J.D.; Pocklington, R. (May 1997). "The identification of black carbon particles with the analytical scanning electron microscope: methods and initial results". Science of the Total Environment. 198 (3): 211–223. Bibcode:1997ScTEn.198..211S. doi:10.1016/s0048-9697(97)05464-8. ISSN 0048-9697. Cited in Glaser 2007.
- Kim, Sunghwan; Kaplan, Louis A.; Benner, Ronald; Hatcher, Patrick G. (December 2004). "Hydrogen-deficient molecules in natural riverine water samples—evidence for the existence of black carbon in DOM". Marine Chemistry. 92 (1–4): 225–234. doi:10.1016/j.marchem.2004.06.042. ISSN 0304-4203. Cited in Glaser 2007.
- Glaser, B; Haumaier, L; Guggenberger, G; Zech, W (January 1998). "Black carbon in soils: the use of benzenecarboxylic acids as specific markers". Organic Geochemistry. 29 (4): 811–819. doi:10.1016/s0146-6380(98)00194-6. ISSN 0146-6380. Cited in Glaser 2007
- Woods, William I.; McCann, Joseph M. (1999). "The Anthropogenic Origin and Persistence of Amazonian Dark Earths". Yearbook. Conference of Latin Americanist Geographers. 25: 7–14. JSTOR 25765871. Cited in Marris 2006
- Glaser, Bruno; Haumaier, Ludwig; Guggenberger, Georg; Zech, Wolfgang (January 2001). "The 'Terra Preta' phenomenon: a model for sustainable agriculture in the humid tropics". Naturwissenschaften. 88 (1): 37–41. Bibcode:2001NW.....88...37G. doi:10.1007/s001140000193. ISSN 0028-1042. PMID 11302125. S2CID 26608101. Cited in MAJOR, JULIE; STEINER, CHRISTOPH; DITOMMASO, ANTONIO; FALCAO, NEWTON P.S.; LEHMANN, JOHANNES (June 2005). "Weed composition and cover after three years of soil fertility management in the central Brazilian Amazon: Compost, fertilizer, manure and charcoal applications". Weed Biology and Management. 5 (2): 69–76. doi:10.1111/j.1445-6664.2005.00159.x. ISSN 1444-6162.
- Steiner, Christoph. Plant nitrogen uptake doubled in charcoal amended soils. Energy with Agricultural Carbon Utilization Symposium, 2004.
- Guggenberger, G.; Zech, W. "Organic chemistry studies on Amazonian Dark Earths". in Lehmann et al. 2007
- Brodowski, S.; Rodionov, A.; Haumaier, L.; Glaser, B.; Amelung, W. (September 2005). "Revised black carbon assessment using benzene polycarboxylic acids". Organic Geochemistry. 36 (9): 1299–1310. doi:10.1016/j.orggeochem.2005.03.011. ISSN 0146-6380.
- Glaser, Bruno; Haumaier, Ludwig; Guggenberger, Georg; Zech, Wolfgang (4 August 2018). "Stability of soil organic matter in Terra Preta soils Stabilité de la matière organique dans les sols de Terra Preta". Institut de Sciences des Sols, University of Bayreuth. Cite journal requires
- Zech, W.; Haumaier, L.; Hempfling, R. (1990). "Ecological aspects of soil organic matter in tropical land use". In MacCarthy, Patrick (ed.). Humic substances in soil and crop sciences: selected readings : proceedings of a symposium cosponsored by the International Humic Substances Society ... Chicago, Illinois, 2 December 1985. American Society of Agronomy and Soil Science Society of America. pp. 187–202. ISBN 9780891181040. Cited in Glaser 2007.
- Lehmann, Johannes; Liang, Biqing; Solomon, Dawit; Lerotic, Mirna; Luizão, Flavio; Kinyangi, James; Schäfer, Thorsten; Wirick, Sue; Jacobsen, Chris (16 February 2005). "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". Global Biogeochemical Cycles. 19 (1): GB1013. Bibcode:2005GBioC..19.1013L. doi:10.1029/2004gb002435. ISSN 0886-6236.
- Lehmann, Johannes; Silva Junior, José; Rondon, Marco; Manoel Da Silva, Cravo; Greenwood, Jaqueline; Nehls, Thomas; Steiner, Christoph; Glaser, Bruno (1 January 2002). "Slash and Char: a feasible alternative for soil fertility management in the Central Amazon?". Cite journal requires
- Günther, Folke. "Folke Günther on ecological design,thermodynamics of living systems,ecological engineering, nutrient recycling and oil depletion". www.holon.se. Retrieved 5 August 2018.
- Pietikainen, Janna; Kiikkila, Oili; Fritze, Hannu (May 2000). "Charcoal as a habitat for microbes and its effect on the microbial community of the underlying humus". Oikos. 89 (2): 231–242. doi:10.1034/j.1600-0706.2000.890203.x. ISSN 0030-1299. Cited in Glaser 2007.
- Kopytko, M.; Chalela, G.; Zauscher, F. (2002). "Biodegradation of two commercial herbicides (Gramoxone and Matancha) by the bacteria Pseudomonas putida". Electronic Journal of Biotechnology. 5 (2): 182–195. doi:10.2225/vol5-issue2-fulltext-1. Cited in Glaser 2007.
- Sombroek 1966, p. 283 Cited in Glaser 2007.
- Lehmann, Johannes.som "Site Terra Preta de Índio - Soil Biogeochemistry", Cornell University.
- Sombroek 1966; Smith, 1980; Kern and Kämpf, 1989; Sombroek, Nachtergaele & Hebel 1993; Glaser et al. 2007; Lehmann et al. 2007; Liang et al. 2006
- Jean-François Ponge; Stéphanie Topoliantz; Sylvain Ballof; Jean-Pierre Rossi; Patrick Lavelle; Jean-Marie Betsch; 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.
- Reddy, N. Sai Bhaskar. "Terra Preta Roof-Top Experiments".
- Chia, C., Munroe, P., Joseph, S. and Lin, Y. 2010. Microscopic characterisation of synthetic Terra Preta. Soil Research, 48 (7), pp. 593—605
- Lehmann, Johannes. "Terra Preta de Indio". www.css.cornell.edu. Retrieved 7 August 2018.
- Adams, M. (2013), Securing soil through carbon., Sydney: University of Sydney
- Rahman, M. Mizanur (15 May 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. 44 (9): 1457–1471. doi:10.1080/00103624.2012.760575. ISSN 0010-3624. S2CID 96404482.
- Cunha, Tony Jarbas Ferreira; Madari, Beata Emoke; Canellas, Luciano Pasqualoto; Ribeiro, Lucedino Paixão; Benites, Vinicius de Melo; Santos, Gabriel de Araújo (February 2009). "Soil organic matter and fertility of anthropogenic dark earths (Terra Preta de Índio) in the Brazilian Amazon basin". Revista Brasileira de Ciência do Solo. 33 (1): 85–93. doi:10.1590/S0100-06832009000100009. ISSN 0100-0683.
- Mann, Charles C. (September 2013). "Our Good Earth - National Geographic Magazine". ngm.nationalgeographic.com.
- "Embrapa Amazônia Ocidental - Portal Embrapa". www.cpaa.embrapa.br. Retrieved 14 February 2018.
- "Sachamama". Archived from the original on 25 January 2016. Retrieved 20 January 2016.
- "Verfahren zur herstellung von humus- und nährstoffreichen sowie wasserspeichernden böden oder bodensubstraten für nachhaltige landnutzungs- und siedlungssysteme".
- Otterpohl, R.; Reckin, J.; Pieplow, H.; Buzie, C.; Bettendorf, T.; Factura, H. (2010). "Terra Preta sanitation: re-discovered from an ancient Amazonian civilisation – integrating sanitation, bio-waste management and agriculture". Water Science and Technology. 61 (10): 2673–2679. doi:10.2166/wst.2010.201. PMID 20453341.
- Lehmann, Johannes; Kern, Dirse C.; Glaser, Bruno; Woods, William I., eds. (8 May 2007). Amazonian Dark Earths: Origin Properties Management. Springer Science & Business Media. ISBN 9781402025976.
- Arroyo-Kalin, Manuel. "Geoarchaeological approaches to the study of Terras Pretas". Archived from the original on 30 October 2008. Retrieved 10 July 2008.
- Bechtold, G. "Research work, homepage and thesis about Terra Preta with maps of TP sites and TP field work in Belterra, Pará".
- Casselman, Anne (May 2007). "Special Report: Inspired by Ancient Amazonians, a Plan to Convert Trash into Environmental Treasure". Scientific American.
- Glaser, Bruno; Balashov, Eugene; Haumaier, Ludwig; Guggenberger, Georg; Zech, Wolfgang (July 2007). "Black carbon in density frations of anthropogenic soils of the Brazilian Amazon region". Organic Geochemistry. 31 (7–8): 669–678. doi:10.1016/s0146-6380(00)00044-9. ISSN 0146-6380.
- 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.
- Haywood, David (5 May 2007). "Could the Mysterious Agricultural Techniques of an Ancient Amazonian Civilization Make New Zealand Farming More Competitive?". Public Address Radio.
- Liang, Biqing; Lehmann, Johannes; Solomon, Dawit; Kinyangi, J; Grossman, Julie; B, O’Neill; JO, Skjemstad; Thies, Janice; FJ, Luizão (1 September 2006). "Black Carbon Increases Cation Exchange Capacity in Soils". Soil Science Society of America Journal. 70 (5): 1719–1730. Bibcode:2006SSASJ..70.1719L. doi:10.2136/sssaj2005.0383.
- Mann, C. C. (2005). 1491: New Revelations of the Americas Before Columbus. University of Texas. ISBN 978-1-4000-3205-1.
- Mann, Charles C. (1 March 2002). "1491". The Atlantic. Retrieved 5 August 2018.
- Marris, Emma (August 2006). "Black is the new green". Nature. 442 (7103): 624–626. Bibcode:2006Natur.442..624M. doi:10.1038/442624a. ISSN 0028-0836. PMID 16900176. S2CID 30544497.
|Wikimedia Commons has media related to Terra preta.|
- Sombroek, Wim G.; Nachtergaele, Freddy O.; Hebel, Axel (1993). "Amounts, Dynamics and Sequestering of Carbon in Tropical and Subtropical Soils". Ambio. 22 (7): 417–426. JSTOR 4314120.
- Tennesen, Michael (April 2007). "Black Gold of the Amazon". Discover Magazine. Vol. 28 no. 4.
- "Eprida: Sustainable Solutions for Global Concerns". www.eprida.com. Retrieved 5 August 2018.
- "The Secret of El Dorado". www.bbc.co.uk. BBC. Retrieved 5 August 2018.
- "Terra Preta". Hypography discussion forum. Archived from the original on 8 April 2008. Retrieved 8 May 2006.
- "Terra Preta Home Page". Retrieved 20 April 2007.
- "BioEnergy Lists: Biochar Mailing Lists | Sharing technical and event information about Biochar from the Biochar email lists". terrapreta.bioenergylists.org. Retrieved 5 August 2018.
- Sombroek, W.G. (1966). Amazon soils : a reconnaissance of the soils of the Brazilian Amazon region (phd). 672. Pudoc. p. 283.
- Schiermeier, Quirin (August 2006). "The hundred billion tonne challenge". Nature. 442 (7103): 620–623. doi:10.1038/442620a. ISSN 0028-0836. PMID 16900175. S2CID 26649615.
- Salleh, Anna (28 June 2007). "Charred farm waste could gobble up carbon". News in Science. Australian Broadcasting Corporation. ABC Science Online.
- Horstman, Mark (23 September 2007). "Agrichar – A solution to global warming?". ABC TV Science: Catalyst. Australian Broadcasting Corporation.
- Terra Preta Amazonian Earth Interview with Dr. Bruno Glaser in META magazine
- Terra Preta Program Website of Wageningen University