Terra preta

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Self-made terra preta : garden compost with soil and charcoal (see arrows)

Terra preta ( Portuguese for "black earth") or Terra preta de índio ("black Indian earth") is the name of a fertile anthropogenic soil found in the Amazon basin , more precisely a Pretic Anthrosol . The floor consists of a mixture of wood and vegetable coal , human feces, manure and compost , interspersed with fragments of pottery and occasionally bone and fish feathered .

Due to the color and the proportion of pyrogenic carbon , terra preta is also known as the Amazonian Indian black earth, but from a pedological point of view it is not black earth .

distribution

The main distribution areas of Terra preta concentrate on the areas of the shifting field economy with fire cultivation in the humid tropics. They are proven in South America (Brazil, Colombia, Ecuador, French Guiana) with a land area of ​​approx. 154 square kilometers. They are often found in former settlement areas in the immediate vicinity of the river.

Similar phenomena are also known in other parts of the world, for example in Africa (Ghana, Sierra Leone, Liberia, Guinea), Southeast Asia (Indonesia) and also in Europe (Germany and Sweden).

Terra preta floors were created in a centuries-long process and used intensively. In addition, their discovery is often cited as an example of the quantitative approach of the cultural landscape debate, which is intended to prove that even parts of so-called primeval forests have been anthropogenically changed.

According to an optimistic estimate by geographer William I. Woods , based on proven occurrences, up to ten percent of the surface of the Amazon basin could be covered by dark earth; Conservative estimates, on the other hand, only assume 0.1 to 0.3 percent. This suggests that the Amazon basin could once have housed five to ten million people. Most of the dark soils were created between 700 and 1000 AD, and some date well before the beginning of our era.

Emergence

In the humid tropics, weathering is very rapid due to the high temperatures . In addition, many floors are very old and therefore very badly weathered. Ferralsoles are formed , which are dominated by kaolinite as well as aluminum and iron oxides . Plant nutrients have been largely washed out , and nutrients introduced can hardly be stored. In addition, organic substances are quickly broken down and mineralized due to the high temperatures.

Terra preta is created by the long-term entry of ash, biomass, kitchen waste, charring residues, pyrogenic carbon, bones, dung and human feces. Organic matter is partially broken down, stabilized and shifted deeper ( bioturbation ) by microorganisms and soil animals . This creates horizons up to two meters thick .

An important component for the genesis of terra preta is biochar, which makes up around 20% of the carbon and contributes to stability through its slow degradation (approx. 2,000 years); however, nutrients and microorganisms are also required to develop and maintain them.

properties

Terra preta has two important properties with regard to soil fertility and its ability to store carbon: It is able to store high amounts of nutrients. For nitrogen this is 17 t / ha and for phosphorus 13 t / ha; this is twice as much nitrogen or four times as much phosphorus as in surrounding ferralsoles. In addition, it already contains an average of 250 t / ha of organic carbon and 50 t / ha of biochar, correspondingly three times more or seventy times more than surrounding ferralsole.

Potential for efficient use of resources

Newly created terra preta (Terra preta nova) could increase the yields of agriculturally unproductive soils. The biomass required to produce the biochar would have to be obtained from harvest residues or plantations, because the use of primary primeval forests does not make sense for ecological reasons. It is therefore proposed to generate further biochar via pyrolysis . However, this can produce toxic polycyclic aromatic hydrocarbons which, when the coal is introduced into the soil, can lead to a corresponding contamination of the soil; therefore the product should be checked. During pyrolysis, a liquid creosote is produced , which can also contain carcinogenic substances, and a pyrolysis gas, dominated by the flammable gases CO, H 2 and CH 4 .

In view of the scarcity of the biomass that can be sensibly used for charring, there is a risk that biochar will be used in the soil if it is widely used - and possibly promoted - that valuable wood stocks or even contaminated chargeable waste will be used for pyrolysis.

research

Terra Preta project on the sand in Tübingen

Since the first scientific description of terra preta by anthropologists and geographers (1871, 1903), soil scientists have turned to research into terra preta from the middle of the 20th century. For some years now, the scientific investigation of terra preta has been intensified, also in Europe.

In the archeology of the Amazon basin, the occurrence of terra preta is an important indicator of human settlement activity.

There are numerous projects around the world that deal with the properties of terra preta; these include Terra Preta Wageningen , ClimaCarbo , Terra BoGa and the Ithaka Institute.

See also

literature

  • Bruno Glaser , William I. Woods: Amazonian dark earths - explorations in space and time. Springer, Berlin 2004. ISBN 3-540-00754-7
  • Johannes Lehmann: Amazonian dark earths - origin, properties, management. Kluwer Academic, Dordrecht 2003. ISBN 1-4020-1839-8
  • Eije Erich Pabst: Terra preta. A contribution to the genesis discussion on the basis of field work among Tupi peoples of the Amazon. Dissertation, 184 pages, Kassel 1993.
  • Ute Scheub, Haiko Pieplow, Hans-Peter Schmidt: Terra Preta. The black revolution from the rainforest. Oekom, Munich 2013. ISBN 3-8658-1407-7

Web links

Commons : Terra preta  - collection of images, videos and audio files

Individual evidence

  1. ↑ Terra preta - wonder earth for the Wendland . Die Reportage, NDR, ARD, 2013. Retrieved on August 21, 2016.
  2. ↑ Odor in Commercial Scale Compost: Literature Review and Critical Analysis  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link / www.ecy.wa.gov  
  3. ↑ Christoph Steiner: Slash and Char as Alternative to Slash and Burn. Dissertation, Cuvillier Verlag, Göttingen 2007, ISBN 978-3-86727-444-9 . Pp. 13-17
  4. ^ Charles C. Mann : 1491: New Revelations of the Americas Before Columbus. 2nd Edition. Vintage Books, New York 2011, p. 355. Even if only 0.1 to 0.3 percent of the Amazon basin were covered with terra preta , this would correspond to several thousand to tens of thousands of square kilometers - a comparable area would be enough in the heartland of the Mesoamerican Maya culture to feed millions of people (ibid., p. 355).
  5. ↑ Kurt de Swaaf: Black Legacy - The dark earths of South America are slowly revealing their secrets , Neue Zürcher Zeitung, Research and Technology, February 18, 2015
  6. ↑ Glaser et al. (2003) Organic Chemistry Studies on Amazonian Dark Earths. In: Lehmann, J., Kern, D., Glaser, B., Woods, W. (Eds.): Amazonian Dark Earths: Origin, Properties, and Management. Dordrecht, The Netherlands: Kluwer, pp. 227-241 ISBN 978-1402018398
  7. ↑ Bruno Glaser , Ludwig Haumaier, Georg Guggenberger, Wolfgang Zech: The 'Terra Preta' phenomenon: a model for sustainable agriculture in the humid tropics . In: Natural Sciences . 88, No. 1, January 2001, pp. 37-41. ISSN 0028-1042 . doi : 10.1007 / s001140000193 .  
  8. ^ Bruno Glaser: Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century . In: Philosophical Transactions of the Royal Society B: Biological Sciences . 362, No. 1478, February 28, 2007, pp. 187-196. ISSN 0962-8436 . doi : 10.1098 / rstb.2006.1978 .  
  9. ↑ The European Biochar Certificate: The European biochar certificate. Retrieved February 19, 2020 .
  10. ↑ Constanze Werner et al .: Biogeochemical potential of biomass pyrolysis systems for limiting global warming to 1.5 ° C. 2018, Environmental Research Letters , 13 (4), 044036. doi: 10.1088 / 1748-9326 / aabb0e
  11. ^ Teichmann: Climate protection through biochar in German agriculture: potentials and costs. Retrieved February 19, 2020 .
  12. ↑ BUND: Terra Preta / Pyrolysekohle: BUND assessment of their environmental relevance. Retrieved February 19, 2020 .
  13. ↑ Eije Erich Pabst: Terra preta. A contribution to the genesis discussion on the basis of field work among Tupi peoples of the Amazon. Kassel 1993: p. 15.
  14. ↑ "Wonder Earth" in the test in Zeit-Online 49/2011
  15. ↑ Terra Preta Wageningen
  16. ↑ BMBF: ClimaCarbo. CO 2 -negative energy generation and closure of regional material cycles in the rural area of ​​Wendland. From March 2012 to December 2015. Accessed February 10, 2020.
  17. ↑ project Boga the Free University of Berlin
  18. ^ Ithaca Institute