PRETIC - The new WRB diagnostic horizon for Amazonian Dark Earths

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WRB for anthropic topsoils in Amazonian Dark Earths

1 PRETIC - The new WRB diagnostic horizon for Amazonian Dark Earths A new diagnostic horizon in WRB for anthropic topsoils in Amazonian Dark Earths (South America) Anjos, Lúcia Helena C. dos, UFRRJ; Teixeira, Wenceslau.G., Embrapa Soils; Schad, Peter, Technische Universitaet Muenchen; Fontana, Ademir, Embrapa Soils

2 Why a new horizon for Amazonian Dark Earths? The Amazonian Dark Earths (ADE), also called Terra Preta de Índio, are classified according to WRB as Anthrosols (IUSS Working Group WRB, 2006) Different studies attribute to them the hortic, plaggic or terric horizon according to base saturation, extractable P content, amount of artefacts, animal activity, and other soil diagnostic criteria. However they do not fit the central concept of any of them: - deep cultivation, intensive fertilization and/or long-continued application of human and animal wastes and other organic residues (hortic horizon); - addition of sods (topsoil layers together with vegetation) and animal manure (plaggic horizon); - addition of earthy manures, compost, beach sands or mud (terric horizon).

Characteristics of the ADEs? The ADEs are associated to pre-columbian Amerindian settlements and have been reported mainly in the Amazon region.

and total phosphorus, calcium, magnesium, micronutrients (mainly zinc and manganese) and other metals as strontium and barium.

3 Characteristics of the ADEs? The ADEs are associated to pre-columbian Amerindian settlements and have been reported mainly in the Amazon region. They are variable in terms of depth of the diagnostic horizon, physical and chemical properties, but mostly have dark colors, high stocks of organic carbon, extractable and total phosphorus, calcium, magnesium, micronutrients (mainly zinc and manganese) and other metals as strontium and barium. TPI Rosa de Fogo Rio Preto da Eva - AM Contrasting with natural soils in the surrounding area, the surface horizons influenced by human activities have extraordinarily high CEC and nutrient availability. Artefacts TPI Rio Preto da Eva

(constructions, gardens), shell mounds ( sambaquis ),

4 Characteristics of the ADEs? Artefacts of ceramic, stones and bones and pieces of charcoal are frequently found mixed into the soil. Clear evidences of past human occupation in the landscape (constructions, gardens), shell mounds ( sambaquis ), earthworks (geoglyphs) are identifiable. Sambaqui Camacho 05_ Caldeirão, P Sambaqui fluvial Miracatu

5 Rationale for a new Horizon! Amazon Dark Earths Distribution (Teixeira, Wenceslau G.)

6 Rationale for a new Horizon! The ADEs may not show the evidences of animal activity required for the hortic horizons, and they were not influenced by manuring, as required for the hortic horizons, since this activity was not part of the pre-columbian Amerindian culture. Additionally, the surface anthropic horizons typical for the ADE show a high base saturation (BS); the base cations were added from bones (Ca), ashes, and many other organic materials (i.e. kitchen middens, palm leaves, human feces). Horizons, depth (cm) Color Corg g/kg Clay g/kg Base cations Ca+Mg cmol c /kg CEC A Y 2.5/ A Y 3/ AB Y 4/ B Y 7/ BS % P mg/kg Ferralsol, P18 (TB11-00), Humaita Apuí, Amazon; 7º 51 29,6 S and 61º 17 52,8 WGr (Cunha, 2005)

7 Pretic Horizon (2014, update 2015) Pretic (from Portuguese preto, black) General description A pretic is a mineral surface horizon that results from human activities including the addition of charcoal. It is characterized by its dark colour, the presence of artefacts (ceramic fragments, lithic instruments, bone or shell tools etc.) and high contents of organic carbon, phosphorus, calcium, magnesium and micronutrients (mainly zinc and manganese), usually contrasting with natural soils in the surrounding area. It typically contains visible remnants of charcoal. Pretic horizons are for example widespread in the Amazon Basin, where they are the result of pre- Columbian activities and have persisted over many centuries despite the prevailing humid tropical conditions and high organic matter mineralization rates.these soils with a pretic horizon are known as Terra Preta de Indio or Amazonian Dark Earths. They generally have high organic carbon stocks. Many of them are dominated by low-activity clays. Diagnostic criteria: A pretic horizon is a surface horizon consisting of mineral material and has: 1. a Munsell colour value of 4 and a chroma of 3, both moist; and 2. 1% organic carbon; and 3. a base saturation (by 1 M NH 4 OAc, ph 7) of 50%; and 4. exchangeable Ca plus Mg (by 1 M NH 4 OAc, ph 7) of 2 cmol c kg -1 fine earth; and mg kg -1 of extractable P (Mehlich-1); and

8 Pretic Horizon (2014, update 2015) Pretic (from Portuguese preto, black) 6. one or more of the following: a. 1% artefacts (by volume, by weighted average); or b. 1% charcoal (by volume, by weighted average); or c. evidences of past human occupation in the surrounding landscape, e.g. constructions, gardens, shell mounds ( sambaquis ), or earthworks (geoglyphs); and 7. < 25% (by volume) of animal pores, coprolites or other traces of soil animal activity; and 8. one or more layers with a combined thickness of 20 cm. Additional characteristics Charcoal is an artefact only if it is intentionally manufactured by humans. Relationships with some other diagnostics Pretic horizons do not show the animal activity required for hortic and irragric horizons. The diagnostic criteria for P concentrations in pretic and hortic horizons are based on different analytical methods with a lower requirement for the pretic horizon. The high base saturation sets the pretic horizon apart from plaggic horizons. It cannot be excluded that a pretic horizon fulfils also the criteria of the plaggic horizon. In this case, the soil scientist should use historical knowledge for making the final decision, whether the horizon is called plaggic or pretic. Some pretic horizons may qualify as mollic or umbric horizons.

9 Anthrosols Perfil Terra Preta Indio, Lago do Limão, Ago 2004

Argissolo Amarelo Distrófico A antrópico,

Ca 1 Mg 1 Zn 2 Mn 2 Au1 0-40 2.4 56 6.44 0.

11 Argissolo Amarelo Distrófico A antrópico, Caldeirão, Iranduba, AM Hor cm %C P mg kg -1 Ca 1 Mg 1 Zn 2 Mn 2 Au Au Au Bt cmol c kg -1, 2 mg kg -1

mg kg -1 Ca* Mg* Aup 0-14 1.07 47 3.8 0.6 Au1 14-41 0.79 36 3.6 0.

12 Other classes Lixic Pretic Xanthic Ferralsol (Hypereutric, Amphiloamic, Vetic) ARGISSOLO AMARELO Distrófico antrópico plintossólico Hor cm %C P mg kg -1 Ca* Mg* Aup Au Au *cmol c kg -1 Perfil XI RCC Roraima, Rorainópolis

Dark Earths (ADE), and their classification;

criteria (WRB, updated 2015); Studies on

are this soils limited to this area of Brazil?

13 What is the next step? Database of soils identified as Amazonian Dark Earths (ADE), and their classification; To test properties and limits of diagnostic criteria (WRB, updated 2015); Studies on different environments, beyond Amazon region; are this soils limited to this area of Brazil? How about other regions of the world? How widespread are the Dark Earths?

Acknowledgement Photos, courtesy from Wenceslau

br> and colleagues from different Institutions

Ácidos húmicos de solos escuros da Amazônia (TPI).

14 Acknowledgement Photos, courtesy from Wenceslau Geraldes Teixeira and colleagues from different Institutions Analytical data from: Cunha, T.J.F., Ácidos húmicos de solos escuros da Amazônia (TPI). Thesis UFRRJ CPGA-CS. 138p. Introduction Characteristics ADEs Rationale Pretic Horizon Anthrosols

Chernozems Kastanozems Phaeozems Peter Schad

Chernozems Kastanozems Phaeozems Peter Schad Soil Science Department of Ecology Technische Universität München Steppes dry, open grasslands in the mid-latitudes seasons: - humid spring and early summer