Germany

Terra Preta: Homepage about Anthrohumox in Brazilian Lowland
Gerhard Bechtold, University of Bayreuth/Munchen, Germany, November 2007
Consultant for National (Geo-)Information Systems and Database Setup, for Natural
Resources Assessments


GIS MAP of Terra Preta Sites in the Amazon
Summary of Thesis about Anthrohumox in Brazilian Lowland (2007)


In the Amazon lowland, Oxisol developed in scattered areas to ‘Indian Black Earth’ (Portuguese: ‘ Terra Preta’). High content of C (more than 9%) and ceramics are characteristics. Furthermore, they show weak acidity (but pH not over 6.5), low solum weight and high cation exchange capacity. The very most soil parameters are correlating with the percentage of C.


Terra Preta soil patterns can be found in the Amazon lowland ( map, based on literature research). Visited TP spots in Belterra (close to Santarem) show characteristics about their extension (seldom more than 2 acre), their depth (till about 50 cm with black color of value 3 or lower, in traces till 2-3 m depth) and their transition to the surrounding Oxisols (some few km). Size is correlating with intensity (low value – large areas) and frequency of ceramics in most cases. Due to oxic horizon in the lower Terra Preta, great group ‘Anthrohumox’ is proposed.


There are various theories about their origin. It is proved indeed, that Terra Preta is man made (high phosphate content, ceramics, situation on former village sites). About 1500-2800 years ago the Indios of the area had a strong influence on the Oxisols by their garbage, kitchen, compost and/or mulch ‘farming’ for a couple of hundreds years on their dwelling sites. C14 tests of the samples showed ages of 1780 (+ 270) and of 2260 (+ 280) years, thus dating back to between 800 BC and 500 AD.


Intensive activity of organisms and bioturbation cause a breaking up, a lowering of the solum weight, the loss of some hundred kg soil material per square m and of fine particles (‘only’ 65-80 % clay). High sand content indicates high C content (not in terms relative to other areas). All those characteristics decrease with increasing soil depth.


Strong impact of humic acids react a strong weathering of Si, Al and Fe. Different leaching ratios are discussed in the paper. They show a stronger weathering in the Terra Preta than in the Oxisol (lower Si, higher Al and Fe content). Al occurs mainly as 1:1 mineral (the main parent material), Fe as hematite or –favored by organic material – as goethite (over 70 % Fe d:Fe t).


Strong weathering (Aw climate) causes some characteristics at the depth functions of Si, Al, Fe, but leaching and cristallization is retarded by strong chelation (humic acids complex with metal ions). M o:M d relations quote always high (especially in Al and Mn, less in Fe). Very pronounced peaks of Al o (and of Fe o) are difficult to explain. Illuviation and podzolation seem to be very active. Different chelating groups (M(OH)++ or M(OH)2+) with different stabilities are more reasonable.
Very strong is the influence of the organic material on the content of Mn, Ca, Mg in the upper layers existing a manifold content, compared to the lower horizons, more than 10 times at Ca, due to the exchange sites of the organic substance (high solubility and erosion). At Mg existing fixation in anorganic compounds, e.g. Mg-Al-hydroxydes, at K in mineral interlayers are responsible for the lower percentages of the exchangeable to the total.


The vertical transition to the Oxisol depends on the element: Terra Preta and Oxisol have an almost identical C content at a depth of 1.50 – 2.00 m, an identical solum weight at 2.30 m depth, identical texture only at depths of more than 4 m, identical acidity and Si content at 2 m, Mn and K 40 – 50 cm, Ca and Mg at 1.50 m.


An exceptional profile with nodular laterite concretions (plinthic, plateau laterite) on a slope was analysed. It was found to have high C content and plenty of ceramics (therefore, Terra Preta), but in acidity and exchange capacity (content of K, Ca, Mg) it is more similar to Oxisols. In a different TP profile, burned charcoal induced high C contents and other characteristics of the upper horizons of Terra Preta.


At many elements it is possible to recognize, beside the organic influence, a ‘basic content’ (very low at nutrients) of Ca with 200 – 300 ppm, Mg with 180 – 190 ppm, K with 200 – 300 ppm, K with 50 ppm etc. A melioration by mobilization of these reserves is impossible.


Melioration is imaginable by pH raising (of soil and vegetation), addition of organic substances without fast mineralization and higher bioturbation.


Further research about Terra Preta, surrounding conditions of their development and analytics are described in the paper.

www.biochar.org - balance carbon and restore soil fertility
Christoph Steiner, Germany

Tracing black carbon in soil using SEM/EDX, biomarker analyses, and compound-specific radiocarbon analyses
S. Brodowski (1), P. M. Grootes (2), W. Zech (3), W. Amelung (1)

Mollisols are known to contain stable, black humus components which originate from
charred or coal-derived particles. As such black carbon (BC) significantly affects soil
fertility and interferes with models on soil organic matter dynamics, an accurate prediction of BC input into soils and an elucidation of the mechanisms of BC turnover
is essential. The main aims of this study were (i) to identify the sources of BC in the

Energy & Agricultural Carbon Utilization: Sustainable Alternatives to Sequestration
University of Georgia, Athens, Georgia, June 10-11, 2004

Oral Presentations

Discovery and Awareness of Anthropogenic Amazonian Dark Earths (Terra Preta)
Bill Denevan - Prof. Emeritus, University of Wisconsin at Madison, Madison, WI USA

Explorations of Pre-Columbian Agricultural Landscapes in the Amazon
Clark Erickson - Associate Professor of Anthropology, University of Pennsylvania, Philadelphia, PA USA

The Secrets of Making Terra Preta Soils

Terra Preta Homepage, Dark earths, Red Indian black earth
University of Bayreuth, Bayreuth, Germany 2002

Terra Preta (do indio) is a black earth-like anthropogenic soil with enhanced fertility due to high levels of soil organic matter (SOM) and nutrients such as nitrogen, phosphorus, potassium, and calcium embedded in a landscape of infertile soils (see soil profiles below). Terra Preta soils occur in small patches averaging 20 ha, but 350 ha sites have also been reported. These partly over 2000 years old man made soils occur in the Brazilian Amazon basin and other regions of South America such as Ecuador and Peru but also in Western Africa (Benin, Liberia) and in the savannas of South Africa. Terra Preta soils are very popularby the local farmers and are used especially to produce cash crops such as papaya and mango, which grow about three times as rapid as on surrounding infertile soils.