Terra Preta Research Articles

Selective extraction of humic acids from an anthropogenic Amazonian dark earth and from a chemically oxidized charcoal

Spectroscopic techniques including X-ray photoelectron spectroscopy (XPS) can identify particular chemical groups of humic acids (HA) from “Terra Preta de Indios” (TPI) or Amazonian dark earth, the highly fertile anthropogenic soil found in the Amazonian region. The high fertility and resilience of these soils cannot be explained by their chemically inert pyrogenic C content alone, but the natural aging of this C generates reactive carboxyl functional groups attached directly to the recalcitrant polycondensed aromatic backbone. Through spectroscopic techniques used in this work, the HA fraction (the alkaline-soluble organic matter that precipitates at low pH) of the TPI soil was compared with humic and fulvic acids, obtained by oxidizing activated charcoal with sodium hypochlorite. The yields recovery of HA-like substances was 12 and 28 wt% by using 10 and 20 cmol L−1 of oxidizing agent, respectively. X-ray photoelectron spectroscopy, energy dispersive X-ray, and solid-state 13C nuclear magnetic resonance (13C NMR) spectroscopies were used to evaluate the elements and structures present in all samples. XPS C 1 s spectra of HA extracted from TPI soil and from prepared HA showed aromatic structures (C = C and π–π* shake-up satellite peak) bounded to carboxyl groups (COOH). The morphology and polycondensation level of aromatic C were evaluated by scanning electron microscopy (SEM). The similarities of the spectra indicated that the used method was efficient to obtain an organic amendment similar to TPI soil organic matter.

Amazonian Dark Earths in the context of pre-Columbian settlements

Important information about pre-Columbian Amazonian settlement and economy provide Amazonian Dark Earths (ADE), black or brown soils characterized by the presence of charcoal in high concentrations, with highly elevated nutrients and organic matter and higher pH level. Usually ADE are related to large concentrations of ceramics, stone artifacts and animal remains. The main factor for the initiation of ADE formation was the long-lasted, fully sedentary pre-Columbian settlement. Its size and a form can be correlated with traces of historical human habitation. Thus, these sites can reflect the social organization of a specific group. Therefore, ADE studies can bring much valuable information concerning pre-Columbian settlement in Amazonia. st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:Standardowy; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:Times New Roman; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

Capacity of Aromatic Compound Degradation by Bacteria from Amazon Dark Earth

Amazon dark earth (ADE) is known for its high organic matter content, biochar concentration and microbial diversity. The biochar amount suggests the existence of microorganisms capable of degrading aromatic hydrocarbons (AHs). In an effort to investigate the influence of bacteria on the resilience and fertility of these soils, we enriched five ADE soils with naphthalene and phenanthrene, and biodegradation assays with phenanthrene and diesel oil were carried out, as well. After DNA extraction, amplification and sequencing of the 16S rRNA bacterial gene, we identified 148 isolates as the Proteobacteria, Firmicutes and Actinobacteria phyla comprising genera closely related to AHs biodegradation. We obtained 128 isolates that degrade diesel oil and 115 isolates that degrade phenanthrene. Some isolates were successful in degrading both substrates within 2 h. In conclusion, the obtained isolates from ADE have degrading aromatic compound activity, and perhaps, the biochar content has a high influence on this.

Assessment of bacterial bph gene in Amazonian dark earth and their adjacent soils.

Amazonian Anthrosols are known to harbour distinct and highly diverse microbial communities. As most of the current assessments of these communities are based on taxonomic profiles, the functional gene structure of these communities, such as those responsible for key steps in the carbon cycle, mostly remain elusive. To gain insights into the diversity of catabolic genes involved in the degradation of hydrocarbons in anthropogenic horizons, we analysed the bacterial bph gene community structure, composition and abundance using T-RFLP, 454-pyrosequencing and quantitative PCR essays, respectively. Soil samples were collected in two Brazilian Amazon Dark Earth (ADE) sites and at their corresponding non-anthropogenic adjacent soils (ADJ), under two different land use systems, secondary forest (SF) and manioc cultivation (M). Redundancy analysis of T-RFLP data revealed differences in bph gene structure according to both soil type and land use. Chemical properties of ADE soils, such as high organic carbon and organic matter, as well as effective cation exchange capacity and pH, were significantly correlated with the structure of bph communities. Also, the taxonomic affiliation of bph gene sequences revealed the segregation of community composition according to the soil type. Sequences at ADE sites were mostly affiliated to aromatic hydrocarbon degraders belonging to the genera Streptomyces, Sphingomonas, Rhodococcus, Mycobacterium, Conexibacter and Burkholderia. In both land use sites, shannon's diversity indices based on the bph gene data were higher in ADE than ADJ soils. Collectively, our findings provide evidence that specific properties in ADE soils shape the structure and composition of bph communities. These results provide a basis for further investigations focusing on the bio-exploration of novel enzymes with potential use in the biotechnology/biodegradation industry.

Chemical analysis and molecular models for calcium-oxygen-carbon interactions in black carbon found in fertile Amazonian anthrosoils.

Carbon particles containing mineral matter promote soil fertility, helping it to overcome the rather unfavorable climate conditions of the humid tropics. Intriguing examples are the Amazonian Dark Earths, anthropogenic soils also known as "Terra Preta de Índio'' (TPI), in which chemical recalcitrance and stable carbon with millenary mean residence times have been observed. Recently, the presence of calcium and oxygen within TPI-carbon nanoparticles at the nano- and mesoscale ranges has been demonstrated. In this work, we combine density functional theory calculations, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transformed infrared spectroscopy, and high resolution X-ray photoelectron spectroscopy of TPI-carbons to elucidate the chemical arrangements of calcium-oxygen-carbon groups at the molecular level in TPI. The molecular models are based on graphene oxide nanostructures in which calcium cations are strongly adsorbed at the oxide sites. The application of material science techniques to the field of soil science facilitates a new level of understanding, providing insights into the structure and functionality of recalcitrant carbon in soil and its implications for food production and climate change.

Characterization of an enriched biochar

Carbonized materials are responsible for maintaining a high level of fertility and soil organic matter in soils such as the Amazonian Dark Earths, also known as Terra Preta. It is hypothesized that an enriched biochar, which will have long term stability similar to Terra Preta, can be synthesized by mixing biochars with manures, minerals and clays and heating the mixture at low temperatures. This treatment will promote bonding between the mineral and the organic phases, which may occur naturally after several years of aging in soil. This paper describes the characterization of an enriched biochar by a range of analytical methods. Examination of the enriched biochar showed that it has high concentrations of exchangeable cations, available phosphorus and high acid neutralizing capacity. Structural analysis of the enriched biochar reveals a microstructure that suggests that bonding has indeed occurred between the biochar and mineral phases. Using natural 13C abundance and a two-pool exponential model, the half-life of enriched biochar-C was estimated to be 104 years in a clayey soil.

Fields of dreams Four Fields Tim Dee Jonathan Cape, 2013. 288 pp.

Fields of dreams <b>Four Fields</b> <i>Tim Dee</i> Jonathan Cape, 2013. 288 pp.

History and Technology of Terra Preta Sanitation

In order to reach the Millennium Development Goals for significantly reducing the number of people without access to adequate sanitation, new holistic concepts are needed focusing on economically feasible closed-loop ecological sanitation systems rather than on expensive end-of-pipe technologies. An analysis of a former civilization in the Amazon (nowadays Brazil) highlights the possibility to close the loop with a more sustainable lifestyle integrating soil fertility, food security, waste management, water protection and sanitation, renewable energy. Terra Preta do Indio is the anthropogenic black soil produced by ancient cultures through the conversion of bio-waste, fecal matter and charcoal into long-term fertile soils. These soils have maintained high amounts of organic carbon several thousand years after they were abandoned. Deriving from these concepts, Terra Preta Sanitation (TPS) has been re-developed and adopted. TPS includes urine diversion, addition of a charcoal mixture and is based on lactic-acid-fermentation with subsequent vermicomposting. Lacto-fermentation is a biological anaerobic process that generates a pre-stabilization of the mixture. The main advantage of lacto-fermentation is that no gas and no odor is produced. What makes it particularly interesting for in-house systems even in urban areas. Instead, vermicomposting is an aerobic decomposition process of the pre-digested materials by the combined action of earthworms and microorganisms. It transforms the carbon and nutrients into the deep black, fertile and stable soil that can be utilized in agriculture. No water, ventilation or external energy is required. Starting from ancient Amazonian civilizations traditional knowledge, the aim of this work is to present TPS systems adopted nowadays.

Amazonian Dark Earths in Western Amazonia?

Western Amazonia is a large region that includes a global biodiversity hotspot (the Yasuni National Park) and which still retains large tracts of intact native rainforest. Along the Napo River (Fig. 1), which originates in the Ecuadorian eastern lowlands and discharges into the Peruvian reaches of the Amazon River, current human settlement is uneven and highly dispersed. In Ecuador, towns are associated with the encroachment of oil extraction activities and the expansion of the agricultural frontier; small villages are found along an expanding road network and also dot the banks of the main rivers; and small groups of nomadic peoples, some in voluntary isolation from our industrialised society, inhabit the rugged interfluvial terrain beyond the main rivers. In Peru, small villages dot the middle reaches of the Napo River and its main tributaries, and there are also reports of indigenous groups in voluntary isolation. Larger settlements become more prevalent in the lower Napo, closer to the Amazon River and within reach of the road network leading to the Peruvian city of Iquitos.

Amazonian Dark Earths in the context of pre-Columbian settlements

Amazonian Dark Earths in the context of pre-Columbian settlements

Opportunities and constraints for biochar technology in Australian agriculture: looking beyond carbon sequestration

The application of biochar technology for soil amendment is largely based on evidence about soil fertility and crop productivity gains made in the Amazonian Black Earth (terra preta). However, the uncertainty of production gains at realistic application rates of biochars and lack of knowledge about other benefits and other concerns may have resulted in poor uptake of biochar technology in Australia so far. In this review, we identify important opportunities as well as challenges in the adoption of biochar technology for broadacre farming and other sectors in Australia. The paper highlights that for biochar technology to be cost-effective and successful, we need to look beyond carbon sequestration and explore other opportunities to value-add to biochar. Therefore, some emerging and novel applications of biochar are identified. We also suggest some priority research areas that need immediate attention in order to realise the full potential of biochar technology in agriculture and other sectors in Australia.

Estimating Amazonian Indian Numbers in 1492

Desde 1965 he hecho varios intentos para estimar la población nativa de la Amazonía en 1492. Mi método original fue determinar las densidades de cada hábitat, que se proyectan a los totales para la Gran Amazonia de 5.1 a 6. 8 millones. Ahora he rechazado este método, dado que las poblaciones más densas se agruparon sobre todo en vez de uniformemente dispersado. Sin embargo, sigo creyendo que un total de, al menos, cinco y seis millones es razonable, y hasta diez millones cuando se consideran densas poblaciones mantenidas por la terra preta .

Using proximal soil sensors and fuzzy classification for mapping Amazonian Dark Earths

We tested if hand-carried field proximal soil sensing (PSS) can be used to map the distribution of anthropogenic Amazonian Dark Earths (ADE). ADE soils are rich in archaeological artefacts, nutrients, organic matter and carbon in the very stable form of pyrogenic carbon, also referred to as black carbon or biochar. To test the capacity of PSS to detect signature ADE properties we measured electrical conductivity (ECa), magnetic susceptibility (MSa) and gamma ray data by transect sampling and compared these readings, using fuzzy classification, with datasets on chemical soil properties from a 28 ha large study area located on the Belterra Plateau of the Lower Amazon in northern Brazil. Results indicate that ECa and MSa measurements were good indicators of ADE signatures, but that the gamma radiation sensor was less useful in the deeply weathered soils. PSS and fuzzy classification can be used for rapid field mapping of ADE for both agricultural and archaeological purposes.

Moving forward from “biochar revolution” to “biochar evolution”: Shaping a promising mitigation tool demands future research efforts

In February 2013, the 2nd Nordic Biochar Seminar was successfully held in Helsinki, Finland. The fruitful meeting, well organized by Priit Tammeorg, offered a broad kaleidoscope of new insights into the novel interdisciplinary research topic of biochar. The papers in this issue clearly show that biochar use in agriculture can deliver benefits such as reductions in N2O emissions or N leaching (Kettunen and Saarnio), in addition to soil C storage without negative effects (Karer et al. , Anders et al. ). However, they also demonstrate that just one biochar addition does not turn each temperate fertile soil into a fertility miracle. In Terra preta sites, the pyrogenic carbon was likely an important ingredient, but it was combined with organic waste inputs and not used pure. Thus, yield-increasing pure-biochar effects in temperate soils are likely not a low-hanging fruit to be harvested without further ado. Rather, problematic soils should be the primary target; combined biochar-organics usage also deserves further research. However, considering the lack of political efforts to restore our planet's radiative balance, or tackle the challenges associated with soil degradation and resource consumption, no emerging chances should be missed. "Biochar" is such a chance – not more, but also not less. Shaping "biochar use in agriculture" into a safe, sustainable and economically feasible tool will only come at the cost of good hard research efforts; but it offers the unique chance to turn agricultural practices from being part of the problem into being part of the solution.

Mini-Review on Influence of Biochar for Sustainable Agriculture

Soil quality degradation is one of the most widespread phenomena for declining agricultural productivity throughout the world. It has been estimated that more than 40% of agricultural lands have been already become marginal due to mismanagement of soil. Biochar is a carbon rich product of a thermochemical conversion of biomass to be recognized as a beneficial soil amendment. It is not a novel soil amendment and history goes back to Mayan civilization called “Terra preta” soil. Due to the high fertility of these Amazon basin soils, many researchers in the world were interested in properties and application of biochar. This review gives an overview of agricultural benefits of biochar as a soil amendment. However, still there are many pros and cons of the application of biochar and this article will highlight the importance of further researches on the application of biochar as a soil amendment.

Dark earths and the human built landscape in Amazonia: a widespread pattern of anthrosol formation

Ancient anthrosols known as Amazonian dark earths or terra preta are part of the human built landscape and often represent valuable landscape capital for modern Amazonian populations in the form of fertile agricultural soils. The fertility, resilience, and large stocks of carbon in terra preta have inspired research on their possible role in soil fertility management and also serve as an example for a growing biochar industry it is claimed will sequester carbon for climate change mitigation. Although there is considerable scientific and public interest in terra preta, there is still much debate and little concrete knowledge of the specific processes and contexts of its formation. Research indicates that the formation of terra preta occurred mainly in midden deposits, themselves patterned around habitation areas, public areas, and routes of movement. Data from topographic mapping, soil analyses, and excavations in three regions of Amazonia demonstrate a widespread pattern of anthrosol formation in ring-shaped mounds surrounding flat terraces that extend across large areas of prehistoric settlements. It is hypothesized that there is a widespread type or types of occupation where the terraces were domestic areas (houses or yards) surrounded by refuse disposal areas in middens which built up into mounds over time, forming large deposits of terra preta and creating what could be called a ‘middenscape’. Initial results support the hypotheses, showing the interrelationship of residential and public areas, anthrosols, routes of movement, and natural resources. The patterning of anthrosols in ancient settlements indicates the use of space and can therefore serve as a basis for comparison of community spatial organization between sites and regions.

Properties of anthropogenic soils in ancient run-off capturing agricultural terraces in the Central Negev desert (Israel) and related effects of biochar and ash on crop growth

In the Central Negev hills (Israel) many ancient terraced wadis exist, which captured run-off and caused gradual soil aggradation, which enabled agricultural practices. In these terraces, dark colored soil horizons were observed, containing charcoal, as can be found in Terra Preta soils, suggesting higher fertility compared to natural soils. The aim of our investigation was to investigate these anthropogenic soils and to study the effects of charcoal and ash addition on soil properties and crop growth. We investigated 12 soil profiles, focusing on possible differences between light and dark colored soil horizons. We also investigated the effects of amendment of charcoal and ash on the growth of wheat (Triticum Aestivum L.) in a 40-day pot experiment involving two water regimes. Results show that charcoal content in light and dark horizons were both low (<0.2 %), but significantly lower bulk densities were found in dark colored horizons. In the crop experiment, charcoal addition resulted in decreased crop growth, while, in the water deficit regime, ash addition resulted in increased crop growth. Considering the observed charcoal and the results from the crop experiment, we hypothesize that, in ancient run-off capturing agricultural systems, ash was purposefully added as fertilizer.

The promise [and uncertainties] of Biochar

The promise [and uncertainties] of Biochar

Natural and Pyrogenic Humic Acids at Goethite and Natural Oxide Surfaces Interacting with Phosphate

Fulvic and humic acids have a large variability in binding to metal (hydr) oxide surfaces and interact differently with oxyanions, as examined here experimentally. Pyrogenic humic acid has been included in our study since it will be released to the environment in the case of large-scale application of biochar, potentially creating Darks Earths or Terra Preta soils. A surface complexation approach has been developed that aims to describe the competitive behavior of natural organic matter (NOM) in soil as well as model systems. Modeling points unexpectedly to a strong change of the molecular conformation of humic acid (HA) with a predominant adsorption in the Stern layer domain at low NOM loading. In soil, mineral oxide surfaces remain efficiently loaded by mineral-protected organic carbon (OC), equivalent with a layer thickness of ≥ ~0.5 nm that represents at least 0.1-1.0% OC, while surface-associated OC may be even three times higher. In natural systems, surface complexation modeling should account for this pervasive NOM coverage. With our charge distribution model for NOM (NOM-CD), the pH-dependent oxyanion competition of the organo-mineral oxide fraction can be described. For pyrogenic HA, a more than 10-fold increase in dissolved phosphate is predicted at long-term applications of biochar or black carbon.

The production, allocation and cycling of carbon in a forest on fertile terra preta soil in eastern Amazonia compared with a forest on adjacent infertile soil

Background: Terra preta do indio or ‘dark earth’ soils formed as a result of a long-term addition of organic matter by indigenous peoples in Amazonia. Aims: Here we report on the first study of productivity, allocation and carbon cycling from a terra preta plot in eastern Amazonia (Caxiuanã, Pará, Brazil), and contrast its dynamics with a nearby plot on infertile soil (ferralsols). Methods: We determined total net primary production (NPP) for fine roots, wood, and canopy and total autotrophic respiration (rhizosphere, wood, and canopy respiration) from two 1-ha plots on contrasting soils. Results: Both gross primary productivity (GPP) (35.68 ± 3.65 vs. 32.08 ± 3.46 Mg C ha−1 year−1) and carbon use efficiency (CUE) (0.44 ± 0.06 vs. 0.42 ± 0.05) were slightly higher at the terra preta plot. Total NPP (15.77 ± 1.13 Mg C ha−1 year−1 vs. 13.57 ± 0.60 Mg C ha−1 year−1) and rates of fine root production (6.41 ± 1.08 vs. 3.68 ± 0.52 Mg C ha−1 year−1) were also greater at the terra preta plot vs. the tower plot. Conclusions: Forests on terra preta soil fix slightly more carbon and allocate slightly more of that carbon towards growth than forests on the infertile plot, which leads to greater total NPP, which was disproportionately allocated to fine roots. However, since increased fine root NPP was partially offset by increased heterotrophic soil respiration, the increased root growth was unlikely to greatly enhance soil carbon stocks in terra preta soils.