Terra preta

Terra preta

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Terra preta is a type of very dark, fertile anthropogenic soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 found in the Amazon Basin
Amazon Basin
The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...

. Terra preta owes its name to its very high charcoal
Charcoal
Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...

 content, and was indeed made by adding a mixture of charcoal, bone, and manure to the otherwise relatively infertile Amazonian soil, and stays there for thousands of years. 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”. Terra mulata is lighter or brownish in color.

Terra preta is characterized by the presence of low-temperature charcoal in high concentrations; of high quantities of pottery sherd
Sherd
In archaeology, a sherd is commonly a historic or prehistoric fragment of pottery, although the term is occasionally used to refer to fragments of stone and glass vessels as well....

s; of organic matter such as plant residues, animal feces
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...

, fish and animal bones and other material; and of nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

s such as nitrogen (N)
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

, phosphorus (P)
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

, calcium (Ca)
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

, zinc (Zn)
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

, manganese (Mn)
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...

. It also shows high levels of microorganic
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

 activities and other specific characteristics within its particular ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

. It is less prone to nutrient leaching, which is a major problem in most rain forests. Terra preta zones are generally surrounded by terra comum, or "common soil"; these are infertile soils, mainly acrisol
Acrisol
An acrisol is a type of soil as classified by the Food and Agriculture Organization. It is clay-rich, and is associated with humid, tropical climates, such as those found in Brazil, and often supports forested areas. It is one of the 30 major soil groups of the World Reference Base for Soil Resources...

s, but also ferralsols and arenosols.

Terra preta soils are of pre-Columbian
Pre-Columbian era
The pre-Columbian era incorporates all period subdivisions in the history and prehistory of the Americas before the appearance of significant European influences on the American continents, spanning the time of the original settlement in the Upper Paleolithic period to European colonization during...

 nature and were created by humans between 450 BC and AD 950. The soil's depth can reach 2 metres (6.6 ft). Thousands of years after its creation it has been reported to regenerate itself at the rate of 1 centimetre (0.393700787401575 in) per year by the local farmers and caboclo
Caboclo
A caboclo or caboco is a person of a mixed Brazilian Indian and European ancestry. In Brazil, a caboclo is a specific type of mestiço as is the mulato, a person of a mixed Afro-Brazilian and European ancestry....

s in Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

's Amazonian basin, who seek it for use and for sale as valuable compost.

Early theories


The origins of the Amazonian dark earths were not immediately clear. One idea was that they resulted from ashfall from volcanoes in the Andes
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...

, since they occur more frequently on the brows of higher terraces. Another theory considered its formation as a result of sedimentation
Sedimentation
Sedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained, and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity, centrifugal acceleration...

 in tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...

 lakes or in recent ponds.

Anthropogenic roots


Because of their elevated charcoal content and the common presence of pottery remains, it is now widely accepted that these soils accreted near living quarters as residues from food preparation, cooking fires, animal and fish bones, broken pottery, etc., accumulated. The intentionality of the formation of terra preta has not been demonstrated, rather it formed under kitchen middens
Midden
A midden, is an old dump for domestic waste which may consist of animal bone, human excrement, botanical material, vermin, shells, sherds, lithics , and other artifacts and ecofacts associated with past human occupation...

. Areas used for growing crops 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 BC and AD 950 at sites throughout the Amazon Basin.

Pre-Columbian Amazonia


The Spanish
Spanish people
The Spanish are citizens of the Kingdom of Spain. Within Spain, there are also a number of vigorous nationalisms and regionalisms, reflecting the country's complex history....

 explorer Francisco de Orellana
Francisco de Orellana
Francisco de Orellana was a Spanish explorer and conquistador. He completed the first known navigation of the length of the Amazon River, which was originally named for him...

, the 16th century explorer who was the first European to traverse the Amazon River
Amazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...

, reported densely populated regions running hundreds of kilometers along the river, suggesting population levels exceeding even those of today. These populations left no lasting monuments, possibly because they used local wood as their construction material, which would have rotted in the humid climate (stone was unavailable). While it is possible Orellana may have exaggerated the level of development among the Amazonians, their semi-nomadic descendants have the odd distinction among tribal indigenous societies of a hereditary, yet landless, aristocracy
Aristocracy
Aristocracy , is a form of government in which a few elite citizens rule. The term derives from the Greek aristokratia, meaning "rule of the best". In origin in Ancient Greece, it was conceived of as rule by the best qualified citizens, and contrasted with monarchy...

, a historical anomaly for a society without a sedentary, agrarian culture. This suggests they once were more settled and agrarian but became nomadic after the demographic collapse
Population history of American indigenous peoples
The population figures for Indigenous peoples in the Americas before the 1492 voyage of Christopher Columbus have proven difficult to establish and rely on archaeological data and written records from European settlers...

 of the 16th and 17th century, due to European-introduced diseases, while still maintaining certain traditions. Moreover, many indigenous people adapted to a more mobile lifestyle in order to escape colonialism
Colonialism
Colonialism is the establishment, maintenance, acquisition and expansion of colonies in one territory by people from another territory. It is a process whereby the metropole claims sovereignty over the colony and the social structure, government, and economics of the colony are changed by...

. This might have made the benefits of terra preta, such as its self-renewing capacity, less attractive—farmers would not have been able to employ the renewed soil as they migrated for safety. Slash-and-char
Slash-and-char
Slash-and-char is an alternative to slash-and-burn that has a lesser effect on the environment. It is the practice of charring the biomass resulting from the slashing, instead of burning it as in the slash-and-burn practice....

 might have been an adaptation to these conditions.

For 350 years after the European arrival by Vicente Yáñez Pinzón
Vicente Yáñez Pinzón
Vicente Yáñez Pinzón was a Spanish navigator, explorer, and conquistador, the youngest of the Pinzón brothers...

, the Portuguese portion of the basin remained an untended former food gathering and planned agricultural landscape occupied by those who survived the epidemics. There is ample evidence for complex large-scale, pre-Columbian social formations, including chiefdoms, in many areas of Amazonia (particularly the inter-fluvial regions) and even large towns and cities. For instance the pre-Columbian culture on the island of Marajo
Marajó
Marajó is an island located at the mouth of the Amazon River in Brazil. It is part of the state of Pará.- Geography :With a land area of 40,100 km² , which compares to the size of Switzerland, it is the largest island to be completely surrounded by freshwater in the world...

 may have developed Social stratification
Social stratification
In sociology the social stratification is a concept of class, involving the "classification of persons into groups based on shared socio-economic conditions ... a relational set of inequalities with economic, social, political and ideological dimensions."...

 and supported a population of 100,000 people. Amazonians may have used terra preta to make the land suitable for the large scale agriculture needed to support large populations and complex social formations such as chiefdoms.

Location


Terra preta soils are found mainly in Brazilian Amazonia, where Sombroek et al. estimate that they cover at least 0.1 to 0.3%, or 6300 to 18900 km² (2,432.4 to 7,297.3 ) of low forested Amazonia); but others estimate this surface at 10.0% or more (twice the area of Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

).

Plots of terra preta exist in small plots averaging 20 hectares (49.4 acre), but areas of almost 900 acres (364.2 ha) 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 acre), see also 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
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

 and conservation.

Terra preta sites are also known in Ecuador
Ecuador
Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...

, Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

, French Guyana, in Benin
Benin
Benin , officially the Republic of Benin, is a country in West Africa. It borders Togo to the west, Nigeria to the east and Burkina Faso and Niger to the north. Its small southern coastline on the Bight of Benin is where a majority of the population is located...

, Liberia
Liberia
Liberia , officially the Republic of Liberia, is a country in West Africa. It is bordered by Sierra Leone on the west, Guinea on the north and Côte d'Ivoire on the east. Liberia's coastline is composed of mostly mangrove forests while the more sparsely populated inland consists of forests that open...

), and on the South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

n savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...

s. Similar dark earth
Dark earth
For the video game by the same name, see Dark Earth .Dark Earth in archaeology is an archaeological horizon often as much as 0.6m - 0.9m thick which covers Roman remains, notably in London and in Roman ruins in the rest of England, particularly urban ones...

 was found in late Roman Britain
Roman Britain
Roman Britain was the part of the island of Great Britain controlled by the Roman Empire from AD 43 until ca. AD 410.The Romans referred to the imperial province as Britannia, which eventually comprised all of the island of Great Britain south of the fluid frontier with Caledonia...

.

Pedology


Terra preta is defined as a type of latosol
Latosol
Latosol is a name given to soils found under tropical rainforests. They are red or yellowish-red in colour throughout and they do not have distinct horizons like a podsol. The red colour comes from the oxides of iron and aluminium which remain in the soil...

, having a carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 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. The varied features of the dark earths throughout the Amazon Basin suggest the existence of an extensive ancient native civilization dating back 500 to 2500 years.

Terra preta's capacity to increase its own volume—thus to sequester more carbon—was first documented by pedologist
Pedology (soil study)
Pedology is the study of soils in their natural environment. It is one of two main branches of soil science, the other being edaphology...

 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:
  1. Incorporation of wood charcoal
  2. Incorporation of organic matter and of nutrients
  3. Role of micro-organisms and animals in the soil

Wood charcoal


The transformation of biomass into charcoal produces a series of charcoal derivatives known as pyrogenic or black carbon
Black carbon
In Climatology, black carbon or BC is a climate forcing agent formed through the incomplete combustion of fossil fuels, biofuel, and biomass, and is emitted in both anthropogenic and naturally occurring soot. It consists of pure carbon in several linked forms...

, the composition of which varies from lightly charred organic matter, to soot
Soot
Soot is a general term that refers to impure carbon particles resulting from the incomplete combustion of a hydrocarbon. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolyzed fuel particles such as cenospheres,...

 particles rich in graphite
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...

 formed by recomposition of free radicals. Here, all types of charbonated materials are called charcoal. By convention, charcoal is considered to be any natural organic matter thermically transformed with an Oxygen/Carbon (O/C) percentage 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 with any certainty by determining only the proportion of O/C. The Hydrogen/Carbon percentage or molecular markers such as benzenepolycarboxylic acid, are therefore used as a second level of identification.

Early farmers added charcoal to poor soils, in the form of wood charcoal processed at low temperature and with a limited supply of oxygen (i.e., with smothered fires). 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 approximative average values of 50 mg/ha/m.

The chemical structure of charcoal in terra preta soils is characterized with poly-condensed aromatic groups, providing prolonged biological and chemical stability that sustains the fight against microbial degradation; it also provides, after partial oxidation, the highest nutrient retention. Wood charcoal (but not that from grasses or high cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 materials made at low temperature), thus has an internal layer of biological petroleum
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

 condensates that the bacteria consume, and that is similar to cellulose in its effects on microbial growth. Charring at high temperature loses that layer and brings little increase in soil fertility. The formation of condensed aromatic structures depends on the manufacture of charcoal. The slow oxidation of charcoal creates carboxylic group
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...

s; these increase the cations' exchange capacity
Cation exchange capacity
In soil science, cation-exchange capacity is the maximum quantity of total cations, of any class, that a soil is capable of holding, at a given pH value, for exchanging with the soil solution. CEC is used as a measure of fertility, nutrient retention capacity, and the capacity to protect...

 in the soil. The nucleus of black carbon particles produced by the biomass highly remains aromatic even after thousands of years in the soil and presents the spectral characteristics of fresh charcoal. Around that nucleus and on the surface of the black carbon particles, there were higher proportions of forms of carboxylic and phenol
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...

ic C
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

s 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
Sustainability
Sustainability is the capacity to endure. For humans, sustainability is the long-term maintenance of well being, which has environmental, economic, and social dimensions, and encompasses the concept of union, an interdependent relationship and mutual responsible position with all living and non...

 of terra preta. Soil amendments of Ferrasol with wood charcoal greatly increases productivity. Note that agricultural lands have lost in average 50% of their carbon due to intensive cultivation and other damage of human origin.

Fresh charcoal must first be “charged” before it can function as a biotope
Biotope
Biotope is an area of uniform environmental conditions providing a living place for a specific assemblage of plants and animals. Biotope is almost synonymous with the term habitat, but while the subject of a habitat is a species or a population, the subject of a biotope is a biological community.It...

. Several experiments demonstrate that uncharged charcoal can bring a provisional depletion of available nutrients when first put into the soil - until its pores fill with nutrients. This is overcome by soaking the charcoal for 2 to 4 weeks in any liquid nutrient (urine, plant tea, ...).

Biochar


Biochar
Biochar
Biochar or terra preta is charcoal created by pyrolysis of biomass. Biochar is under investigation as an approach to carbon sequestration via bio-energy with carbon capture and storage. Biochar thus has the potential to help mitigate climate change, via carbon sequestration...

 is low temperature charcoal produced from a biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

 of wood and leafy plant materials. Amending soil with biochar has been observed to increase the activity of arbuscular
Arbuscular mycorrhiza
An arbuscular mycorrhiza is a type of mycorrhiza in which the fungus penetrates the cortical cells of the roots of a vascular plant....

 mycorrhizal fungi. Tests of high porosity materials such as zeolite
Zeolite
Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents. The term zeolite was originally coined in 1756 by Swedish mineralogist Axel Fredrik Cronstedt, who observed that upon rapidly heating the material stilbite, it produced large amounts of steam from water that...

, activated carbon
Activated carbon
Activated carbon, also called activated charcoal, activated coal or carbo activatus, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions.The word activated in the name is sometimes replaced...

 and charcoal show that microbial growth substantially improves with charcoal. It may be that small pieces of charcoal migrate within the soil, providing a habitat for bacteria that decompose the biomass in the surface ground cover. This process may have an essential role in terra preta's self-propagation; a virtuous cycle develops as the fungus spreads from the charcoal, fixing additional carbon, stabilizing the soil with glomalin
Glomalin
Glomalin is a glycoprotein produced abundantly on hyphae and spores of arbuscular mycorrhizal fungi in soil and in roots.As a glycoprotein, glomalin stores carbon in both its protein and its carbohydrate subunits. It permeates organic matter, binding it to silt, sand, and clay particles...

, and increasing nutrient availability for nearby plants. Many other agents contribute, from earthworms to humans as well as the charring process.

If biochar becomes widely used for soil improvement, it will involve globally significant amounts of carbon sequestration, helping remediate global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...

. "Bio-char soil management systems can deliver tradable C emissions reduction, and C sequestered is easily accountable, and verifiable."

Organic matter and nutrients


Charcoal's porosity brings better retention of organic matter, of water and of dissolved organic nutrients, as well as of pollutants such as pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

s and aromatic poly-cyclic hydrocarbons.

Organic matter


Charcoal's high absorption potential of organic molecules (and of water) is due to its porous structure. Terra preta's great quantity 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 m (3.3 to 6.6 ) deep.

Gerhard Bechtold proposes to use terra preta for soils that show, at 50 centimetres (19.7 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 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 due to the biomass being only partially consumed.

Nutrients


Terra preta soils also show higher quantities of nutrients, and a better retention of these nutrients, than the surrounding infertile soils. The proportion of P
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

 reaches 200–400 mg/kg. The quantity of N
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 is also higher in anthrosol, but that nutrient is immobilized because of the high proportion of C
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 over N
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 in the soil.

The anthrosol's availability of P
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

, Ca
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

, Mn
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...

, and Zn
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

 is clearly higher than the neighbouring Ferrasol. The absorption of P
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

, K
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

, Ca
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

, Zn
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

, and Cu
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 by the plants increases when the quantity of available charcoal increases. The production of biomass for two crops (rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

 and Vigna unguiculata (L.) Walp.) increased by 38–45% without fertilization (P
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

 < 0.05), compared to crops on fertilized Ferrasol.

Amending with pieces of charcoal approximately 20 millimetre (0.78740157480315 in) in diameter, instead of ground charcoal, did not change the results except for manganese (Mn)
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...

, for which absorption considerably increased.

Nutrient drainage is minimal in this anthrosol, despite their abundant availability, 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
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 (via photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

) and N
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 (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 approvisionning in nutrients from composting in situ is excluded for natural soils heavily washed-out (Ferralsols, Acrisols, Lixisols, Arenosols, Uxisols, ...) that do not contain these elements in high concentration. In the case of terra preta, the only possible nutrient sources are primary and secondary. The following components have been found:
  1. Human and animal excrements (rich in P
    Phosphorus
    Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

     and N
    Nitrogen
    Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

    );
  2. Kitchen refuse, such as animal bones and tortoise
    Tortoise
    Tortoises are a family of land-dwelling reptiles of the order of turtles . Like their marine cousins, the sea turtles, tortoises are shielded from predators by a shell. The top part of the shell is the carapace, the underside is the plastron, and the two are connected by the bridge. The tortoise...

     shells (rich in P
    Phosphorus
    Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

     and Ca
    Calcium
    Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

    );
  3. Ash
    Ash (analytical chemistry)
    In analytical chemistry, ashing is the process of mineralization for preconcentration of trace substances prior to chemical analysis. Ash is the name given to all non-aqueous residue that remains after a sample is burned, and consist mostly of metal oxides....

    residue from incomplete combustion (rich in Ca
    Calcium
    Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

    , Mg
    Magnesium
    Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

    , K
    Potassium
    Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

    , P
    Phosphorus
    Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

     and charcoal);
  4. Biomass of terrestrial plants (e.g. compost
    Compost
    Compost is organic matter that has been decomposed and recycled as a fertilizer and soil amendment. Compost is a key ingredient in organic farming. At its most essential, the process of composting requires simply piling up waste outdoors and waiting for the materials to break down from anywhere...

    ); and
  5. Biomass of aquatic plant
    Aquatic plant
    Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or aquatic macrophytes. These plants require special adaptations for living submerged in water, or at the water's surface. Aquatic plants can only grow in water or in soil that is...

    s (e.g. algae
    Algae
    Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

    ).


Saturation in pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 and in base is more important than in the surrounding soils.

Microorganisms and animals


Bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 and fungi (myco-organisms) live and die within the porous media, thus increasing its carbon content.

A significant biological production of black carbon has recently been identified, especially under moist tropical conditions. It is possible that the fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

 Aspergillus niger
Aspergillus niger
Aspergillus niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food...

is mainly responsible.

The peregrine earthworm
Earthworm
Earthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female...

 Pontoscolex corethrurus (Oligochaeta
Oligochaeta
Oligochaeta is a subclass of animals in the biological phylum Annelida, which is made up of many types of aquatic and terrestrial worms, and this includes all of the various earthworms...

: Glossoscolecidae
Glossoscolecidae
Glossoscolecidae is a large family of earthworms which has native representatives in South and Central America. The species Pontoscolex corethrurus has a circumtropical distribution....

) ingests pieces of charcoal and mixes them in a finely ground form with the mineral soil. P. corethrurus is widespread in all 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 favourable to its burying by P. corethrurus.

Some ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...

s are repelled from fresh terra preta, their density of appearance is found to be low after about 10 days as compared to control soils.

Modern research on creating terra preta


Average poor tropic soils are easily enrichable to terra preta nova by the addition of crumbled charcoal and condensed smoke. Efforts to recreate these soils are being undertaken by multiple companies. Academic research efforts continue. Embrapa and other organizations in Brazil are working with terra preta.

See also

  • 1491: New Revelations of the Americas Before Columbus
    1491: New Revelations of the Americas Before Columbus
    1491: New Revelations of the Americas Before Columbus is a 2005 non-fiction book by American author and science writer Charles C. Mann about the pre-Columbian Americas...

  • Agroforestry
    Agroforestry
    Agroforestry is an integrated approach of using the interactive benefits from combining trees and shrubs with crops and/or livestock.It combines agricultural and forestry technologies to create more diverse, productive, profitable, healthy and sustainable land-use systems.-Definitions:According to...

  • Black Dirt Region
    Black Dirt Region
    The Black Dirt Region is located in southern Orange County, New York, USA and northern Sussex County, New Jersey. It is mostly located in the western section of the Town of Warwick, centered around the hamlet of Pine Island...

  • Ukrainian Chernozem
    Chernozem
    Chernozem , also known as "black land" or "black earth", is a black-coloured soil containing a high percentage of humus 7% to 15%, and high percentages of phosphoric acids, phosphorus and ammonia...

  • Lost City of Z
    Lost City of Z
    The Lost City of Z is the name given by Col. Percy Harrison Fawcett, a British surveyor, to a city that he thought existed in the jungle of the Mato Grosso region of Brazil...

  • Permaforestry
    Permaforestry
    Permaforestry is an approach to the wildcrafting and harvesting of the forest biomass that uses cultivation to improve the natural harmonious systems...

  • Terramare culture
    Terramare culture
    Terramare, Terramara or Terremare is a technology complex mainly of the central Po valley, in Emilia, northern Italy, dating to the Middle and Late Bronze Age ca. 1700-1150 BC. It takes its name from the "black earth" residue of settlement mounds. Terramare is from terra marna, "marl-earth", where...


External links