Terra preta

Terra preta ( Portuguese for " black earth " ) or Terra preta do indio is a more appropriate to the Amazon basin, anthropogenic soil, more precisely called a Hortic anthrosol. The soil consists of a mixture of wood and coal plants, human feces, manure and compost interspersed with fragments of pottery and occasionally bones and fish bones.

Because of the color and the proportion of pyrogenic carbon Terra preta is also known as Indian Black Earth Amazonia, is from pedological point of view but no black earth.

Dissemination

The main distribution areas of terra preta focus on the humid tropics. Proved they are in South America ( Brazil, Colombia, Ecuador, French Guiana), with a land area of approximately 154 km ², which corresponds to a rate of 3.2 %. They often find themselves in former settlement areas in the immediate vicinity of rivers. Similar phenomena are also known in other continents, such as in Africa (Ghana, Sierra Leone, Liberia, Guinea ), South -East Asia (Indonesia) and Europe ( Germany, Sweden).

Formation

In the humid tropics soils of auswaschenden effect of precipitation are exposed and organic substances are degraded and mineralized rapidly due to the high temperatures. This results lateritic soils ( Ferralsols ) consisting mainly of aluminum and iron oxides. These soils contain almost no plant nutrients more and save introduced nutrients in a form only poorly available to plants.

Terra Preta is caused by long-standing record of ash, biomass, kitchen waste, Verkohlungsrückständen, fumed carbon, bone and human feces. By microorganisms and soil animals a part of the organic matter is decomposed (mineralization), stabilized and in the depth shifts ( bioturbation ). This results in up to 2 m thick horizons.

The most important part in the genesis of Terra preta is biochar, which contributes to Stabiliät by their slow degradation (about 2000 years); to the emergence and preservation but also nutrients and microorganisms are needed.

Properties

The Terra preta has two important properties in terms of soil fertility and its capacity to store carbon: So she's capable of storing large quantities of nutrients. For nitrogen this is 17t/ha and phosphorus 13t/ha; this is 2 times more nitrogen or 4 times more phosphorus than surrounding Ferralsols. It also contains an average 250t/ha organic carbon and 50t/ha biochar, corresponding to 3 times more, or 70 times more than surrounding Ferralsols.

These properties are excellent conditions for intensive and sustainable agriculture in the humid tropics.

Potential for efficient use of resources

New Terra preta created ( Terra preta nova ) could increase yields agriculturally unproductive soils. The need to produce biochar biomass would have to be obtained from crop residues or plantations, if only because the use of primary forests ( in addition to the devastating environmental impacts ) would be unproductive because of their low net growth. The problem is that the global area under cultivation is limited and probably already for other competing uses, such as the cultivation of biomass for energy purposes is not sufficient. An important additional benefit of biochar would contribute to the reduction of greenhouse gases ( methane, nitrous oxide, carbon dioxide). In addition to carbon dioxide, it would also be possible to reduce nitrogen oxide emissions, because less nitrogen fertilizer would be lost from the soil by leaching.

All components for the creation of Terra preta are known, but it is not yet possible, this soil on a large scale and in a short time " manufacture " because gigantic amounts of nutrients are needed for that. Instead, the Terra preta concept can be used to sustainably recycle natural resources ( particularly nutrient-rich wastes such as sewage sludge and organic waste ).

Research

Since the first scientific description of Terra preta by anthropologists and geographers (1871, 1903) soil scientists researching the Terra preta have turned from the mid-20th century. For several years, the scientific study of Terra preta has been intensified, even in Europe. Terra Preta is currently receiving media attention due to a possible contribution to the solution of global warming and food security.

Worldwide, there are numerous projects that deal with the Terra preta phenomenon; including, but not Terra Preta Wageningen, Climacarbo and Terra BoGa.