TERRA PRETA OR the use of Charcoal for the Sustained fertility of India’s soils

Bernard and Deepika

Aurobrindavan Auroville 605101 India

Background InformationONTERRA PRETA

Terra Preta is a dark coloured, very fertile and apparently self maintaining anthropogenic soil found in large tracts of the Amazon forest. So far conventional research has not yet been able to recreate Terra Preta or to find out how Terra Preta was made by the erstwhile inhabitants of the Amazon basin. (1)

Dark and fertile anthropogenic soils are encountered in many places around the world, for instance the well known “plaggen” soils in the Flanders and Holland. The most spectacular anthropogenic dark soil however is Terra Preta. This dark earth, created more then thousand years ago by the erstwhile Amer-Indians- una gente In Dios*- is characterized by an enduring and self regenerating fertility. It has evolved through human action,starting from one of the world’s poorest soils, most prone to degradation, into a living soil, unequalled anywhere else on the planet. What is so surprising about Terra Preta is that contrary to the plaggen soils, where sods were taken and brought from the heather, Terra Preta has evolved in situ without sod or soil amendment brought from “outside”.

These amazing soils keep on producing abundant and nearly perfect crops year after year without fertilization or plant protection worth a name. Another fact as spectacular as it is doubtful is that they seem to grow at an estimated 1% per year ! (2) On top of that they absorb carbon from the atmosphere and inhibit the release of methane, otherwise a normal feature of all soils, especially of chemically treated agri-soils.

In 1492Indiawas called Hindustan. The word Indian may have been derived from In Dios.

Although the secret of Terra Preta has not yet been fully unraveled, it is now certain that charcoal is the main agent that has brought about this astounding transformation. It is most likely, as research has recently indicated, that the “Gente In Dios” mixed charcoal with organic debris, excreta and kitchen wastes. Minerals derived from hand crushed rocks like feldspar and other rocks found on the banks of the Amazon rivers could equally have played an important role in the genesis of Terra Preta. It seems likely to us that a consorted action of physical, biological and energetic nature could lead to an equivalent of Terra Preta.

In other words, it is possible that the composition or arrangement of the physical components such as charcoal etc. has invited a dynamism that has brought about that very intense biological activity so characteristic of Terra Preta soils.

Equally also of special interest is to note that large parts of the AmazonForest are of anthropogenic origin.

The Problem of Soil Degeneration in the Tropics.

Soil degradation is one of the most serious problems of agricultural land use in the tropics. Most tropical soils are old and deeply weathered, having been cultivated for ages on end. In such soils, because of high temperatures and humidity, rapid mineralization of organic matter takes place. Heavy seasonal rainfall causes severe leaching of this mineralized organic matter and of primary soil minerals. The fact that photosynthesis is reduced in the monsoon season- the sky is overcast- aggravates this condition.

Under tropical conditions soil degeneration is accelerated by a factor of 100 in comparison to temperate zones. In organic farming, soil degradation may be somewhat less rapid because organic matter is held by the clay mineral complex. It demands nevertheless constant attention and substantial inputs of organic matter to keep up level performance.

Soil degeneration remains theunaddressed and unsolved problem in tropical soil fertility management up to this date.

CHARCOAL FOR REGENERATING TROPICAL SOILS

Biochar

Biochar is the charring of farm residues. As a soil amendment it has become the new fashion of our times and a good way to make money. While the benefits of applying charcoal to agricultural soils are real and beyond doubt, it is necessary to be aware of a few pitfalls covered over with this apparently good sounding word and intention. Two key issues need to be understood

These are the problems of first charring farm residues, known as biochar and second land grab for carbon sequestration. Charring farm residues instead of composting them would be detrimental to the fertility of India’s soils. Charcoal must be seen as an addition to composting not as a replacement.

Also under cover of mitigating a supposed global warming due to human interference, there exists in certain biochar circles an attempt to highjack “marginal soils” in tropical countries. This would as ever displace the local farmers, a socially unacceptable proposition. The motive for such a scandalous landgrab is establishing wood-monocultures, converting them into charcoal for sequestration. Obviously it is especially for grabbing the notorious carbon credits.

The ultimate way to extract carbon from the atmosphere, besides providing food security and food safety, is the full scale shifting to organic farming on a global scale, there is no other way.

Charcoal

Sources indicate that possibly 10% of the Terra Preta soils consist of charcoal.

Charcoal is a very porous material obtained by charring wood or other sources of biomass. One gram of charcoal can have an internal surface of up to 500 square meters depending on the base materials, the efficiency and type of the charring process. It is certain that the use of charcoal can substantially improve soil fertility.

Charcoal as a soil improver has traditionally been used in South-East Asia. The oldest description on charcoal use in agriculture is found in a text book, Nogyo Zensho (Encyclopedia of Agriculture) written by Yasusada Miyazaki of Japan in 1697. He remarks; “After roasting every wastes, the dense excretions (meaning human excreta) should be mixed with it and stocked for a while. This manure is efficient for the yields of any crops. It is called the ash manure”. Probably similar knowledge has been popular in China and Korea since ancient time. (3).

However here also ground facts have to be addressed. The danger of over exploiting the already scarce vegetative cover for the production of charcoal is very real and cannot be ignored. For this reason the promotion of charcoal as a soil conditioner must be preceded or at least go hand in hand not only with the creation of on farm woody biomass plantation e.g. bamboo but also and equally important with an awareness about environmental regeneration. It is in this context that the re-greening of village commons or the forestation of the 50 million Ha. of waste lands –rather wasted lands- becomes so crucial for the sustained fertility of India’s agricultural soils.

The effect of Charcoal on Tropical Soils

In the process of making charcoal, nutrients contained in the plant sap get fixed in the charcoal. Enzymes produced by bacteria that live in symbiosis with plant roots can mobilize these nutrients and make them available for plants. In return plants secrete nourishing substances for these bacteria.

Its big internal surface allows charcoal to store a huge quantity of ions and so prevent leaching of nutrients from soil organic matter and of primary soil minerals. This is especially of importance in soils with clays of low internal surface. Owing to its porous structure charcoal also holds water readily, making it important for soil moisture conservation. Charcoal provides thus an ideal niche for micro organisms like Arbuscular Mycorrhiza that produce glomalin and for all kinds of soil bacteria.

Further, charcoal, due to its high exchange capacity, can absorb and fix mineral ions coming withthe rain water. The soil bacteria associated with the root hairs can then again through their enzymic action release these nutrients. In this way, the trace minerals always present in rainwater become actually a fertilizing agent which provides for long lasting, i.e. sustainable soil fertility (4). It is interesting to note that charcoal remains stable in the soil for an estimated 5.000 to 50.000 years. It can be considered an almost permanent sink of carbon and is thus the ultimate in carbon sequestration (5).

The high monsoon rainfall and temperatures cause organic matter to mineralize very fast in tropical soils. At the same time the overcast sky cuts of sunlight and reduces the photo synthetic activity of plants. There occurs thus an excess of available nutrients which are consequently leached down.

Recent research has shown that addition of charcoal to very poor soils, could improve crop output by a factor of 8. It has been reported that the population of free living nitrogen fixing bacteria increased around the charcoal buried in tropical soil. Probably a small amount of nitrogen seems to accumulate into soils by charcoal application as is also the case in slash burn cultivation.

Charcoal has also the capacity to neutralize the impact of acid rains on agricultural soils.

THE FEASIBILITY OF ON FARM CHARCOAL PRODUCTION IN INDIA

Although charcoal application to India’s soils would bring about significant improvements in crop out put, it is very unlikely that the Terra Preta technology has any chance of becoming rapidly and widely adopted. The major problem is the availability of wood or woody biomass for charring. Most of the available biomass difficult to compost is used as fire wood. Even crop residues that should be composted are also,unfortunately enough, used as fuel. Cotton and pigeon pea stalks and other farm crop residues that are difficult to compost could form a source for making charcoal if other sources of fuel are available. The few sources likely to be available for charring are rice and peanut husk, decorticated corn cobs, husks from tender coconuts or Palmyra fruits. When rice husk is lit it smolders but does not really burn, it gets charred. The proper charring of rice husk plus it’s charging with urine could be the way for rice farmers. With the excessive application of rice husk charcoal - because of high concentration of potassium and the higher pH than wood charcoal- browning of leaves could result.

There are a number of other possible sources as well.

Prosopis juliflora is a thorny tree growing wild on fallow lands, gullies, roadsides etc. The stem and bigger branchesarethe primary source for commercial charcoal. But masses of side branches, too small for traditional charcoal making are easily available.

Ipomea carnea grows in thick stands in water bodies and produces huge amounts of semi woody material. These and other possible sources of semi woody material such as lantana (Lantana camara) or eupatorium (Eupatorium odoratum) can cheaply be collected for making charcoal in a very simple way.

PEBBLEGARDEN

Pebblegarden is an effort to regenerate severely eroded lateritic wastelands in Auroville, T.N. using home and neighbourhood resources.

At Pebblegarden, for 10 year now, we have been working with charcoal as an amendment to enhance and maintain soil fertility. The results have been very promising indicating better plant growth, better plant health and better yields. Pot experiments have shown clear results in favour of charcoal application. One small field experiment has shown a 40 % increase in biomass production in plots treated with powdered charcoal inoculated with EM versus control.

The inspiration to work with charcoal came from various sources. Our reflections are based on the study of similar practices like raab, the available materials, film, books and web and personal experience. (6)

However the main source of inspiration for using charcoal came from the discovery of Terra Preta do Indio in the Amazon rain forest.

WORKING on Terra Preta AT PEBBLEGARDEN

Our approach to Terra Preta all these years has been mainly empirical. Just like all other gardeners, we know our garden well enough to figure out if something works or not. We have been following the practices described hereon half an acre and have found a considerable improvement in the performance of the garden.

Making charcoal

There are very simple ways of making charcoal. Here, at first dry branches were collected and just tossed in a heap. Fire was set to the heap and allowed to burn until the high flames came down, after which the fire was extinguished by pouring plenty of water on it (sand or soil can also be used for that purpose) and charcoalis obtained. Next, we also burned odd shaped log-left over pieces from the saw mill. We let them burn for some time, poured water on the glowing fire and scraped the charred layer off and repeated the procedure. The obtained charcoal was then dried in the sun.

At present we use a kiln called the Iwasaki kiln, made from old oil barrels. An important advantage of making charcoal in a drum rather then in the simple or traditional way is the possibility of obtaining wood vinegar (7). Wood vinegar is obtained by condensing the smoke during the charring process. Wood vinegar is an excellent pro-biotic agent either as plant health promoter or soil conditioner. It has been recognized since 1960s that the wood vinegars extracted from broad leaved trees are more efficient for the growth and rooting of various plants than that of conifers.

A drum kiln and distillation pipe can be made in any rural metal workshop. The cost of such a device should fall within the financial capacity of a very large section of Indian farmers (8).

Charging the charcoal

Charcoal needs to be charged before applying it to the soil. This could probably be done in many different ways. We are working with human urine, EM and EM bokashi, 10 % water-wood vinegar solution, vermiwash and vermicompost.In the process of compost making, the more charcoal is used, the faster the decomposition-Exothermic reaction- progresses. Under aerobic conditions the Bacillus group seems to become dominant and produces antibiotics. It has been reported that these antibiotics inhibited the growth of some soil born pathogens, Pythium, Rhizoctonia, Phytophtra and Fusarium and were effective to suppress root diseases of various plants.

Our usual procedure though is crushing the charcoal into particles of about 1 cm2, saturating it with human urine and keeping it overnight. There is very little or no smell detectable as the nitrogen and minerals contained in the urine get absorbed into the charcoal pores. The soaked charcoal is then mixed with vermicompost and EM bokashi and kept in a drum for fermenting for a few days. This mix is spread 1 inch thick on vegetable bed and incorporated.

One measured and controlled experiment has shown a 40 % increase in biomass production.

However the addition to the garden soil of charcoal only does not make for Terra Preta. Hence we also experiment with other ingredients found in Terra Preta such as pot shards, bone meal, rock dust and mulch which tend to be missed out by exegetes.

Overlooked ingredients in Terra Preta

Potshards.

Not so long ago in South India people were cooking food in earthen -terra cota- pots. Once a year at the harvest festival all the old pots were thrown away and broken. For preparing the festive meal with the fresh produce from the new harvest new pots were used so to obtain the best taste. The old pots were thrown on a heap or just discarded in a haphazard way.

There is no reason to suppose that the Amazonians would have acted in any way different to the people of South India. Because wherever Terra Preta is found one finds equally potshards. These can make up 8% of the total soil mass. However the pictures clearly show that the pots were not just thrown away on a heap; rather they seem to have been deliberately used in the elaboration of the Terra Preta soils. It is even mentioned that pottery was made with the only purposeto incorporate them into the soil. The potshards consists of baked silica clay mixed with various other elements. The dynamic exchange between silica and carbon is supposed to be pivotal for the appearance and construction of life on the planet. Research by Jeanne Rousseau has shown that the bio-magnetic exchange between carbon and silica radiates at the same wavelength as living molecules. One can infer that an electro magnetic exchange occurs between charcoal and silica-clay.

Research has shown that the ceramic potshards found in Terra Preta contain sand, (amorphous silica) feldspar and iron oxides. The abundance of feldspar, coarse igneous rock (Granites, Rhyolites and Quartz) suggests the crushing of rocks found near the banks of the rivers for incorporation in the clay substrate. Extracts from medicinal plants have also been detected in the kaolin clay matrix.

These rock elements are most likely paramagnetic. It can thus be inferred that the potshards could be paramagnetic. Paramagnetic volcanic soils are known to be very fertile. In his book on paramagnetism, Philip Callahan reports that soils in which plant growth is perfect are mostly paramagnetic in nature.

Thus pottery must be considered as an important and therefore an integral part as much as is charcoal, in the whole process of the Terra Pretacreation.