Monday, January 26, 2009

Pottery shards, Terra Preta, Soil

Regarding impact of Pottery shards in the soil there had been still several questions in my mind. I had been searching for pottery shards in the agricultural fields and most often I got to see some pottery shards in the field. Where ever agriculture was the main livelihood, high densities of populations existence, civilization at the helm and space was a constraint, innovations were adopted by humans, and such practices are sustainable even now.

The charcoal and pottery shards are the two most common by-products of human habitats.

Source of Charcoal and Pottery shards in parts of rural India.

 

Aspect

Charcoal

Pottery Shards / baked soil

  1.  

Cook stoves

Charcoal

Cooking pottery utensils

  1.  

Water storage

 

Pots

  1.  

Slash and burn

Charcoal (up to 50%)

Baked earth

  1.  

Seasonal crop residue burning

Charcoal

Baked earth

  1.  

Slash and burn of forest areas / bushes intentional

Charcoal

Baked earth

  1.  

Accidental forest fires

Charcoal

Baked earth

  1.  

Rural enterprises

 

 

  1.  

- Potters Kiln

Charcoal

Broken pottery shards

  1.  

- Black smiths place

Charcoal

 

  1.  

- Hotels

Charcoal

 

  1.  

Community kitchens (Schools / temples / etc.)

Charcoal

 

  1.  

Rituals / Cultural

 

 

  1.  

- Ceremonial pottery used for all cultural occasions and festivals

 

Pottery shards

  1.  

- Yagnas

Charcoal

Pots

  1.  

- Cultural Bonfires – during Holi / Sankranti festivals / etc.

Charcoal

Pots

  1.  

- Cremation grounds

Charcoal

Pots

  1.  

- Housing

 

Roof tiles replacement

  1.  

Toys

 

Clay toys and Pots



At least some charcoal / biochar along with ash was contributed by the people living in habitations in the past (see table above). The availability of the quantity of such by-product, ingenious use, management and development are the aspects still to be discovered. If charcoal / pottery shards did not occur in certain areas in spite of human settlements existence, than there must be some reason yet to be discovered. But both charcoal and pottery existence as a result of human activities was beyond history, so there is no reason why these things are not seen..

The fired pottery made up of clay is most popular. Still the poor people in rural villages in parts of India cook in the clay pots. The pots used for drinking water collection is most common, even today millions of pots are produced and used all over India every year, the usage would be more especially during summers. The evaporation of the water from the fine pores of the pot cool the water inside the pot. The temperature would be at least 5 deg centigrade less than the surrounding air temp. The cooling effects would be very high under less relative humidity conditions. The roofs made up of clay tiles also provide cool shelter, and very much useful in the tropics where temperatures are very high during summers. For majority of the main festivals pots or pottery items are used. From Birth to death, for all important occasions pottery items are used.
The water tanks / ponds silt is used for pottery. The organic carbon content of the clay collected from such water tanks / ponds has around 0.9%. Such clay is mixed with a little ash+charcoal powder from the kilns.
And sometimes for fire resistance quartz sand is also used along with ash. The availability of ponds / tanks and a stream for sand helps in development of pottery.
The pieces of broken pots are thrown in a Farm Yard Manure pit. During manure spreading pottery shards also reach the fields. With time the size of the pottery shards reduces due to breaking. Ultimately over years the pottery shards spread. It was observed that the density of occurrence of pottery shards varies from field to field.

Bricks Pieces made up of clay were also seen in the fields although in few numbers. This appearance could be due to two reasons. In the fields where density of the bricks were high, the possibility is that there could have been a bricks making kiln in the fields, secondly the chance is that the bricks from the demolished houses enter into the fields as dumps.

Traditional Practices - sustainability of agriculture 

In India the farmers still love charcoal and ash (source is from cook stoves, burning crop residue in the fields, and some times charcoal and ash from the Yagnas (a ritual performed for prosperity and good), potters kiln, etc.). They do apply silt from irrigation tanks, etc., and farm yard manure, which are traditional practices. All these practices are able to increase the soil carbon, increase in soil microbial activity and increased fertility of soils. One could even see all these activities even now in India. In spite of cultivation of the fields since hundreds of years (even since the times when TP was practiced in Amazon), but the soils are still useful. Except in the last 40 years, due to green revolution and application of complex fertilizers / pesticides and non continuation of the traditional sustainable practices (by some of the farmers), our lands are degraded, less productive and have turned into acidic / alkaline. The hypothesis is that if terra preta soils happened in Amazon basin, there is no reason why other civilizations around the world have not discovered similar properties of charcoal and adopted. There is still scope to study and understand from countries like India. Please see this link for certain evidences http://e-terrapreta.blogspot.com/ Please also see this study report on the composition of the silt from irrigation tanks, applied in parts of India. This practice has turned many fields into dark earths, farmers are happy and it is still practices in many parts of peninsular India. 

"Economic evaluation of sediments as a source of plant nutrients" www.ias.ac.in/currsci/oct252008/1042.pdf 

"The results indicate that the sediments deposited in the water tanks of Medak District provided significant amount of nutrients (N, P and K), were richer in organic C and microbial activity, and thus can act as fertilizer substitutes for crop production. Because loss of microbial diversity through erosion from fields is one of the important factors for land degradation, returning tank sediments rich in nutrients, organic C, microbial biomass C and microbial population would help in improving the microbial diversity and biological activity in farm soils, thereby improving soil quality and crop production. Owing to the large amount of organic C in tank sediments, application to agricultural fields would increase soil C. The feasibility of desilting operations and returning such huge amounts of sediments to agricultural fields was assessed by determining the sediment quality in terms of nutrients, organic carbon (C), biological properties and their economic value as a source of plant nutrients. Analysis of sediment samples showed an average of 720 mg nitrogen (N), 320 mg phosphorus (P), 310 mg potassium (K) and 9.1 g of organic C per kg of sediment." Sharing of this information is not to deviate from the Charcoal + amendments, which we recognize to mitigate ongoing global changes and challenges.

2 comments:

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