[Terrapreta] The Science of Terra Preta Formation

[Sean K. Barry]

Hi Lou,

I think that is a super question!  Do fired pottery shards in the soil play a completely different role than a bio-geo-chemical role?  Maybe the fired pottery shards are just harder and change the mechanical stability or the soil, preventing run-off?  Does the heavy rainfall wash away soil from around TP mounds containing shards?  Are TP soil formations in low-lying areas, ravines and etc., and are not washed out like other ravines?

No crock-of-... I mean chamber pot of human offal hypothesis here.  It's just rock-like pottery shards don't let the nutrient holding charcoal wash away.

Regards,

SKB

  ----- Original Message ----- 
  From: lou gold<mailto:lou.gold at gmail.com> 
  To: Jim Joyner<mailto:jimstoy at dtccom.net> 
  Cc: Terra Preta<mailto:terrapreta at bioenergylists.org> 
  Sent: Sunday, April 06, 2008 3:45 PM
  Subject: Re: [Terrapreta] The Science of Terra Preta Formation


  To All,

  As I follow the discussion, it seems mostly about chemistry,

  How about structure? Heavy rains leach and compact soils. 
  How might pottery shards change this?

  Just wondering...

  lou



  On Sun, Apr 6, 2008 at 6:31 PM, Jim Joyner <jimstoy at dtccom.net<mailto:jimstoy at dtccom.net>> wrote:

    Greg,

    Adding clay to a sandy or silty soil will increase the CEC because the average size particle is changed -- there are more electrical charges per cm3. Adding char to soil does not increase CEC. Ask Richard, he's done it. So far, it is only hoped that adding char to soil will foster an environment that will maintain the carbon in organic matter in order to increase CEC.

    Most, if not all, of the soils where TP is found are clay. Clay is defined by particle size. And it is these number of particles in a given volume of soil that will greatly determine CEC. Carbon can also increase CEC, the carbon in OM, but this will go away with heat and humidity.

    Whatever clay found in pottery, even if it were pulverized into dust, is very unlikely to increase the CEC from its native level. It would have to be a clay with a higher CEC (you say it is not) to do so and it would require huge quantities. The shards are obviously not pulverized and the contribution to the volume of soil would still be insignificant no matter what it contains.

    As far as the other elements found in the clay in the shards, they are likely to be minute and would have little or no effect on CEC in any event. If you add a supplement of trace elements (Planters II, e.g.) to your garden, it may make your plants grow better, which may increase the OM in your soil, which may indirectly improve CEC, but it will have no immediate effect on a soil test for CEC nor is it likely to change what is in the cation base saturation (I know, I've done it). 

    Jim

    Greg and April wrote: 
      Hmmmm.....

      I would have to disagree.


      With reports that char - especially a char produced at high temperatures, can be used in a battery, tells us that ion exchange can/does occur.

      From Wiki ( http://en.wikipedia.org/wiki/Terra_preta<http://en.wikipedia.org/wiki/Terra_preta> )
      Glaser et al. (1998 and 2003) and Brodowski et al. (2005) have proved that the formation of condensed aromatic structures depends on the manufacture of charcoal. It is the slow oxydation of charcoal that creates carboxylic groups; these increase the cations exchange capacity in the soil. 

      It sounds like you are saying that solid material can not remain if it is acting as an ion exchange site.    If this is the case, I disagree.

      I own a Roman coin, that dates from around 200 AD - and while it is heavily tarnished, and one can barely make out the design on it ( actually only parts of the design ), one can not deny that ion exchange has been occurring for hundreds of years ( almost 2000 years ), and still remain an object that can be handled and examined.

      Ion exchange materials come in many different forms, some of them long lasting some of them are not ( depending on the conditions ).    Clay is a cation material ( of greater or lesser potential depending on the type ), and firing it to pottery does little to change that.

      Kaolinite ( one of the materials found in the pottery shards ) has " a low cation exchange capacity (1-15 meq/100g.) " - ( http://en.wikipedia.org/wiki/Kaolin<http://en.wikipedia.org/wiki/Kaolin> ).    So while the exchange potential is low, it is still there.

      Other clay materials have variable amounts of cation exchange capacity - 

      Montmorillonite, has quite a bit of exchange potential, and was known in Central and South America ( we know the stuff as bentonite, and use it because of it's great cation exchange potential ) and Potassium and iron are common substitutes for it.


      Still, I like you, would like to know the source of the clay used to make the pottery in the first place.


      Greg H.


        ----- Original Message ----- 
        From: Jim Joyner<mailto:jimstoy at dtccom.net> 
        To: Greg and April<mailto:gregandapril at earthlink.net> 
        Sent: Sunday, April 06, 2008 12:50
        Subject: Re: [Terrapreta] The Science of Terra Preta Formation


        Greg and April wrote:

          The fact that the materials in the pottery shards, like that of char, will also provide cation exchange, can not be totally ignored.    
        Greg, 

        There is no evidence that char does provide cation exchange, if it did, the char would disappear with the OM. In fact, there is evidence to the contrary, that it does not directly increase CEC. Char seems to provide some kind of beneficial mechanical structure to soil but is inert itself -- that is why it is still there. 

        Similarly, the fact that the shard material is still there, tells us that it, like char, is not a component of the cation exchange and, I think, does not in any way electrically or chemically interact with the soil. 

        There is one possibility: that the aquarium material of which you speak provides trace elements. Maybe the trace elements in the shards is beneficial in some small way. Plants will do better with trace elements but soils around the world have long been leached of trace elements; It's ag product is not as nutritious but it still produces and people still eat the product. It's hard to believe that these shards are in any way a necessary component of TP. 

        I don't know the source of the clay in the pottery shards but I suspect it is the same clay that is in the soil, which would mean that what ever is in the shards is already in the soil. If they made the pottery from clay that was, say, from the mountains, might be a different story.

        Jim 

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