[Terrapreta] The Science of Terra Preta Formation

[Greg and April]

Does not the reports from Glaser et al. (1998 and 2003) and Brodowski et al. (2005) have any merit?    They specifically state that " formation of condensed aromatic structures depends on the manufacture of charcoal ". 

In which case you can increase the exchange potential, by the addition of char with these compounds, and not just due to different particle size.


Do you have any documentation that show's / suggests that fired clay can not change the soil cation exchange potential, in any way?    

One major company disagrees with you - even to the point that they are marketing a product, in the form of fired clay intended to raise the CEC of aquarium gravel.

What if the fired clay is inclined to act as a receptor for different ions, than the local unfired clay?    Even if in minute quantities, it could be enough to ensure that long term collection of key trace minerals makes a given piece of land more productive than another piece of land 50-100 yards away.



I have never stated in any way, that I thought that the shards did more than assist in the beginning of the formation of TP.    

I think the char is catalytic in nature, increasing the potential of the local soil.    Further, I think that the shards, do not really contribute to the current soil ( TP ), but, were instrumental in getting it established - wither this was accidental or on purpose, I don't know - perhaps it was accidental at first, but later on?    Who knows.    Just how it did it's job, is very much open for debate.


Greg H. 

  ----- Original Message ----- 
  From: Jim Joyner 
  To: Terra Preta 
  Sent: Sunday, April 06, 2008 15:31
  Subject: Re: [Terrapreta] The Science of Terra Preta Formation


  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 )
    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 ).    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 
      To: Greg and April 
      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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