[Terrapreta] The Science of Terra Preta Formation

[Sean K. Barry]

Hi Jim, Greg,

I think charcoal amendments into soil increasing organic activity and soil organic matter, which then increases CEC.  Plus things like kaolinite and maybe bentonite clays (even as pottery?) are a known CEC increasing amendment for soils.  CEC is basically the number negatively charged activation sites on molecules in the soil, which will attract, hold onto (temporarily) and deliver positively charged cations to plants as soluble ions.

Increasing organic matter in the soil is important for CEC, because organic matter (now decaying in soil) is full of both the cations needed for life and the molecular anions and anions sites to attract, hold, and deliver cations to/from.  When the molecular anions and anion sites that attract them are also in mineral elements of the soil, then the soil will hold these cations too and have them more available when the roots of plants come looking for the cations.

The mineral based CEC of soils outlasts the CEC of decaying organic matter put into those soils.  Compost provides a shock of fertility and some temporary increase in soil organic matter.  But it does not last, as the plants take up the nutrients and the plant organic decays, gases off, or dissolves into the soil, to become part of new plants or leaches or washes away.  Gravity and sunshine move nutrients around, too.
Decaying organic matter is sometimes the only source of nitrogen when a plant cannot fix nitrogen into the soil and it is the only kind of plant around.

CEC is the measure of the number of exchange sites.  These sites do somewhat act, I think, as "catalyst sites" for the exchange of soluble cations from organic matter and other nutrient additions to the soil into uptake by the roots of plants.  

Regards,

SKB


  ----- Original Message ----- 
  From: Greg and April<mailto:gregandapril at earthlink.net> 
  To: Terra Preta<mailto:terrapreta at bioenergylists.org> 
  Sent: Sunday, April 06, 2008 2:15 PM
  Subject: Re: [Terrapreta] The Science of Terra Preta Formation


  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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