[Terrapreta] The Science of Terra Preta Formation

[Sean K. Barry]

Hi Philip,

Thanks Philip.  This looks like fertile ground for reading about the topic under discussion.

...
The chemical structure of BC is highly aromatic (Schmidt and Noack, 2000<http://soil.scijournals.org/cgi/content/full/70/5/1719#BIB44>), yet the possibility of abiotic and microbial oxidation, and the formation of functional groups with net negative charge on BC particle surfaces cannot be ruled out (Schmidt et al., 2002<http://soil.scijournals.org/cgi/content/full/70/5/1719#BIB46>). For example, charred plants showed large amounts of extractable humic and fulvic acids with high concentrations of carboxylic groups after oxidative degradation with dilute HNO3 (Trompowsky et al., 2005<http://soil.scijournals.org/cgi/content/full/70/5/1719#BIB56>). 
...

Above from that paper, the authors say that VOC (volatile organic compounds, aromatics, VM, carboxyl groups, etc) found on the surfaces of Black Carbon (BC) particles have lots of negatively charged sites ... like what are found in humic acids.  And then, humic and fulvic acids are found on charred plants.  That's interesting.  These acids are supposedly why compost increases CEC.  I think this paper clearly shows in at least one way that charcoal ALONE (or it and the VM on charcoal) can increases CEC in soils that contain it.

But it is done by juxtaposing highly weathered kaolinite soils, with and without BC, though.  That native Anthrosol soil alone has low OM and very low CEC to begin with.  Anything organically sourced is going to increase CEC, right?  Now what about in temperate soils, that maybe do not have CEC deficits of tropical soils and/or perhaps different base saturations?  Would charcoal improve CEC in soil that had been inundated with ocean water (Na saturation)?

I don't know if the paper addresses any time frame for effective improvement in CEC from BC?  How long can BC maintain an increase in CEC in the soil?  Does the effect "wear out" over some time frame?  Does it require continued applications?  It's 2 meters deep in some places in Amazonia, with pottery shards and charcoal bits the whole way down.

I suppose it is possible to use charcoal (BC) as a tool in managing CEC in soils, along with other nutrient management, perhaps.
Can charcoal-in-soil be in anyway therapy for certain types of degraded soil?  Can it help fix the fertility problems in salty, alkaline, acidic, arid, over-farmed, or poorly irrigated soils?  Can charcoal be brought into a mixture with other soil amendments that together can balance
problems in a soil, fix the CEC and base saturation, and make it more productive for plant growth?  Is there charcoal in a specific recipes for most problem soils?

Regards,

SKB
  ----- Original Message ----- 
  From: Philip Small<mailto:psmall2008 at landprofile.com> 
  To: Terrapreta at bioenergylists.org<mailto:Terrapreta at bioenergylists.org> 
  Sent: Sunday, April 06, 2008 7:53 PM
  Subject: Re: [Terrapreta] The Science of Terra Preta Formation




          ----- 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



          There is no evidence that char does provide cation exchange...

  Char increases CEC, but it takes time for the biogeochemistry to work.  The BC surface must oxidize. 
  See "Black Carbon Increases Cation Exchange Capacity in Soils<http://soil.scijournals.org/cgi/content/full/70/5/1719>" published in SSSAJ, 2006.

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