[Terrapreta] Soil Food Web

[Sean K. Barry]

Hi Jim,

...  an investment requiring a return. 

Yes, Jim, I've long thought this.  That carbon-into-soil should be considered as an investment, with accruing long term benefits that will be returned as long as the carbon remains in the soil.  Considering the recalcitrant capacityof charcoal in soil"carbon bank"  may hold and deliver economic benefits that far exceed the initial investment cost required to put it into place.  I don't think the value of the charcoal-in-soil has been measured by modern humans or even by the Indios in this way.

The caveat (and my belated point) is, given the additional "activity of soil microbes in  the soil", that only adding charcoal without adding or growing other OM might lead to a reduction in humus and a commensurate reduction in CEC.

I think this is what Dr. Christoph Steiner discovered this, too.  This observation could also play into the supposed reproductive nature of Terra Preta soils.  The continuous re-introduction of new biomass is required to make the returns.  Maybe charcoal can speed self-composting or something like that.  That is what this Dr. Wardle paper was saying.  The charcoal is acting merely as a catalyst of sorts to bloom microbial activity and increase the production of humus into the soil by the more rapid degradation (by more microbes) of in-falling plant debris.  Some food diets for people talk about turning our bodies in fat burning/fat metabolizing furnaces.  Charcoal could be part of a soil diet to make it into "plant-fall metabolizing" furnace that leaves humus in the soil.

Turning biomass is into compost, converting biomass into charcoal, or when these are mixed never results in all of the carbon inputs remaining out of the atmosphere, but it does increase carbon in the soil over that which was there before.  And it will do this every time it's done.  You can't "fill" a carbon bank", it seems, not any more than a beaver can "fill" a beaver dam.

Regards,

SKB

  ----- Original Message ----- 
  From: Jim Joyner<mailto:jimstoy at dtccom.net> 
  To: terra preta<mailto:Terrapreta at bioenergylists.org> 
  Sent: Saturday, May 10, 2008 8:29 AM
  Subject: Re: [Terrapreta] Soil Food Web


  Sean K. Barry wrote:

  Charcoal carbon, when added to soil does appear to increase the growth in populations of soil microbes and the activity of soil microbes in the soil, leading to an increase in soil organic matter, and hence an increase in CEC.

  Sean,

  You raise an interesting implied point. While I think your statement is true, it may be critical to see just how that works. The added OM that is broken down into humus must come from someplace. It might come from compost or cover cropping, or it might even come from just the growing of crops. Economics is likely to determine how the addition comes about. 

  Personally, I use no-till with cover cropping and rotations to achieve an optimum level of CEC/humus. (Composts work better but not cost effective for me -- the humus can be greater but the benefits don't justify the costs.) My hope is that the addition of charcoal will elevate that level of CEC/humus with no additional costs (beyond the charcoal introduction), hence, increasing the productivity of my soils. I am also hoping the benefit of charcoal is permanent. If that is true then, the charcoal becomes not a cost but an investment requiring a return. One could then consider the charcoal a part of the real property. But I digress . . .

  The caveat (and my belated point) is, given the additional "activity of soil microbes in  the soil", that only adding charcoal without adding or growing other OM might lead to a reduction in humus and a commensurate reduction in CEC.

  Jim

    Hi Larry,

    You say:
    when charcoal with it's pore spaces are occupied with microbes and when charcoal, consisting of carbon binding sites for nutrient ions, is used then the structure, charcoal, hosts the functions of microbes, fungi, roots and nutrients.

    I like yours and Tony's comments on structure.  The corral reef is an apt analogy to biochar in soil.  It is just a physical thing, though.  There is NO chemical use by organisms on coral reefs of the calcium carbonate in coral reefs.  If there was, then the reef would disappear.  I don't think that charcoal itself interacts chemically with microbes or the nutrient ions in soils, either.  The charcoal has physical impacts on the soil structure (greatly increased "enclosed" surface area I suspect is the greatest addition), but it is not chemically active, per se.

    CEC in soil is generally increased by the addition of soil organic matter and by some clays which both do have more "binding sites" for cations of nutrients like Calcium and Potassium, etc.  The number of "binding sites" (negatively charge sites attracting positively charged cations) is measured in Million equivalents per gram Meq/g, meaning the number of millions of negative charges per gram of the soil.  Charcoal carbon does not have high numbers of negative charges on its surface and so does not increase CEC directly when it is added to soils.

    Charcoal carbon, when added to soil does appear to increase the growth in populations of soil microbes and the activity of soil microbes in the soil, leading to an increase in soil organic matter, and hence an increase in CEC.

    Regards,

    SKB

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