[Terrapreta] Soil Food Web

[Philip Small]

Appreciate that observation. That makes sense to expect a short term
reduction in CEC, followed by a significant increase on the back end.
Assuming this is the case, the time it takes to get through that trough can
be managed: supplemental N source added with char as high C/N soils tend to
lose C when shocked/stimulated, condition the char before adding it to the
soil, opt for smaller incremental additions of char, place the char deeper
in the soil profile than the bulk of the humus, etc.

In some situations, increasing CEC without also immediately adding the
cations to populate that increased exchange capacity could be asking for
soil trouble.  Elaine Ingham has made this point in her concerns with adding
charcoal to soil, and, whle she didn't go into detail, I see it as a valid
point. Increasing CEC in acidic soils could decrease base saturation and
increase aluminum toxicity, in sodic soils (and the related grass tetany
prone potassium affected soils caused by high manure applications) it could
exacerbate the imbalance of monovalent cations relative to divalent
cations.  Thus a measured increase in CEC, as occurs as char conditions in
the soil, could be a very good thing, giving the fixed mineral fraction time
to mineralize, and to feed a balanced supply of cations into the soil
solution. The more I learn from you folks about biochar, the more taken I am
by it. -phil

On Sat, May 10, 2008 at 6:29 AM, Jim Joyner <jimstoy at dtccom.net> wrote:

>  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
>
>
>
>  ------------------------------
>
> _______________________________________________
> Terrapreta mailing listTerrapreta at bioenergylists.orghttp://bioenergylists.org/mailman/listinfo/terrapreta_bioenergylists.orghttp://terrapreta.bioenergylists.orghttp://info.bioenergylists.org
>
>
>
> _______________________________________________
> Terrapreta mailing list
> Terrapreta at bioenergylists.org
> http://tech.groups.yahoo.com/group/biochar/
> http://terrapreta.bioenergylists.org
> http://info.bioenergylists.org
>



-- 
Philip Small, RPSS
Land Profile, Inc. * PO Box 2175 * Spokane, WA 99210
509-844-2944 cell * 509-838-4996 fax * 509-838-9860 office
Profile: http://www.linkedin.com/in/philipsmall
-------------- next part --------------
An HTML attachment was scrubbed...
URL: /attachments/20080510/f84c1371/attachment.html