[Terrapreta] Effect of Washing Charcoal

[Philip Small]

Re: [Terrapreta] list of benign effect
On Thu, Jun 26, 2008 at 2:05 PM, Michael Bailes <michaelangelica at gmail.com>
wrote:

>
> I am not sure about "Lowered soil acidity", that has not been my
> experience.


Alkalinity is a well established characteristic of charcoal.  The following
is from The Charcoal Vision: A Win–Win–Win Scenario for Simultaneously
Producing Bioenergy, Permanently Sequestering Carbon, while Improving Soil
and Water Quality <http://agron.scijournals.org/cgi/content/full/100/1/178>
*Importantly, charcoal is hypothesized to have several positive impacts on
soils (Glaser et al., 2002). First, charcoal is ...  Fourth, charcoal is a
liming agent that will help off set the acidifying effects of N fertilizers,
thereby reducing the need for liming. *[emphasis added]

Michael, was your charcoal washed prior to your use? If you soaked the char
and then tossed the soak water, this could help explain your experience.

Normally, adding charcoal raises soil pH (aka lowers soil acidity) and is
thus considered a liming material.  "Lime" and "liming material"  are
interchangeable terms for any material that will raise soil
pH<http://www.soils.wisc.edu/extension/shortcourse/New_course_materials/SOILPHANDLIMING.pdf>.
Calcium carbonate equivalent
(CCE<http://hubcap.clemson.edu/%7Eblpprt/bobweb/BOBWEB2.HTM>)
is a measure of liming ability relative to finely ground limestone.  Ash has
a CCE of between 50% and 100%, which is fairly high, higher than coarse
limestone.

It is the ash content of the charcoal that drives its
CCE<http://hubcap.clemson.edu/%7Eblpprt/bestwoodash.html>,
and even charcoal made to minimize ash content (by burning off as little of
the charcoal as is practical) will have a dry weight ash content starting at
about 3%. Less efficient processes, such as my home-made charcoal, probably
yields starting out at about 10% ash.  The alkaline constituents in ash have
a reputation of being fast acting on soil due to their high solubility in
water. Thus the CCE of charcoal is fairly easy to reduce with water
processing.  This is likely why Dr. Reddy is using washed charcoal to help
improve alkaline soils in
India<http://terrapreta.bioenergylists.org/Saibaskharalkaline>
.
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