[Terrapreta] Effect of Washing Charcoal

[Richard Haard]

Philip we had no change in pH with our block study, with two types of  
charcoal . Our charcoal home made had high ash content.

Buffering properties of soil comes into play in the explanation.  
Typical result is pH 5.4, buffer pH 6.2  - no correlation of pH with  
treatment.

I think the potential for pH change by charcoal in soil addition needs  
to be qualified.

Our pH is getting a bit high for our native plants and we are  
contemplating a sulphur treatment. Linked to this we would like to  
apply rock phosphate as sulphur treatment releases P to plants. I  
wonder if this combination with charcoal might be a good practice?



Rich
On Jun 27, 2008, at 12:00 AM, Michael Bailes wrote:

> I managed to kill some acid loving plants with pyrolysis charcoal  
> from rice hulls and other sources.
> (I stole it from BEST)
> Perhaps traditional charcoal would have ash which would raise pH
> The phrase "Lowered soil acidity", is a little ambiguous.
> Does it mean pH goes up or down?
>
> Rarely people test the char- or soil- before they add char to soil/  
> potting mix etc.
>
> I am not even sure if I know what pH means any more.
> The more I learn about soil science the more confused I get.
> m
>
> 2008/6/27 Philip Small <psmall2008 at landprofile.com>:
> 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
> 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. Calcium carbonate equivalent (CCE) 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, 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.
>
>
> -- 
> Michael
> Most gods throw dice, but Fate plays chess,
> and you don't find out til too late that he's been playing with two  
> queens all along.
> Terry Pratchett
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