[Terrapreta] torrefied wood or charcoal?

[Jim Joyner]

Sean,

While agree with your conclusion, "torrefied is likely not as useful or 
effective in making an improvement to the soil as is low ash charcoal", 
I'm afraid your reasoning is based on faulty information.

Sean K. Barry wrote:  
> High ash content means higher pH. 
This may be true but not necessarily. If there is a proper amount of 
calcium and magnesium in the soil, the increased pH, mostly due to 
adding potassium in ash, will not persist long. It will wash out.
> This is not good for any soils unless they are very acidic to begin with.
Raising the pH of soil with ash (potassium), without regard to calcium 
and magnesium, will create brick. So, this would not be good, 
necessarily, for a acid  or any other soil.
> Raising the soil pH lowers the cation exchange capacity (CEC),
This is simply not true. You've got it backwards. CEC is not affected by 
pH. Ph may be affected by the things used to increase the CEC like clay 
particles (mostly silicates) or carbon (not charcoal). One typically 
adjusts soil calcium, magnesium and potassium according the CEC. Once 
that is done, pH will be slightly acid to neutral.

If charcoal in the soil raises CEC, it doesn't do it directly by 
addition. It may indeed create a habitat more conducive to the creation 
and holding of stable humus, which does increase CEC.
>  Higher pH is not a habitable environment for many soil 
> micro-organisms, either.
Just about everything that grows likes a pH of 6.8. But the addition of 
charcoal or torrified wood are unlikely to affect pH at all.

More importantly, pH is a boogey man. It's just a concept for measuring 
something that is rarely useful. A good, balanced soil will have a 
slightly acid ph. However, a soil that has a slightly acid soil will not 
necessarily grow anything. There are only nutrients and cations in 
active soil (I do not include charcoal as active -- it's virtue seems to 
be in its inactivity and crystalline structure). There are no pHs.

Having said all that, since many of the compounds in torrified wood can 
be acted upon by organic processes, my concern for adding torrified wood 
to soil would be that it would be much adding sawdust. It won't affect 
pH but it will tie up nitrogen, taking it from crops . . . for a long time.

Jim