[Terrapreta] TP origins

[Ron Larson]

Tony (cc terra preta list members):

    I answer your message today (below) because I am an electrical engineer with a combined past and current interest in terra preta, lightning, and pyrolysis (and almost zero knowledge of soils and biomass grwoth).  I find your suggestion quite interesting and plausible.

    What I want to explore a bit more is why there was apparently a 70 year delay between the (presumably lightning-caused) fire and the beginning of apparently greatly improved soils.  That is, you report the soil didn't look at all good 20 years ago but put the presumed cause at 100 years.  I don't remember ever reading about this in the lightning area, but I wasn't looking for this sort of topic when I stopped doing lightning work 10 years ago.   I can probably do a literature search without too much difficulty (there are annual lightning conferences) - but certainly expect to read that people have reported lingering fires (I have even put one out in a stump after about a two-day lapse).  But over a large area is a different story.  In the case of Brazil, I doubt this is the explanation, where (maybe) the boundaries are square, the sites are mainly along rivers, etc.  It could be an explanation (like pottery production) that caused natives to start doing more aggressively.

    Given my limited soils knowledge, I can imagine time delays, but not a big change over 20 years after a 70-year hiatus.  One possible answer is that there was a second fire closer to 20 years ago.  Another is that soil improvement couldn't begin until the grove was cut down. I wonder if you or anyone could explain this timing issue.  

Ron

  ----- Original Message ----- 
  From: Janice Stettler 
  To: Terrapreta at bioenergylists.org 
  Sent: Wednesday, May 23, 2007 11:55 AM
  Subject: [Terrapreta] TP origins



  To all:

  Please consider my humble theory for the discovery of the TP process   My half-acre garden is sited on a hilltop that once sported a dense stand of Douglas fir (which I used to build my house).  When the stumps were removed, it left five inches of poor topsoil over a clay hardpan base, which is typical for glacial scouring.  Twenty years later, my top soil layer is about a foot deep (deeper in spots) and everyone who sees my soil is surprised at how rich and dark it is.  Until recently I've taken credit for the transformation--green manure crops, compost, etc..  However sitting atop that hardpan is a scattering of charcoal nuggets that I failed until recently to see the significance of.  Approximately ninety  to a hundred years ago, based on the fire scar on some of my older trees, there was a brush fire that swept across my land.  Slash burns in forested land frequently produce underground fires that smolder for days, feeding on ancient intact root systems without above ground stumps to suggest their existence--a natural charcoal kiln.  Therefore though I'd like to take credit for the growth of my top soil, I am inclined to think now that I've been witnessing a diluted version of Terrapreta soil growth due to the natural event of sub-surface charcoal production that had simply been dormant under forest shade.  It's easy for me to imagine the possibility that the "ancients" were capable of observing over time, what I was blind to until recently.  Certainly in a climate that permits year round cultivation because of temperature and moisture availability, I would expect that TP process to be accelerated beyond what I might observe in Washington's coastal temperate climate.


  Tony Stettler




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