[Terrapreta] Praire is natures way of making terra preta.

[Sean K. Barry]

Hi Tom,

Good question, Tom.  I have wondered, too, about really how much charcoal is left on soil when there is an "open-air" burn of the plants on top of it?  One day, I was pondering about how the Amazonian's were able to start a burn and have it charred, rather than burn?  My next thought from "how to quench a fire" came as "it rains in the Amazon every day".  I wonder if anyone has studied how much carbon you can pile up on the soil, if you get a the fire re-started just when it has stopped raining, and then later in the day, rain puts the fire out again?  Then, do that every day?

Your story about machine burning the residues from seed grass harvesting is very interesting.  Do you think it shows that there is hardly enough biomass on grassland to consider making char out of it, because you would have to repeat the process every year?
Maybe this is part of why the Amazonian's succeeded so well with TP?   Was it because they were in a jungle with 350' hardwoods standing above it, containing an enormous tonnage of standing biomass ?

Kevin, Bob, Jon, ... No, I don't know for an absolute fact that there was not a jungle in South America 2500 years ago.  But, I think that maybe there was, for whatever that's worth.

"Where is the data?"  You're thrust for us to focus on the scientific rigor is refreshing, Tom.

Regards,

SKB
  ----- Original Message ----- 
  From: Tom Miles<mailto:tmiles at trmiles.com> 
  To: Terrapreta at bioenergylists.org<mailto:Terrapreta at bioenergylists.org> 
  Sent: Saturday, September 01, 2007 11:19 AM
  Subject: Re: [Terrapreta] Praire is natures way of making terra preta.


  Where is the data?

   

  Before you jump to too many conclusions someone should do a full literature search on this topic. I found several references on biochar and prairie fires when I was doing an internet search a few months ago. I do not have access to some key academic databases in soil science but I found that there has been work on prairie fires and the role of the resulting carbon in soil fertility.  If I remember correctly they concluded that fire stimulated growth in grasses partly due to thermal shock, partly due to the elimination of residues and competing grasses, partly due to nutrients in the burned residue,  and only secondarily due to carbon accumulation. It was calculated that he amount of carbon from burning contributed little to soil organic carbon and long term accumulation. The concentration of inorganic elements that results from burning stimulated growth for the first year but the effects were not lasting. Similar studies have been done for rice straw.

   

  We saw these effects in the 1970s when we burned hundreds of acres using field burning machines that we designed. We used to burn the residues from our grass seed harvest In our Willamette Valley. Annual burning of more than 300,000 acres resulted in production of high purity seed and elimination of volunteer plants and diseases. We designed and tested machines to control combustion of the residue. We machine burned hundreds of acres on many different grasses. Fossil fuel was only used to run the tractor and a fan on the machine, The residue sustained it's own fire. Burnout was good. Char left on the ground was not measured but it was probably more than open burning because we released less to the atmosphere. Emissions were very good. Most of the nutrients returned to the soil rather than put into the atmosphere. Political pressure changed the regulations and reduced  burning to less than 10% of the total acreage. It is used sparingly now for select fields. In some areas more straw is returned to the soil which has improved tilth and water use. Seed varieties have also changed with the market so we now grow less annual and more perennial grasses.

   

  Tom Miles

           

   

   

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