[Terrapreta] Black soil

[Greg and April]

There is a short section in the book Permaculture: A Designer's Manual by Bill Mollison ( sp? ), where they talk about speeding up that process.    They actually go and take a section bare lava field, go through with a crusher to break it up, then start trees in small individual holes across the field, mulching with nothing more than nut shell and compost.    Each tree was on an irrigation line and the took pic's a yrs apart and the trees looked fine.

It's his belief that it's not that lava is infertile, but that microorganisms just have not had a chance to break down the rock into useful plant nutrients, but by jump starting the process, you can actually start using the land by making pockets that microorganisms can get a foothold and move out from.

Greg H.

  ----- Original Message ----- 
  From: MFH 
  To: 'Richard Haard' ; 'Kevin Chisholm' 
  Cc: 'Philip Small' ; 'Terrapreta' 
  Sent: Tuesday, June 03, 2008 21:27
  Subject: Re: [Terrapreta] Black soil


  Thanks Richard, useful material.

   

  Seems only iron and humus relate to black soil. 

   

  Let me compare with the soils in the Gazelle Peninsular of PNG. The last major eruption (neglecting for the time being the 1994+ eruption) was in 1937. These were eruptions where vast volumes of gas and pumice are released in clouds that can rise thousands of metres, with the pumice eventually falling back to earth under the spreading cloud of debris. Basically, the '37 eruption covered a substantial area of fertile land with inert pumice to depths up to 5m. Most of the damage to houses and trees occurs because the pumice gets wet with rain, sets like concrete, more falls and gets wet, and eventually this is too much for a roof and the building collapses. It sticks on the leaves and branches of trees and palms, and these collapse leaving a central trunk.

   

  There were no deliberate attempts at rehabilitation of the soil. But it rained, and the winds blew some organic debris over the landscape, birds poo'd, and some dropped seeds that germinated. In about 10 years there was a reasonable vegetation cover and the beginning of a humus layer.

   

  10 years later this was supporting food gardens and copra and cocoa plantations. By 30 years there was a 200mm layer of dark brown fertile soil overlaying the almost-white and very porous pumice, and topped with a humus layer around 100-125mm. 

   
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