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  • From: Toby Hemenway <hemenway@jeffnet.org>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] Tree legumes
  • Date: Thu, 3 Apr 2003 21:17:32 -0800



I am interested to know your opinions on tree and plant legumes in terms of
when they release N.

I figured someone else would grab this; I'm kinda busy so I'll do it from memory rather than unearthing the citations. Radio-isotope (N) studies show that with tree and shrub legumes, very little N makes it into the soil (out of the nodules) until coppicing or cutting. A small percentage enters via leaf litter without coppicing within the first 6 months of labelling, but not much (enough to make a difference? Dunno). But after coppicing, the roots and nodules die back, and there's a very large flush of N into the soil. Seems to me there are data on alfalfa in Nyle Brady's "Nature and Properties of Soils" showing the same thing: at harvest, the roots pump N into soil, but not too much before harvest.

Toby
_____________________________________________
For a look at my book on ecological gardening,
Gaia's Garden: A Guide to Home-Scale Permaculture, visit
http://www.chelseagreen.com/Garden/GaiasGarden.htm


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