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  • From: Keith Johnson <keithdj@mindspring.com>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] N-starvation and mulch
  • Date: Fri, 26 Oct 2007 23:34:25 -0400

Thank you Toby,
That was elegantly said, much better than I could have even though I wanted to reply along those lines.
I've personally been mulching with every kind of carbonaceous material I could lay hands on for 32 years and I've yet to see plants suffer from N deficiencies. In the case of already low-N soils or high demand from heavy feeders, extra N from urine, fish emulsion, manures, or compost supplied the shortfall.

In regard to hyphae crossing over from soil to mulch, I actually do see that quite regularly, though it may take a longer or shorter time to do so depending upon the material, humidity, temp, fungal type, etc.
Keith

Toby Hemenway wrote:
Robyn Francis wrote:
Mulches with a hard cellulose structure such as sawdust, wood chips,
eucalyptus leaves and pine needles have high N demands to break down. Some N
will be drawn from air but can also use up N from the top soil layer.
I'm having a hard time figuring out a mechanism for nitrogen to be drawn up more than a couple of millimeters, then across an interface, and into a fresh mulch layer.
Fungal hyphae can transport nutrients, but it would be unusual to have a fungus with intact mycelial strands that cross the interface, from nicely decomposed earth into rough woody mulch.

I've always understood that the only place there is N lockup with mulch is right at the mulch/soil interface. The mulch doesn't have much nitrogen in it to start with (400 to 1 C/N or so), so what happens in the mulch itself can't be called locking up, just absence.
I've never noticed N-starvation in wood-mulched plants (and I use woody mulch almost exclusively. Quite the contrary--plants love it. But like I say, I'll listen to an alternative explanation.

Toby
http://patternliteracy.com
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Keith Johnson
"Be fruitful and mulch apply."
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also Bloomington Permaculture Guild




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