[permaculture] N-starvation and mulch
Toby Hemenway
toby at patternliteracy.com
Mon Oct 29 00:41:45 EDT 2007
Paul Cereghino wrote:
> Second could be bioturbation... worms or other thingies pulling woody
> material down into the soil creating local low N spots?
That's a likely one--carbon moving down rather than N moving up. Thanks!
> It seems like there is a
> need to align your mulch approach and your target community composition.
I think so, too. Elaine Ingham and others have done a lot of work
showing that non-woody plants (veggies, grasses) live in and prefer
bacterially dominated soils, and those can be created using mulches and
composts from non-woody tissue. (makes sense, yes?) Tree crops prefer
fungal-dominated soils, which derive from woody tissue. Fungi are much
better at breaking down wood than bacteria.
I use a lot of woody mulches simply because wood is a readily available
resource here--the timber industry, but more locally, city arborists and
the electric company generate tons of it for free. I try to get fresh
stuff with lots of green leaves and young green twigs in it to give me a
lot of nitrogen and so it will start composting quickly. I hypothesize,
or maybe just delude myself, that with more green stuff in it, more
bacteria will grow than in straight woody mulch, and thus help my
vegetables. This year I've got a lot of straw leftover from a straw/clay
sauna and heated cob bench we built, so I'll see if there is a
difference due to the different mulches.
And I agree with Dieter, Keith, and all that the mulch does start
decomposing almost instantly, with lots of critters moving back and
forth between soil and mulch. You don't see hyphae in the mulch right
off, but it doesn't take long before you do. And as William Albrecht
says, "microbes dine at the first table," so there's probably a period
after decomposition starts where N in the mulch is cylcing among the
soil life and not really getting to the plants until the soil life
settles down a bit.
Toby
http://patternliteracy.com
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