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28-12-2002, 09:47 PM

(Nick Maclaren) wrote in message ...
In article ,
Beecrofter wrote:
"emuir" wrote in message ...
I'm told that putting green woodchips onto soil has the effect of drawing
out nutrients from the soil as they rot down. Does anybody know if they
same happens if sawdust from seasoned wood is added to soil. Has anybody
tried this to build up moisture retention in dry areas?

Sawdust has a carbon to nitrogen ratio of about 400-1 and it will tie
up nitrogen if mixed into the soil.
It makes a good mulch for blueberries when laid on the soil surface.
It makes a soft place to land when mixed with sand under
playsets/swingsets.
It ties up enough nitrogen to make a pile of grass clippings rot
without stinking.

Er, no. I don't know where all the pseudo-science about "greens",
"browns", "carbon", "nitrogen" and all that came from, but it really
doesn't describe what is going on. Your description of how to use it
is fine - it is the explanation that isn't.

Grass is not a high-nitrogen material, and the reason that grass
clippings make a slimy, smelly mess is because they compact into
a wet, ANAEROBIC lump. Longer, more mature grass does not do that
on a small scale. Sawdust is less compressible, less decomposable
and prevents the smell by maintaining aeration.

SOME nitrogen is used by the fungi (not usually bacteria) in breaking
down wood, as in sawdust, hedge clippings and so on, but it is all
returned as the fungi themselves are broken down by bacteria. This
is one cause of the deep green patch just inside the yellowish strip
in a fairy ring.

The only common high nitrogen materials in compost come from kitchen
waste, dead animals and when you throw out a pack of MATURE dried
peas, beans etc. Almost everything else is fairly low. And nothing
less than putting large lumps of meat or dead animals on the heap is
likely to change the decomposition to being one dominated by the
protein-reducing organisms - the odd pound or couple of dead rats is
neither here nor there.

This is an interesting thought but I don't get it. Do we agree "high
in nitrogen" ought to mean having an amount which is going to be
useful for growing?? In that case, how can grass, young plants etc not
be high in nitrogen? I mean, how can you need it to make some but not
get it if you break some?

Warwick Dumas

"If Adolf Hitler flew in today, they'd send a limousine anyway."
- the late Joe Strummer