This is true due to the fact that woodchips use up some nitrogen as they
rot. Same with sawdust. One the surface, the effect is fairly minimal.
Mixed into the soil, the effect is more pronounced.

Since woodchips and sawdust have little nutrition to contribute, and deplete
nitrogen, there is little benefit for most folks in mixing them into the
soil as organic matter if the wood product hasn't been previously composted.
They are better used as mulch in the uncomposted state.

If you are making an effort to keep your soil in good condition, the chips
or sawdust shouldn't hurt anything. You may pick up some acid as the
tannins are washed out of the wood by the rain, but that may be desirable in
some situations.


"Victoria Clare" wrote in message
.217...
"emuir" wrote in
:

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?


I was just reading up on how to care for my new Christmas blueberry bush
and find that a mulch of sawdust is recommended for these, as it
apparently
helps keep up the acid levels in the soil. From this I would guess that
it
might also be suitable for rhodos or azaleas and other acid-lovers if you
have those.

I do have a bed where I have used sawdust for mulching under a mature
conifer, but I've used such a mix of components in that mulch (newspaper,
turf, rabbit droppings, weeds, prunings, lawn mowings, horse manure, part-
rotted compost...) that I can't honestly say what part the sawdust played
in the whole process. Worked though!

--
Victoria Clare
gardening high up in South East Cornwall
http://www.clareassoc.co.uk/
--