[LottyLouis]

I've been reading that wood chip isn't too good for using as a mulch. Apparently it sucks nitrogen out of the soil and plants will suffer as a result. Better to let it rot in a heap, preferably mixed with horse manure. Whew! I was about to bury the lotty in a three foot blanket!
My question is...would sawdust be any better? Rot faster? Suck out less nitrogen? I'm guessing it depends on what wood the sawdust comes from...any comments?   

[Uzzy]

I have a colleague in my office who has mentioned this about mulch. It depends on which trees the mulch is from, a recent visit to Kew showed them using wood chipping as mulch and one assumes they know what they are on about.

[GrannieAnnie]

Conifer chippings are definitely not good, but they do sell commercial bark for mulching, so I agree, try to find out which wood is okay and which isn't.

[JayG]

It's true that wood contains little nitrogen, so the microorganisms which break it down have to 'borrow' it from their surroundings, although the loan is eventually paid back (with a little interest.)

If the sawdust is used as a mulch it can't 'suck' nitrogen from the underlying soil to any significant extent, so won't cause a problem unless you dig it in before it's rotted down.

Sawdust and chips will both tend to acidify the soil at least temporarily - sawdust more so than chips because it's finer and rots quicker, although the type of wood would also be a factor.

A thick layer of sawdust may not be the best thing to use as a mulch as it may compact down and prevent rain and air getting to the soil.

If adding to a compost heap both need added nitrogen to speed decomposition, but wood chips will still take a long time - sawdust would also need to be mixed with other materials to stop it becoming soggy, compacted and airless.

[Dave NE]

I have an on going experiment with sawdust. Last November I filled a large wheelie bin with sawdust and mixed in lots of urine (nitrogen), nothing much happened over the months but the level did drop about 12 inches, I have added horse muck and just lately coffee grounds to try and speed up the process, it should turn out as fine compost, just a matter of when, Dave

[JimB]

.

If you were to read any of the old gardening books, sawdust or wood shavings was a big no no!

Bark chippings then had not been invented.

It was only when peat was deemed a no no by a section of the gardening press etc, that  the commercial compost makers tried to convince the gullible that wood shavings and bark were acceptable in their composts, even though they are rubbish!