Query re onions, garlic & weeds

[zazen999]

Sawdust will take an awful lot out of the soil as it breaks down - it's really high in carbon and will use a load of nitrogen to decompose - might be ok if you are planning to take the mulch away but I wouldn't dig it in if it was me - could really upset the soil for years

Not if it is used as a mulch, it doesn't.

[King Carrot]

Hi King Carrot, you sound like an expert in such matters. The nitrogen which is used to decompose the carbon, is it taken from the air or from the soil?

I'm not an expert - just read a few things along the way to trying to get a healthy and productive soil - if sawdust is in contact with the soil it will use nitrogen in the soil during its decomposition making less available to any veg. One article I just read said aged sawdust is perfect as a mulch as long as you add nitrogen to the topsoil.

http://clic.cses.vt.edu/icomanth/27-Mulching.pdf

It'sthe first article that came up for me - I've not read it all and I'm not saying its gospel - if you want to know more - google the subject and read on