2cents
Green Thumb
Posts: 616
Joined: Thu Jan 08, 2009 2:04 pm
Location: Ohio

sawdust vs wood chips

Why does saw dust and wood chips have a different carbon to nitrogen ratio?

Aren't they the same OM?
:?

cynthia_h
Super Green Thumb
Posts: 7501
Joined: Tue May 06, 2008 11:02 pm
Location: El Cerrito, CA

Where is the source for this? (I'm thinking that there *may be* a buried explanation at that source.)

Cynthia H.
Sunset Zone 17, USDA Zone 9

The Helpful Gardener
Mod
Posts: 7493
Joined: Tue Feb 10, 2004 2:17 am
Location: Colchester, CT

Different woods have different C/N ratios, so those are generalities to begin with. Deciduous trees are 500-600 while some conifers like cedars, can go as high as 1000. Plus aging can change things (sawdust aged a year is nearly half the C/N of fresh), and the form (sawdust vs. chip) may be responsible for faster deterioration, hence different ratios...

Greens to brown, about equal amounts...Nature doesn't overthink this...

HG
Scott Reil

TZ -OH6
Super Green Thumb
Posts: 2097
Joined: Fri Jul 25, 2008 11:27 pm
Location: Mid Ohio

Lumber/sawdust is made from dead heartwood, which is almost all lignocellulose, so C:N is up around 400:1 or more. Wood chips, on the other hand, are mainly from branches and contain the living part of the wood just under the bark and the living growing twig ends. Winter wood chips are even more nutritious because, trees store nutrients (pulled back from the leaves) in the twigs over winter for rapid spring growth-leafing-flowering, which is why trees can begin to leaf out before the ground warms up. Due to all the proteins in the living and stored fraction of the twigs, wood chips have C:N around 100:1 as long as the chipper isn't fed anything over 3" thick. Also, the lignin is not fully polymerized in the young branch wood (not so hard) and can be broken down more easily by fungi.

2cents
Green Thumb
Posts: 616
Joined: Thu Jan 08, 2009 2:04 pm
Location: Ohio

Cynthia, no time now, but I'll have to look closer at the source of the info.
TZ & HG, thanks for the input, you've opened my eyes to possible reasons. Sometimes I am just a bit thick and baffled, without an explanation or supporting documents from the source.

The Helpful Gardener
Mod
Posts: 7493
Joined: Tue Feb 10, 2004 2:17 am
Location: Colchester, CT

Of course, TZ. I should have thought of that...
:oops:
HG
Scott Reil

Return to “Composting Forum”