Re: Advice on shredders
- To: M*@ucdavis.edu
- Subject: Re: Advice on shredders
- From: R* F* D*
- Date: Mon, 11 Oct 1999 23:56:03 -0400 (EDT)
At 06:44 PM 10/11/1999 +0100, you wrote:
>Tim, do you consider bark chips take away nitrogen, whether used as a soil
>lightener or in pots- I see it is used extensively mixed with other items
>in some proprietory mixes, for example, for cultivation of citrus in pots.
>Edward
Edward:
Wood is rich in cellulose, which can readily be broken down into sugar. The
part of the wood which gives it strength and durability is its lignin.
These materials are composed of polyphenols, which are much harder to break
down. Chemically, it is closer to coal with its greater abundance of carbon
as opposed to hydrogen and oxygen. Bark is much richer in lignin. I would
imagine that the more lignin there is in wood, the denser it is, and the
more insect- and weather-resistant it is.
In other words, the `spine' of hydrocarbon rings makes up a greater
proportion of the lignin molecule; cellulose, like starch, is a polysugar
and therefore a carbohydrate. These have a `molecule' of water for every
carbon (usually a hydrogen and a hydroxyl group), making it easier for
bioorganisms to extract chemical energy from it.
This means that the cellulose-rich portions will make an immediate nitrogen
demand (unless gotten to first by termites!), and the lignin will use
nitrogen at a much slower rate while it breaks down into humus. Shredded
bark not only is superior as a mulch, but it provides much more humus to
build up soils. Cellulose will leave behind very little residue after being
consumed. This is why quality mulch will have as little wood fiber in it as
possible.
In North Carolina, where there is a strong furniture industry, hardwood bark
mulch is available. This is ideal for my Salvias, which are native to
pine-oak forests in the mountainous tropics. This mulch is ideal also for
bramble fruit.
Richard F. Dufresne
313 Spur Road
Greensboro, NC 27406
336-674-3105
