permaculture

[Toby Hemenway <hemenway@jeffnet.org>]

on 7/3/01 2:46 AM, permed@nor.com.au at permed@nor.com.au wrote:

> Many straws like wheat and triticale have hard cellulose structure which
> takes more nitrogen (e.g. from the soil, hence the plants they're
> mulching) to break down than finer straws and mulches.

Wheat is also an allelopath. Whether the toxins are stored in the stalks, or
are only secreted by the roots I don't know, but allelopathy may also be a
reason for lowered yields with a wheat mulch.

I've always been told that the beauty of mulch is that, unlike tilling
organic matter into the soil, mulch doesn't rob the soil of nitrogen because
the soil/mulch interface is of vastly reduced surface area compared to when
the "mulch" is tilled in. Thus, the theory goes, nitrogen uptake by
mulch-decomposing organisms is so small as to be negligible.

Also, I would think that a hard cellulose structure would decompose slower
than soft cellulose, which means *less* nitrogen uptake per unit of time.
And it seems to me that it takes the same number of nitrogen atoms to
combine with a given number of carbon atoms no matter what form the carbon
is in. It may be that wheat and triticale simply contain less nitrogen than,
say, oat or rice straw, or the particular decomposers involved require more
nitrogen for their own metabolisms. Just theorizing here.

Toby 
_____________________________________________
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