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Re: Is mulch sustainable?

On Thu, 05 Jun 1997 01:26:42 GMT, I wrote:

>If, for example, I grow hay for use as mulch, I
>...
>would need an additional 8 hectares of hayfield for
>each hectare of vineyard.
>
>If, on the other hand, I chip up my woodlot, I should
>... need 70 hectares of woodlot for each hectare of vineyard. 

I too was shocked when I came up with these numbers
but I am more and more convinced that they are right
to order of magnitude. I have since been doing some
more calculations.

My current method of weed control is hoeing and
tilling, combined with as much mulch as I can get
(which is a tiny amount compared to the above figures)
and manure. I have lost about 1% organic matter in
10 years. Taking this as being from the top 15 cm
with a mean density 1.6 tonnes/hectare, this comes to
a loss of 24 tonnes/hectare. I have added an estimated
25 tonnes/hectare of organic matter so the total loss
comes out at 49 tonnes/hectare or say 5 tonnes/(hectare
year) in round figures.

Does anybody have any figures for comparable cases or for
straight tilling?

Taking the mulch figures from my original post and
assuming the mulch to be 50% organic matter as dry
weight gives a loss rate of something over 40
tonnes/(hectare year) or 8 times as much. This
seems high but presumably reflects the dramatically
increased soil activity so often referred to on a.s.a.
The mulch is, after all, fully exposed to the air.

Again; does anybody have reliable measurements for
comparable cases?

Andrew Bennett; Avondale Vineyard
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