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Les, all,<br>
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On 12/7/2011 2:59 AM, Les Gornall wrote:
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<div class="WordSection1">Wayne,<br>
<br>
My first point of call for any fertiliser recommendations is
‘FERTILISER RECOMMENDATIONS’ otherwise known as RB209....<br>
<br>
From memory trials in Egypt in sandy soils crops were compared
from digested and undigested manures for decades (Halwagi et
al). The digestate crop yield was 15% better than the
undigested manure crop yield after 15 years. In other words the
soil was improving as a growing medium even in hot sandy soils.
<br>
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<br>
I guess nothing ever dies in the Internet. Digital eternity?<br>
<br>
I was interested in your mention of this, Les, and went spelunking,
thus encountering <a
href="http://www.repp.org/discussion/digestion/200002/msg00130.html">the
fragment below</a>, also posted by you to this list, but a decade
ago. Do forgive me therefore for quoting it-- your ideas may well
have changed, etc.-- but I thought it was a useful addition to this
discussion:<br>
<br>
<br>
<blockquote>
<blockquote>There are very few long term experiments relating
plant growth to the plant nutrients and micronutrients in
digested vs undigested organic wastes. - Have you ever tried to
get a grant for a 20 year research project?<br>
<br>
However, you should read :<br>
<br>
MOAWAD H., ZOHDY L.I., BADR EL-DIN S.M.S, KHALAFALLAH M.A.,
ABDEL-MAKSOUD H.K., 1984, "Assessment of anaerobically digested
slurry as a fertiliser and soil conditioner." in [El-] Halwagi
ed. Proc.Int. Conf. State of the art on Biogas Technology
Transfer and Diffusion, Cairo Nov. 17-24, Elsevier App.Sci.
499-519. <br>
</blockquote>
</blockquote>
<br>
The above appears to be the reference which memory prompted you to
cite, although perhaps it should be referenced as Moawad et al. You
go on:<br>
<blockquote>
<blockquote><br>
Also Zohdy L.I. et al 1984, "Repeated application of
anaerobically digested slurry and its effect on the yield and
NPK uptake of wheat, turnips and onion plants." (also in Halwagi
ed. above.)<br>
<br>
These workers found that whilst the annual difference in crop
mass was greater for AD than unD manures, the difference was not
significant statistically-- But the positive difference
accumulated year on year for many years and so after 15 years
you would expect almost 15% more crop mass. <br>
<br>
It seems to me that soils typically take 10,000 years to make
and 100 years to destroy. The aim of using AD is that the
decomposition of organic matter that would take place slowly in
the soil is done quickly in the digester. The AD effluent is
then used to rebuild the soil structure faster and more
efficiently than it is being destroyed by the agricultural
activity which itself depletes soil organics 100 times faster
than nature can repair the losses incurred by agriculture. <br>
<br>
If we put undigested sludge on the soil the soil first has to
grow the bacteria for decomposition and typical growth rates of
bacteria in soil (in Northern Ireland) are one doubling per year
as determined by soil respiration experiments (see the work of
Prof. A. McFadden in the 1970's). There are also other losses
from 'slurry spreading', nitrogen is lost, (bound up as
microbial protein in AD effluent), clovers and nitrogen fixing
plants are severely inhibited and earthworm populations fail,
reducing recycling.<br>
<br>
It is a big subject and one that is severely underfunded
academically.<br>
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<br>
<br>
<br>
<br>
d.<br>
<div class="moz-signature">-- <br>
<div style="font:Georgia" ;=""><span style="font-size:110%;">David
William House<br>
</span>
<div style="padding-left:3em;font-size:80%;">"The Complete
Biogas Handbook" <code><a href="www.completebiogas.com">www.completebiogas.com</a></code><br>
<em>Vahid Biogas</em>, an alternative energy consultancy <code><a
href="www.vahidbiogas.com">www.vahidbiogas.com</a><br>
<br>
</code></div>
<code>
<div style="padding-left:2em;">"Make no search for water.
But find thirst,<br>
And water from the very ground will burst."
<div style="padding-left:2em;font-size:80%;">(Rumi, a
Persian mystic poet, quoted in <em>Delight of Hearts</em>,
p. 77) <br>
<br>
<a class="moz-txt-link-freetext" href="http://bahai.us/">http://bahai.us/</a></div>
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