Back in 1998, Joel Gruver made the following post to
SANET: http://www.sare.org/sanet-mg/archives/html-home/28-html/0043.html Hello to all... My
focus was on soil structural effects... in a nutshell, the process The
issue of differences in carbon sequestration was not discussed in many Our
literature sits almost finished somewhere in Dr. Weils office... I Joel
Gruver Other
folks joined in, including Steve Diver and Cary Oshins; this was the post that
seemed to get things started: http://www.sare.org/sanet-mg/archives/html-home/28-html/0037.html > Dan Hemenway wrote: On
the topic on sheet mulch composting in place versus composting The
benefits and uses of compost as a stable humus product I
came across the following Sanet post by Ann Clark back in 1995, Steve
Diver >From: "E. Ann Clark, Associate
Professor" Responding
to Dick R. on the issue of composting. Just curious about
Good
points on "waste" management at landfills! Ann Steve
Diver’s follow up post added the following points: http://www.sare.org/sanet-mg/archives/html-home/28-html/0045.html “There's a little-known but valuable publication
from Wallace One
of the articles titled "Compost and Composting: Facts Selected
excerpts: "Most
people think that making compost is to create fertilizer. 1.
to decrease the volume of waste, especially for going into "For
improvement of physical properties of soil, actual decomposition Recently
I have been having a discussion with Dave Schellinger over on the USCC list
(compost list) concerning this very matter. Mr Schellinger put forward the view
that raw organic matter actually decreases aggregate formation in the soil, and
cited some literature claiming to support his point: “Humus binds clay particles, but raw organic matter disperses and
reduces aggregates. Bohn, et al., 2001, points out that greater
aggregation produces less stable organic matter contents in soils due to
increased aeration and microbiological degradation. Even aggregates
become less stable with added organic matter. This coincides with my
statement that raw organic matter additions reduces ped formation. Approximately
50-80% of fresh organic matter is lost from most temperate soils in the year of
application, just like during the composting process. And, the smaller
the particle size, the faster the degradation occurs. If more organic
matter is added to the soil, it degrades faster. The book points to an
experiment in Mr.
Schellinger also put forward the proposition that the addition of raw organic
materials to soils increased production of various greenhouse gases, aside from
CO2, compared to composting prior to soil application. In large part I think he
based this on the risk of flooding and excessive rain; his location in I put forward
the counter proposition, that raw organic residues could well improve the
greenhouse gas status of a soil, if they resulted in improved soil structure
and subsequent improved plant growth. The importance of seeing the full picture
of these scenarios is great, I believe. I would certainly appreciate input from
Joel Gruver and others concerning our current understanding of these matters. I
did cite in our exchange the work of Dr Fred Magdoff, who actually compared two
scenarios of manure management and found direct application of manure to yield
better aggregation than composting the manure first: http://www.mofga.org/mofgj00j.html
It should also
be noted that no tillage scenario I am aware of allows for a sustainable return
to uncultivated SOM levels without heroic applications of organic matter, and
this because tillage is itself a major destructive force against SOM. However,
by using rotations including several years of proper pasturing soil can be kept
at acceptable The question
of ‘to compost, or not to compost’ hits farmers squarely in the
face, especially those whose livestock are fed exclusively or nearly so from
the farm acreage itself. One factor we did not discuss is the issue of
transportation costs and the mechanical costs of composting, which obviously
also have greenhouse gas consequences. Labor time savings for the farmer are
also an issue. This is less of an issue where manure producers rely on
transported inputs and generate large quantities of manure which must
subsequently be retransported substantial distances; there the calculus should favor
composting on shipping cost grounds quite strongly. Of course, the farm’s
overall crop diversity and the need for mature, relatively weed free compost
for specific crops are also factors which the decision maker needs to consider. I actually experience an opposite situation. I have
access to large quantities of shredded compressed dry fall leaves. In my view
it clearly seems favourable to transport these as is to my growing site prior
to application, rather than composting them first which would mean the addition
of a substantial amount of water, as well as requiring space which at present
is unavailable. This might be analogous to the handling of hay, which when dry
and bailed can be transported more cost effectively than if it were composted
and moist. There remains the issue of whether to compost prior to soil
application, of course. With hay the issue of weed seeds looms large, for any
future open soil growing; even with leaves there is some potential for weed
seed presence. I consider that the use of these leaves both as mulch
and as incorporated organic matter will predominate in the mixed vegetable,
small fruit and tree orchard context which I participate in. Doubtless some
will also be thermally and worm composted as well, to produce materials for
compost teas and watery extracts as well as direct applications. I believe that
my sandy soil will benefit from direct decomposition of the leaves and
subsequent fungal growth in the soil itself more than if all the leaves were composted
before application. Because this soil is very well drained I anticipate no
serious anaerobicity problems leading to methane or NOx production as a result.
In more poorly drained soils that experience spring and/or fall flooding, it
could very well be wise to compost and apply shortly before planting, or as
crop choices permit, to apply after danger of flooding is past but with
sufficient time to decompose prior to planting. I would appreciate any specific or general comments
on these subjects. I can make the full text of the exchanges between myself and
Mr Schellinger available to anyone interested. Frank Teuton   ***************************************************** To unsubscribe from SANET-MG: 1- Visit http://lists.sare.org/archives/sanet-mg.html
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