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HUMUS (fwd)
I operate under the assumption that native soil levels were much higher
than the current averages, so that some of the atmospheric CO2 which
stimulates the global warming debate was once in the form of soil
carbon. It seems rather ludicrous to debate whether or not we
"should" decrease atmospheric CO2 in order to increase soil humus
levels. Many of the forgotten pages of debate over atmospheric warming
deal with "carbon banks" such as the biosphere and humusphere as "sinks"
which are capable of reducing global CO2.
My concerns were not directly related to the benefit or detriment of
placing more atmospheric carbon into the "humusphere/soil". In fact, I
think the majority would agree that to remove carbon from the atmosphere,
banking it in the soil, would only benefit all cylces involved. My main
concern is to assert that one could build soil organic carbon by 13% in
10 years without importing carbon from an off-farm source. I am totally
in agreement that those off-farm sources of carbon should be cycled back
through the soil. The merits of the Luebke soil management system was
partially based on their ability to increase organic matter. I felt that
more information was needed regarding the source of their carbon and scale
of operation. To increase the soil organic matter of 200 acres by
promoting soil life and crop rotation is much different than a heavily
managed garden.
The Thompsons from Iowa have made arrangments
HH> with the local village to use the carbon, in the form of organic
HH> waste, as a cost effective amendment to their soil. Would all
HH> farmers need to compete for these contracts, or could the carbon be
HH> produced on-farm.
If you are looking at the long term mass balance of available carbon
such as residuals from the public sector, I am afraid that the volume of
organic material landfilled, about one wet ton per capita, is inadequate
for the demand of our acreages of soil needing organic matter. It is
doubtful that even half of the landfilled organic waste can be recovered
into a usable form without carrying with it all manner of pollutants and
undesirable particulates. The composting process itself converts up to
1/3 of its volume into heat and CO2, so even 50 million tons of organic
matter to be recovered annually is a liberal estimate.
My numbers may be off, but it is my understanding that we have upwards
of 350 million acres of farmland, so this represents about 1/7th of a
ton per acre. Sustainable compost demand would be more in the 5 to 10
tons per acre annual range. To bring soil humus up to ambient, which I
claim is a sustainable level, would require upwards of 200 tons per
acre. This represents a "topsoil debt" as high as 7 trillion tons of
compost.
Focusing on recovering the wasted organic fraction which is
thoughtlessly landfilled seems a reasonable place to begin development
of a carbon management infrastructure in modern agriculture. This
material is capable of being subsidized in the form of transportation,
landfill and disposal fees whereas on-farm organics must pay their own
way. I look at diverting urban organic matter from landfills to farms
as an important first, and more than symbolic step toward increased
interdependence between agricultural producers and consumers.
But you are correct, Thomas, in pointing out that ultimately farms must
eventually be responsible for their own carbon debt and annual carbon
requirement. This may occur within various bio-regions where certain
farms might become biomass cultivators capable of supplying the carbon
requirements for farms within their region. But unless our mentality
concerning renewable carbon gets some infusions of entepreneurism, the
fossil carbon commodity infrastructure will continue to supply the
chemical dependency addiction with few compunctions.
I am intrigued by the discussion related to types of microbes and other
means of determining the organic fertility of a soil. I would add to
the discussion some questions concerning phosphorus limits which are
increasingly becoming an environmental driver (revenue source) related
to non point water pollution.
The synergistic interactions of a healthy soil ecosystem including
microbes, fungi, earthworms, and the various other organisms which
thrive in a healthy humusphere may have values related to soil tilth,
water holding capacity, pH buffering, nutrient availability, and cost of
tillage. Unknown or currently unquantified values such as growth
hormones, pheromes, anti-biotics, disease suppression, and pest
retardation may be unexpected but indicated assets resulting from humus
rich environments.
In summary, other values of humus such as water quality, energy, waste
disposal, and atmospheric warming might increasingly become economic
levers in which to wean agriculture from the dependency on fossil carbon
and help make the transition to renewable carbon based farming. To me,
the focus on renewable carbon should be at the heart of the sustainable
agriculture debate.
Mr Compost~~~
Jim~ McNelly
jim.mcnelly@granite.mn.org
* RM 1.3 02460 * What profit to gain the world and lose your soil?
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Email: jim.mcnelly@granite.mn.org (Jim Mcnelly)
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Thomas Hansmeyer
St. Paul MN
hansm001@maroon.tc.umn.edu