"David Hare-Scott" wrote:
Dan L wrote:
Billy wrote:
In article ,
Bert Hyman wrote:

In

Billy wrote:

I'm not arguing for local food because it tastes better or because
it's better for you. I'm arguing that we have no choice. In a
world
more prone to drought and flood, we need the resilience that comes
with three dozen different crops in one field, not a vast ocean of
corn or soybeans. In a world where warmth spreads pests more
efficiently, we need the resilience of many local varieties and
breeds. And in a world with less oil, we need the kind of small,
mixed farms that can provide their own fertilizer and build their
own
soil.

Who's going to be the person to tell 2/3 of the earth's population
that
they're going to have to starve?

That would be the fossil-fuel, industrial, corporate farmers, waving
their price lists about for people to inspect.

If you have followed the thread, Bert, you would have seen numbers
that
indicate that we are getting diminishing returns from industrial
farming, and industrial farming is based on increasingly expensive
fossil fuels (2200 lbs of coal for 5.5 lbs of nitrogen fertilizer?).

Joel Salatin on his farm in the Shenandoah Valley of Virginia,
yearly
transforms his pastures into "40,000 pounds of beef, 30,000 pounds
of
pork, 10,000 broilers, 1,200 turkeys, 1,000 rabbits, and 35,000
dozen
eggs. This is an astounding cornucopia of food to draw from a
hundred
acres of pasture, yet what is perhaps still more astonishing is the
fact
that this pasture will be in no way diminished by the process‹in
fact,

it will be the better for it, lusher, more fertile, even springier
underfoot (this thanks to the increased earthworm traffic)."


-----
He grows an inch of topsoil/year.

I believe in the theory "The world is a zero sum gain".

Perhaps you mean "zero sum game". This is where there is only a fixed
amount in the pot, the total gained by the winners must be made up by
the total lost by the losers. I don't think it is true to say that of
the world in general. It is true of fixed resources eg oil but much
of the living world is not a fixed resource like that. For example
while it is technically true that there is only a fixed amount of some
plant nutrients (for example nitrogen) in the earth's biosphere humans
only need a tiny fraction of it and if we recycle it well then it
effectively becomes limitless.


If food and
population grows it is at the expense of nature. Predator vs Prey and
so on.
So Joel Salatin grows thousands of pounds of food and improves his
soil. If this true where does he get thousands of pounds of material
to go back into his soil?

From air and rain. The great bulk of biomass comes from carbon
dioxide in the air, nitrogen in the air and rainwater.

Does the amount of rain that falls on his land have as much substance
that leaves his farm in food production?

Not exactly, see above and this:

http://en.wikipedia.org/wiki/Nitrogen_cycle

and this

http://en.wikipedia.org/wiki/Carbon_cycle

I bet he also buys "lime"
and other soil improving substances as well. If he does buy lime and
other soil improvements, is he really self sustaining? Or are using
the term self sustaining in terms of economics?


He probably does by some minor inputs such as lime. The aim in
sustainable agriculture at this stage is not to produce a perfect
closed system where nothing is lost so nothing needs to be input
except sunlight - although some people are actually experimenting
with that. The aim is to get away from reliance on fixed resources,
especially energy sources like fossil fuels which are going to run out
fairly soon. This is because if we don't our present system of
agriculture will fall in a heap.

In the future we may well have to worry about running out of lime or
phosphate rock but those limits are not urgent now. It is going to be
hard enough dealing with climate change, fossil fuel running out,
water being used inefficiently and over population adding more
pressure every day, let's get those out of the way first.

David

Thanks for the clarification, The term "closed system" is the key word
that I was associating with "sustainable".

--
Enjoy Life... Dan L