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On Fri, Aug 17, 2007 at 09:04:27AM -0700, Alex Harford wrote:
> On 8/16/07, Peter Todd <pete@petertodd.ca> wrote:
> >
> > A similar issue is how often when you trace where nutrients are coming
> > from you find that organic farming is indirectly dependent on chemical
> > fertilizers. Farming will always remove nutrients from the soil, for the
> > obvious reason that plants are made up of more than carbon, oxygen and
> > nitrogen. Organic farming is often heavilly dependent on adding
> > manure to the soil to make up for that loss. But, where do the nutrients
> > in the manure come from? Usually from chemical fertilizers, applied
> > to a nearby non-organic farm...
> >
> 
> Like James, I use a mulch method in my vegetable garden and I agree
> that it difficult to scale to a large scale farming operation.
> 
> But I have to disagree about using manures to make up for lost trace
> elements in the soil.  Many organic farmers are concerned about using
> manures because of the antibiotics and other chemicals that are used
> in the raising of cattle.  These people will use ocean based
> supplements, whether it's seaweed, algae, fish fertilizer, ground
> shellfish shells, etc.

Of course, and good for them for sticking to their principles. But lots
of organic farming these days is simply a business choice by producers
who don't want to be making commodities. I'm sure all they care about is
can they get an organic label stamped on their product.

> It's a wonder that our farming society has survived for 2000+ years
> without petroleum based fertilizers at all! ;-)

The point is, often they didn't. Historically it hasn't been uncommon
for yields in an area to slowly drop until farming was impractical.
That's why places like the Nile valley were renowed, yearly free
fertilizer. It's also apparent when looking at the history of a lot of
places that areas where farming has always been successfull had a lot of
top soil, IE, a very large buffer to slowly work through. The
aboriginals of Australia, for instance, never managed to farm, and where
they live has notoriously thin topsoil that gets depleated very quickly
without a lot of extra fertilizers. Slash and burn farming has gone on
long before modern history in rainforests, again, a rainforest has
practically no topsoil and a cleared plot can only be farmed for a few
years.

Aparently larger plants, especially trees, are a big exception to this.
Forests don't need fertilizers, even after multiple cycles of logging,
because the trees in them are quite capable of mechanically
breaking up rock, and chemically releasing the nutrients in the
rock. A very round about form of mining. It also helps that wood has
relatively low amounts of anything but carbon in it in the first place,
so trees have similarly low nutrient requierments.

- -- 
http://petertodd.org
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