> Why should their goal be "not to have to import N onto their
> farm?" If they have a reasonably productive system that
> results in ample N and P exported off their farm as part of
> food or feed, then they must either import N onto the
> farm--or include an N-fixing crop in their rotations--or
> suffer the problem of N and P deficiency in their soils.
That's a good point. Exportation of nutrients off the farm seems to be a
> Why does sustainability have to be defined in terms of the
> individual farm? Why can't it be defined in terms of
> the watershed or other geographic unit
IMO, a failure to appreciate spatial and temporal scale is one factor that
has resulted in some unproductive effort in the environmentalist community.
The watershed would seem to a more natural unit for nutrient management than
> ...provided that inputs and outputs equilibrate?
Ideally the nitrogen and phosphorus consumed by humans and animals would be
returned to the farm. In current reality, most of it ends up in surface
water because the cost of transporting it to the farm is too high. If the
externalities associated with casual disposal of these wastes could be
captured and priced, transporting sludge and slurry to the farm (not just
nearby farms) would become economically feasible. I think public policy will
gradually come around to accomplish this.
> From an economic perspective, it may make perfect sense to
> be somewhere in the middle of the continuum between total
> specialization and total independence of the need
> for imported inputs--and still be sustainable.
Again, this is an issue of scaling. It may be okay for a farmer in Iowa to
grow mainly soybeans and corn, because that works well here, while someone
in Oregon produces grass seed, because they can do a better job of it there.
I think part of what is driving the farm unitization and independence sought
by some, is a romantic vision of farming that may not have ever really
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