> We think of N as 'limiting factor' on the process-thus
> recommendations such as were made to add synthetic N
> salts to the sawdust manure mixture. But this is a
> cop out. It is like having a broken wind mill and
> 'fixing it' by hooking the pump up to an electric
> motor-it solves the immediate problem of pumping water
> but it doesn't achieve the real goal which is to pump
> water cheaply from wind energy. Spaying N fertilizer on
> your compost supplies the temporarily scarce N to the
> plants, but it doesn't reach the real goal which is to
> tune the soil microbiology so that sufficient N is built
> up naturally.
But for most farmers, the "real goal" is productivity of the land in terms
of marketable products. All the stuff you are talking about is more like
the bearings of the windmill, catalysts to productivity. The core
biological process is the capture of solar energy via photosynthesis in the
form of products that people want. If higher productivity can be achieved
by exogenous nitrogen without excessive environmental degredation, then
there is no biological reason farmers should not use fertilizer regardless
the specific effect on Azotobacter.
> In fact, the synthetic N actually disrupts that microbiology
> and is, therefore counterproductive, not to mention expensive
> and environmentally unsound.
By "that microbiology" do you mean specifically non-rhizobial nitrogen
fixation, or the general microbiological diversity and health of the soil?
Exogenous N (mineral or organic) inhibits nitrogen fixation, because
N-fixation is costly to the fixer in terms of energy. But there is no
evidence that modest addition of exogenous N decreases organic matter, or
injures soil flora and fauna. In fact, by increasing productivity, organic
matter additions to the soil are increased by N fertilization, whether
synthetic or not.
> One key organism seems to be Azotobacter-this aerobic,
> free-living bacteria does almost everything we want.
Sure, organisms like Azotobacter and Azospirillium are desirable, but they
don't add enough N for economically sustainable crop production, and in the
big picture are not the central issue.
I respect the "organic mythos" as an esthetic value, and consider "organic"
gardening to be an interesting challenge. But I can't see any biological
reason why modest additions of fertilizer are detrimental to long-term soil
health. It is drainage and tillage that burns up the soil, not fertilizer.
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