I am enjoying this strand, and it has made me want to brush up on
chemical interactions in the soil solution!
Here is another scenerio studied by one of my cohort in school:
Phosphorus fertilization is promoted by the horticulture industry
particular for flowering plants. Our damaged soils are typically low in
calcium with low CEC. Excess soluble phosphorus immobilizes by bonding
with available iron, resulting in iron deficiencies in some succeptible
species.
Another angle:
Rock phospate (and thus all those phosphorus products) is a limited
resource only found in a few places on earth (florida, morocco, ??).
Control of these resources is critical to industrial agriculture, and
perhaps all eurasian inspired agriculture is some soil types.
Extraction of this non-renewable resource requires political control,
mining and energy intensive shipping. Why would those who support local
control, decentralization and reduction on energy dependance promote
this economy? I am wary of engaging in the scrabble for the last easily
extractable phosphorus on earth.
(and a side note.. a local organic guru Steve Solomon made a precise
critique of Fukuoka's continuous grain harvest system by noticing that
he is farming on phosphorus rich soils.)
Thanks Lawrence for the tip on local quarries... duh!... I will check
out my local rock crusher, their source of stone, and if they spray
floculants (which i know little about) for dust control.
I feel compelled to make a plug for working carefully with your existing
mineral base. Although we can manipulate the pools of various elements
in the soil, I'd be willing to bet that the continuous availability of
those elements is dependant on biological activity that increases the
cycling of elements, and thier incorporation into soil food webs. And
that stable humus so strongly mediates cation exchange and phosphorus
cycling that increasing the insoluble pool is less critical than good
cycling and biological development in many soils. At some point rock
powder ammendment can be a side track if other factors are limiting
plant health or if the system is producing 'well enough' such that the
marginal return on rock powders isn't ecologically justifiable. Rock
powders obtained from far flung surface mining conglomerates, are energy
intensive commodities -- and there are local sources of waste phosphorus.
I know all you folks are thinking about these things... but I know that
our culture has a proclivity toward reducing complex things into
consumer solutions... and so I take the soap box (no phosphate pun
intended) only out of compulsion -- no patronization intended. The
'health and sustainability' market is just beginning to mature, and the
snake-oil salesmen have always loved gardeners.
Anyone have any good resources on 'dynamic accumulators' of phosphorus
or other elements?