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10
Unravelling the myths
Phosphate in Fibrophos
3
The history of Phosphate
Dissolved bones formed the first
‘manufactured’ phosphate fertilisers
and this was shortly followed by
slag from blast furnaces.
Phosphate is vital for root
development and the seed ripening
process. It is taken up by the plant as
either dihydrogen phosphate (H
2
P0
4
)
or hydrogen phosphate (HP0
4
2-
).
Phosphorus as a fertiliser is always
expressed as phosphate P
2
0
5
in
the UK.
Phosphate in the soil
Phosphate exists in the soil as two
basic forms:
Organic Phosphate
30-50% of total phosphate in UK soils
is in this form as a series of complex
substances. It can be released by
micro-organisms to form hydrogen
phosphates, the timing of which
does not always coincide with when
the plant needs it.
Inorganic Phosphate
The balance of phosphates are held
as either calcium phosphates with
varying degrees of availability, often
on calcareous soils with high pH or
as iron or aluminium phosphates –
particularly on acid clay soils.