Nearly all methods of determining P in soil involve
extraction of P into a liquid phase. Deionized w
ater (DI) is
a commonly used extractant for P analysis,
5
and ammonium oxalate (AmOx) is a multipurpose extr
actant that can be
used for cation analysis and P determination.
6,7,8
Oxalate binds to cations, pulling some of them fr
om soil particles.
An ammonium oxalate solution will extract more phos
phate from soil than will DI, because the oxalate c
an replace
the phosphate at cationic sites on soil particles.
AmOx extractions are of agronomic significance, be
cause they more
closely approximate the P that is available to plan
ts. DI extractable P is of particular environmenta
l significance,
because it is an indicator of P run-off susceptibil
ity.
Nearly all methods of determining P in soil involve extraction of P into a liquid phase. Deionized water (DI) is a commonly used extractant for P analysis,5 and ammonium oxalate (AmOx) is a multipurpose extractant that can be used for cation analysis and P determination.6,7,8 Oxalate binds to cations, pulling some of them from soil particles. An ammonium oxalate solution will extract more phosphate from soil than will DI, because the oxalate can replace the phosphate at cationic sites on soil particles. AmOx extractions are of agronomic significance, because they more closely approximate the P that is available to plants. DI extractable P is of particular environmental significance, because it is an indicator of P run-off susceptibility.
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