Table 1 P fractionation in soils of Green Island chronosequence
Stage | Target P | Substrate | Extracted with | Procedure | Initial filtrate gives: | Digestion of filtrate with H2SO4, and H2O2 at 200 °C gives: |
|---|---|---|---|---|---|---|
Pretreatment: Air dry, grind in agate mortar, sieve to 2 mm, weigh 0.5Â g | ||||||
 Non-sequential | Total P | Pre-treated fine earth | H2SO4 and H2O2 | Digest sample in 97 % H2SO4, 30 %H2O2 & MgCl2 at 300oC | Pt |  |
 Sequential stage 1 | Labile | Pre-treated fine earth | KCl | Swirl sample in 30 ml 0.1 M KCl for 30 min at room temperature | KCl Pi |  |
 Sequential stage 2 | Moderately labile inorganic a organic | Residue from Stage 1 | NaHCO3 | Swirl sample in 30 ml 0.5 M NaHCO3 for 16 h at room temperature | NaHCO3 Pi | NaHCO3 Pt |
 Sequential stage 3 | Inorganic and organic on Fe and Al sesquioxides | Residue from Stage 2 | NaOH | Swirl sample in 30 ml 0.1 M NaOH for 16 h at room temperature | NaOH Pi | NaOH Pt |
 Sequential stage 4 | Calcareous and apatite | Residue from Stage 3 | HCl | Digest sample in 15 ml 1 M HCL for 16 h room temperature | HCl Pi |  |
 Sequential stage 5 | Residual P Strongly adsorbed or occluded | Residue from Stage 4 | H2SO4 and H2O2 | Digest residue in 97 % H2SO4, 30 %H2O2 & MgCl2 at 300oC | Residual P |  |