Research Article
Soil Fertility, Phosphorus Fractions, and Maize Yield as Affected by Poultry Manure and Single Superphosphate
Table 2
Sequential P fractionation procedures and targeted P forms.
| Location | Extractants | Equilibration | Washing | Targeted |
| NH4Cl-P |
IM NH4Cl | 30 mins | None | Saloid-bound P (loosely bound P) |
| NH4F-P | 0.5 M NH4F | 1 hour | None | Al-P |
| NaOH-P | 0.1 M NaOH saturated Nacl + 5 drops of conc. H2SO4 | 15 mins | Saturated Nacl | Fe-P |
| Sodium + citrate Sodium dithionite P | 0.3 M sodium citrate + 1 g solid Sodium dithionate + sat Nacl | Shake 15 mins, preheat 15 mins at 85°C after sodium citrate, additional 15 mins after dithionite addition | Saturated Nacl | Reductant-soluble P |
| NaOH-P |
0.1 M NaOH + few drops of conc. H2SO4 to remove colour | 15 mins | Saturated NaCl | Occluded P |
| H2SO4-P | 0.25 M H2SO4 + 25 mL Sat. Nacl | 1 hour | Saturated Nacl | Ca-P |
| Residual P | Conc. HNO3 + HCl + 30% H2O2 | Variable until complete | None | Organically stable organic and inorganic P |
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