Alternative approach to the standard, measurements and testing programme used to establish phosphorus fractionation in soils

Highlights: • An alternative method for the determination of phosphorus (P) forms is proposed. • Total, inorganic and organic P are easily assessed by calculation. • P forms depended on non-apatite and apatite P measured by GFAAS and UV-visible. - Abstract: The fractionation of phosphorus in 9 soils was established according to the standards, measurements and testing (SMT) programme. Five fractions were so defined and phosphorus was analysed by spectrophotometry. In parallel, the phosphorus extracted in each fraction was determined using graphite furnace atomic absorption spectrometry (GFAAS) after validation of this technique using certified reference materials. Phosphorus in soils was named total phosphorus, inorganic and organic phosphorus, apatite and non-apatite inorganic phosphorus, depending on extractants. The use of both analytical techniques revealed differences between the concentration of phosphorus in soluble extracts and highlighted the fact that spectrophotometry was a selective analytical technique. In view of the resource- and time-consuming of the SMT procedure and the results obtained in the present study, an alternative method was proposed to estimate the fractionation of phosphorus in soil in order to precise the potential effects of phosphorus on plant nutrition when plant biomass is produced as part of metal-contaminated soil management.