Determination of available phosphorus in soils from northern Greece by the electro-ultrafiltration (EUF) and other methods of soil analysis

The suitability of electro-ultrafiltration (EUF) and other methods of soil analysis, commonly practised worldwide, for the assessment of available phosphorus (P) in 21 sails taken from various locations of northern Greece, as defined by P uptake and dry matter yield of ryegrass grown in pots, was studied. Significant correlations were found to exist between the quantities of P uptake by ryegrass and those of P extracted by the various methods. Phosphorus uptake by ryegrass correlated best with the P-resin contents (r = 0.91***), while the poorest correlation was observed with the organic P fraction (r = 0.53*). The correlation between EUF-P at 20 degrees C and P uptake by ryegrass was highly significant (r = 0.84***) and became even higher when the values of the quotient EUF-P 80 degrees C/EUF-P 20 degrees C, i.e. the P reserves, were taken into account. Of all the methods tested, the Olsen-P method proved least sensitive to changes in pH, texture, cation exchange capacity (CEC), and percent base saturation.