Evaluation of phosphorus mobility in soil using different extraction methods

Abstract

Soil samples (from Czech and German long-term field experiments) were used to estimate different soil phosphorus (P) fractions. More than 200 topsoil (0-30 cm) samples from different fertilizing treatments were taken. These were analyzed for P in soil solution (PCaCl2) [0.01M CaCl2 extract], exchangeable sorbed P (Pex) [anion exchange (AE) membranes] and bioavailable P [Doppel-Lactat and Mehlich 3 (PDL and PM3)]. Other fractions analyzed were total inorganic (Pin), total (PM-tot) and organic (Porg) P [fractionation after Marks], P sorbed on Fe and Al (PFeAl) [fractionation after Schwertmann] and residual P (Par) [aqua regia extract]. Comparison of medians appeared to be better for evaluating extraction abilities. Phosphorus fractions were in the following order: (Par = 100%); PCaCl2 (0.2%) < Pex (9%) < PDL (10%) < PM3 (16%) < Pin (24%) < Porg (37%) < PFeAl (55%) < PM-tot (59%). Low amounts of Pin, Porg and PM-tot did not verify the applicability of the Marks' fractionation for the set of studied soils. Close correlations at P ≤ 0.001 were found for all methods for estimating the fractions of bioavailable phosphates (PCaCl2, Pex, PDL and PM3). Statistically significant relations were observed between Pin with Par, PM-tot and PFeAl.