Analysis of phosphorus forms on different soil types using heterogeneous isotope exchange reaction

Abstract

Pot experiments and soil incubation were carried out to follow the processes of added phosphorus (P) fertilizer using radioisotope tracer technique, heterogeneous isotope exchange. Four types of soils were investigated (Dystric Arenosol (Humic), Calcic Vertisol (Gleyic), Rendzic Phaeozem (Hyperhumic), Calcic Gleysol(Arenic, Humic)). The changes of phosphate fractions (water-soluble (Pw), isotopically exchangeable (PIE), ammonium lactate soluble phosphorus (PAL), and tightly sorbed phosphorus (Ptightly)) in soil were determined as a function of P supply, incubation time and the plant culture. The soil samples were incubated at different times (1, 3, 13 weeks) and phosphate quantities. 0, 40, 80, 160, 320 mg P/kg soil doses of P fertilizer were added to the soils. After incubation, perennial ryegrass (Lolium perenne L.) was sown. A significant correlation was found between the sum of Pw and PIE and Puptake of plant proving that these values can be good indicators of plant available phosphorus. During plant culture, the Pw and PIE values always decrease showing that plant directly utilizes these phosphate forms. The transformation of added phosphate to tightly sorbed phosphate is the highest for soils with great humus content.