The Use of Tracers to Investigate Phosphate Cycling in Soil–Plant Systems

The use of tracers is relevant to study the transformations of phosphorus (P) in the soil–plant system because (a) only a small fraction of the total soil P is rapidly circulating in this system, (b) P participates in many reactions in the soil, some occurring within a few seconds, others over years, and (c) P is distributed in many pools in the soil. This review presents the use of P radioisotopes (a) to probe pools and to study P transformations in soils, (b) to trace the fate of fertilizers in soil–plant systems, and (c) to assess the foraging strategies of arbuscular mycorrhizal fungi for P. Finally, we discuss the potential of analyzing the oxygen isotopes bound to P to study soil P dynamics and the research needed to achieve this aim.