Oxygen Isotopes for Unraveling Phosphorus Transformations in the Soil-Plant System: A Review

Phosphorus is a major nutrient for all living organisms. In the terrestrial environment, P is considered a double-edged sword. In some areas, agricultural production is strongly limited by the low soil P availability, while in others, P inputs in excess of plant needs have resulted in pollution of water bodies. A better understanding of soil–plant P cycling is needed to provide agricultural and environmental managers with better concepts for P use. Together with the routine analysis of soil available P, the determination of P chemical forms, and the use of P radioisotopes, researchers have recently started using the ratio of stable oxygen isotopes in phosphate (δ18O-P). The scientific community interested in using this isotopic tracer is slowly but steadily expanding because δ18O-P has proven to provide important information on biological processes influencing the P cycle and it could be used to trace the origin and fate of P in soil–plant systems. This review examines the published results and compiles the available data relevant for soil–plant systems, pinpoints gaps in analytical techniques and knowledge, and suggests key questions and topics to be investigated.