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 (delta O-18-P). The scientific community interested in using this isotopic tracer is slowly but steadily expanding because delta O-18-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.