Phosphorus fractions and oxygen isotope composition of inorganic phosphate in typical agricultural soils

Phosphorus (P), despite being an essential nutrient element for plants growth in agricultural ecosystem, the low utilization rate of soil P and the environmental problems caused by soil P losses are serious. Therefore, scoping knowledge of the possible sources and utilization extent of soil P by microorganisms is very helpful for better understanding of promoting P utilization for sustainable agriculture. Oxygen isotope of phosphate technology is an effective tool to trace the sources of P. In this study, P contents and oxygen isotope composition of inorganic phosphate (δ¹⁸O_P) of different pools (H₂O-P, NaHCO₃-P, NaOH-P, and HCl-P) in typical agricultural soil from Northeast China and Central China were analyzed and quantified. The results showed that fertilizer and land use were important factors influencing the contents of H₂O-P_t and NaHCO₃-P_t and the soil TP contents from different types of soils were greatly affected by soil weathering degree. The δ¹⁸O_P of different P pools indicated that the difference in utilization extent of different P fractions by microorganisms and the δ¹⁸O_P values of different P fractions could be due to accumulation of multiple factors. The results will provide effective information for further study on sources and effective utilization of different P fractions in soil.