Rapid microbial phosphorus immobilization dominates gross phosphorus fluxes in a grassland soil with low inorganic phosphorus availability

► Low P availability in a grassland soil caused rapid microbial P immobilization. ► A microbial inhibitor was required in the isotopic dilution method. ► Gross P mineralization was at least equal to isotopically exchangeable P. ► This shows the importance of microbial processes in soil P dynamics.