A synthesis of phosphorus stocks and fluxes in natural and agricultural environments

Estimates of phosphorus (P) fluxes at the global scale were already available in the early 2010s and led to the establishment of planetary boundaries for P.  In the meantime, estimates of P stocks and fluxes have been revised and updated for natural biomes, agriculture, fishery, and global biogeochemical models. However, improvements toward attaining P-related sustainable development goals requires policies informed by the situation at the corresponding scales, ranging from plot to national to global scale. Here, we bridge this gap by synthesizing the relative sizes of P stocks and fluxes in natural and agricultural terrestrial environments from existing literature, focusing on the plot scale. Though the P cycle is context specific, our analysis of roughly 790 empirical flux measurements from 27 studies supports drawing several general conclusions about relative magnitudes of P stocks and fluxes. For example, in both natural and agricultural systems, empirical data on P stocks tend to follow the pattern soil >> microbial biomass > plant biomass. Similarly, we summarize empirical measurements of P fluxes and show that in natural ecosystems, fluxes between P pools within soil >> fluxes between soils-plants > system inputs (weathering, atmospheric deposition) and losses (erosion, leaching). We also discuss specific contexts where these general patterns do not hold, and what that means for management. Finally, we will discuss how a better understanding of P stocks and fluxes is relevant for science-informed management of P resources, for example through improved representation of P in vegetation or crop models.