KEYNOTE Dynamic phosphorus cycling patterns in China

Phosphorus (P), an essential nutrient for living systems, has altered its biogeochemical cycle globally and is running out with no substitutes. Considering its temporal dynamics are still unclear, we quantify the P pathways... [ view full abstract ]

Phosphorus (P), an essential nutrient for living systems, has altered its biogeochemical cycle globally and is running out with no substitutes. Considering its temporal dynamics are still unclear, we quantify the P pathways across China over the last four centuries with a process-balanced model. We find that P cycles in China have been artificially intensified during this period to sustain the increasing populations, especially their demands for animal protein-based diets, with continuous accumulations in inland waters (from 0.44 to 1.57 Tg-P·yr-1) and arable and non-arable lands (from -0.75 to 7.95 Tg-P·yr-1). Although per capita food-P demand has not changed substantially, the contribution of crop products has reduced from over 98% before the 1950s to 76% in 2012. In the last decade, China’s international trade of P involves net exports of P chemicals and net imports of downstream crops, specifically the soybeans from the United States, Brazil and Argentina. Chinese domestic P reserve depletion can be postponed for over 20 years through the improvement of agronomic efficiency without decreasing the current crop yields, and other opportunities exist in the recycling of abundant P legacy in soils and ocean sediments. Our results advance the knowledge of closing P cycle to achieve the co-benefits of P resource conservation and eutrophication mitigation.