Rhythmic radial oxygen loss enhances soil phosphorus bioavailability
Cai Li, Hu Sheng, Mengxi Tan, Hengyi Dai, Xiaolong Wang, Huacheng Xu, Shiming Ding, Guoqiang Zhao
Abstract
Phosphorus (P) availability is vital for global primary productivity, yet it is often immobilized in soils by redox-inert crystalline iron (oxy)hydroxides. Here we show that diel radial oxygen loss (ROL) from plant roots induces redox fluctuations in the rhizosphere, activating these iron minerals and enhancing P mobilization. Nighttime reduction and daytime oxidation drive the formation of reactive metastable iron phases (RMPs) on root surfaces, forming a redox-active iron plaque. These RMPs undergo rapid dissolution–reformation cycles, facilitating P transfer from soil to porewater for plant uptake. Using multiple aquatic plants from agriculturally developed regions, we demonstrate that ROL broadly enhances soil P availability. In rice paddies, ROL-activated P release accounts for 8.7% of global P fertilizer input, contributing an estimated economic value of USD 0.52 billion annually. Our findings uncover a previously overlooked redox mechanism by which plants enhance P acquisition, with broad implications for nutrient cycling and agricultural sustainability. Rhizosphere oxygen loss from plant roots transforms redox-inert iron into reactive metastable phases, enhancing phosphorus mobility and nutrient availability in soils, boosting plant growth, sustainability, and delivering significant agricultural and economic benefits.