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Updated: Jan 11, 2026

Measuring Phosphorus Release in Laboratory Microcosms for Water Quality Assessment
Published on: July 22, 2019
Redox-mediated Fe-P coupling modulates phosphorus releasing in paddy soils: Hydrological controls under water-saving
Yun Li1, Minghong Chen1, Xuanye Liu1
1State Key Laboratory of Efficient Utilization of Agricultural Water Resources, China Agricultural University, Beijing 100083, China; Center for Agricultural Water Research in China, China Agricultural University, Beijing 100083, China.
Abstract:
Agricultural non-point phosphorus (P) pollution from paddy fields threatens aquatic ecosystems. This study quantified the effects of irrigation practices on vertical P distribution and transport in paddy soils using high-resolution in situ monitoring. Rice was cultivated in the Heping Irrigation District under three regimes: controlled irrigation (CI), alternate wetting and drying (AWD), and conventional flooding (CF). Rhizosphere-scale dissolved oxygen (DO), iron (Fe), and P distributions were characterized using Unisense microelectrodes, DGT, and HR-Peeper devices. Results demonstrated that aerobic layer thickness and DO at the soil-water interface (SWI) followed CI > AWD > CF, whereas porewater Fe2+ and PO₄3- exhibited the reverse trend (CI < AWD < CF). CI reduced PO₄3- flux to overlying water by 8.3-58.5 % versus CF during drainage periods, due to its enhanced P adsorption capacity (Kd + 22.8 %) and sustained resupply ability (R + 0.9 % and Tc + 71.4 %). This demonstrates that irrigation-driven redox control regulates Fe-P coupling to minimize P mobility. Water-saving irrigation adoption must prioritize redox optimization to mitigate P release while conserving water.
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