Ferric Oxide Nanoparticles Foliar Application Effectively Enhanced Iron Bioavailability and Rice Quality in Rice (Oryza sativa L.) Grains

Synergizing iron nutrition and rice quality is essential for the development of integrated high-quality rice. In this study, a two-year field experiment was conducted to investigate the influence of ferric oxide nanoparticles (Fe2O3 NPs) foliar spraying on rice yield, quality, and iron bioavailability, with spraying water as the control (CK). Our results demonstrate that Fe2O3 NPs foliar application increase grain yield by 1.22–3.97% for the improved filled grain rate and 1000-grain weight, essentially attributed to improved net photosynthetic rate and SPAD value after heading. In addition, Fe2O3 NPs application achieved a higher rate of brown rice, polished rice, and head rice, and decreased chalkiness grain rate and chalkiness degree. Rice taste value treated with Fe2O3 NPs application was notably increased by 2.75–9.43% compared to CK, respectively, which is also reflected in the superior breakdown value (5.85–15.18%) and inferior setback value (12.38–28.19%). Meanwhile, foliar spraying Fe2O3 NPs significantly increased the iron content (16.97–58.74% and 26.48–94.01%) and proportion (2.90–5.35% and 13.10–26.44%), while they decreased the molar ratio of phytate to Fe (19.70–33.67% and 31.55–45.77%) in brown rice and polished rice, increasing iron bioavailability. Our findings indicate that Fe2O3 NPs can be effectively applied as a foliar fertilizer to enhance rice yield, quality, and iron nutrition.