Optimizing the basal application dosage of ZnO nanoparticles for enhancing rice yield, rice quality, and zinc content

Abstract

Zinc (Zn) oxide nanoparticles (ZnO NPs) have been increasingly utilized in agriculture as an innovative Zn fertilizer, prompting numerous studies to assess their impact on plant growth. However, research on the optimal application methods and dosages of ZnO NPs in rice remains limited. In this study, various basal application dosages (0, 3.75, 7.5, 15, 30 and 60 kg hm⁻²) of ZnO NPs on rice yield, rice quality, and Zn content and distribution in grains were investigated using field experiments in the rice growing seasons of 2022 and 2023. Control experiments were also conducted, including treatments without Zn application and those with ZnSO₄ applied at the same Zn dosage. Results showed that ZnO NP and ZnSO₄ applications led to an increase in rice grain yields in the range of 0.34–0.50 t hm⁻² and 0.06–0.40 t hm⁻², respectively, over the two-year experiment compared to the treatment without Zn application. Furthermore, ZnO NPs improved rice quality by enhancing the head rice rate, reducing chalky grain percentage, and improving taste value and rice breakdown. The application of ZnO NPs significantly elevated Zn content in both milled and brown rice compared with the control. In 2022, Zn content in milled rice increased from 20.79% to 41.67% and in brown rice from 25.20% to 47.31%. In 2023, the increase ranged from 12.18% to 32.18% in milled rice and from 17.68% to 38.66% in brown rice. However, the utilization efficiency of ZnO NPs decreased from 7.02% to 1.26% as the application dosage increased from 3.75 kg hm⁻² to 60 kg hm⁻². Despite this decrease, the utilization efficiency of ZnO NPs remained higher than that of ZnSO₄ at the same Zn dosages. Considering yield, rice quality, Zn fertilizer utilization, and Zn accumulation, a basal application dosage of 7.5–30 kg hm⁻² of ZnO NPs is optimal for improving rice yield, rice quality, and Zn accumulation. This study effectively demonstrated that ZnO NPs could serve as a highly efficient fertilizer for synergistically enhancing rice yield, rice quality, and Zn content in the edible grain fraction.