Appropriate application of zinc oxide nanoparticles reduces soil N2O emissions

Purpose The chemical form of zinc is a critical determinant of its behaviour in soil, yet its specific role in regulating microbial nitrogen cycling and nitrous oxide (N 2 O) emissions remains inadequately understood. This study investigated the dose-dependent effects of zinc oxide nanoparticles (ZnO NPs) and zinc sulfate (ZnSO 4 ) on soil N 2 O emissions and microbial nitrogen cycling in the acidic agricultural soil. Materials and methods Gas chromatography and high-throughput sequencing were used to explore the effects of two types of Zn fertilizers (ZnO NPs and ZnSO 4 ) and four additional doses (10, 50, 100, and 500 mg kg − 1 ) on N 2 O emissions in soil from a rice–wheat rotational system. Results and discussion Through controlled microcosm experiments, we demonstrated that the use of ZnO NPs at concentrations ≥ 50 mg kg − 1 significantly reduced cumulative N 2 O emissions (4.33–28.53%). High concentrations (500 mg kg − 1 ) of ZnO NPs inhibited soil ammonia monooxygenase and nitrite reductase activities and reduced the abundance of archaeal ammonia oxidizers (AOA) amoA and nirS genes, and the relative abundance of Nitrososphaerales, which was the key factor leading to a decrease in N 2 O emissions. ZnSO 4 exhibited stronger inhibition (14.1% reduction at 500 mg kg − 1 ) because of its higher zinc ion (Zn 2+ ) bioavailability, highlighting nanoparticle dissolution kinetics as a critical regulatory factor. Soil bacterial microbial community structure under low concentration (10 mg kg − 1 ) of ZnO NPs differed from other treatments. The soil bacterial community structure differed from that in the other treatments under a low concentration (10 mg kg − 1 ) of ZnO NPs. Compared with their bacterial counterparts (AOB), AOA were more sensitive to ZnO NPs, which aligns with the results of pH-dependent niche partitioning in acidic soils. Conclusion Overall, optimal ZnO NPs and ZnSO 4 application mitigated agricultural N 2 O emissions. These findings underscore the potential of strategically applied ZnO NPs to mitigate N 2 O emissions and promote the sustainable use of nanofertilizers.