Effects of diatomite application on the rice yield, methane emission, and temperature sensitivity of methane emission of ratooning rice

Understanding the effects of nitrogen (N) fertilizer and diatomite application on methane (CH₄) emissions and the temperature sensitivity (Q₁₀) of CH₄ emissions of the ratooning rice system is crucial for optimizing greenhouse gas emissions from paddy ecosystem. In this study, a two-year field experiment was conducted from 2022 to 2023 in Jingzhou City, Hubei Province. Three treatments were established at the study site of the ratooning rice: no nitrogen fertilizer application (CK), nitrogen fertilizer application (N), and combined application of nitrogen fertilizer with diatomite (N+Si). The CH₄ fluxes were measured using a closed-chamber method, and the rice yields and soil properties were also observed. The results showed that, compared with the CK treatment, both the N and N+Si treatments significantly increased the rice yields during the main and ratoon seasons (P<0.05). Moreover, the rice yield in the main season was 3.75%−3.85% (P<0.05) higher under N+Si treatment than that under N treatment. The cumulative CH₄ emissions of the entire growth period (the main and ratoon seasons) under both N and N+Si treatments were significantly higher than that under CK treatment (P<0.05). However, in 2022 and 2023, the N+Si treatment significantly reduced the cumulative CH₄ emissions by 25.99%−38.66% (P<0.05) in the entire growth season relative to that under N treatment. Consequently, the N+Si treatment had significantly reduced the CH₄ emissions per unit yield in both the main by 26.52%−43.51% (P<0.05). In ratoon seasons, CH₄ emissions per unit yield under N+Si treatment decreased by 18.65% in 2022 and 41.14% (P<0.05) in 2023, respectively, compared with N treatment. Correlation analysis revealed that the influences of soil properties on the CH₄ emission flux were quite different among the various treatments and rice growing seasons. The CH₄ emission flux significantly decreased with the soil redox potential (P<0.05) in the main season. However, in the ratoon season, the CH₄ emission flux significantly increased with soil temperature and soil NH₄⁺-N (P<0.05). The CH₄ emission flux was also significantly positively influenced by the soil temperature during continuous flooding period in the main season. The N+Si treatment had the highest soil temperature sensitivity of CH₄ emission (Q₁₀ = 8.86), indicating that the addition of diatomite rendered CH₄ emission flux more sensitive to temperature changes. In conclusion, the combined application of N fertilizer and diatomite not only increases the rice yield of ratoon system but also effectively reduces CH₄ emissions from the ratooning system, making it a sustainable fertilizer management strategy.