Identifying the best fertilization practices by many-objective optimization to mitigate nitrous oxide emissions from tea field in the subtropics in Central China

Identifying the best management practices (BMPs) for reducing nitrous oxide (N₂O) emissions in tea field poses challenges due to numerous economic and environmental objectives involved, alongside intricate trade-off relationships amongst them, particularly within the context of climate change. This study proposed a hybrid approach that integrates field observations, the WNMM agroecosystem model, and the NSGA-III optimization algorithm. This integrated method aimed to comprehensively optimize fertilizer application (including rate, type, and method) and nitrification inhibitor addition in order to maximize crop yield potential and minimize N₂O emissions, while also to enhance nitrogen (N) use efficiency (NUE), reduce N loss through leaching and volatilization, and minimize changes in soil organic matter in tea fields of subtropical Central China. The optimized fertilizer application rates based on Pareto fronts for the historical period (1985–2021), SSP2–4.5 (2023–2100) and SSP5–8.5 (2023–2100) are considerably lower than the practices commonly employed by local farmers (450 kg N ha⁻¹). Specifically, the optimized rates meeting the dual objectives of stabling yield (> 3825 kg ha⁻¹) and reducing N₂O emissions (< 4.73 kg N ha⁻¹) are even lower, accounting for 33–38 % of the local rate. Importantly, under the conditions of future climate warming, a combination of intercropping sorghum and deep placement of fertilizers is necessary to realize effective many-objective optimization for N₂O reduction. However, controlled-release fertilizers show a limited effect on N₂O emission reduction. In summary, this study illustrated the significant potential of implementing many-objective optimized management practices to save fertilizer and reduce N₂O emissions without compromising crop yield in tea field. Importantly, the adoption of specific practices such as intercropping sorghum and implementing deep placement of fertilizers can be effective strategies to address climate change-related issues, including N leaching, volatilization, and soil organic matter loss. These findings offer valuable theoretical guidance for tea farmers and local governments.