A research team led by Zhang Huimin from the Institute of Agricultural Resources and Regional Planning at the Chinese Academy of Agricultural Sciences, recently published a study in the Journal of Cleaner Production shedding light on a groundbreaking strategy for sustainable double rice production. Titled "Green manure substitution reduces carbon and nitrogen footprints and improves net ecosystem economic benefits in double rice systems", the study reveals the significant role of integrating green manure into agricultural practices. By replacing a portion of chemical nitrogen fertilizers with green manure, the study unveils a significant reduction in carbon and nitrogen footprints, and at the same time enhances net ecosystem economic benefits in double rice systems. This provides a new effective strategy for the sustainable production of double rice crops.

Double rice production is crucial for ensuring food security. However, the long-term use of large amounts of chemical nitrogen fertilizers increases carbon and nitrogen footprints, posing environmental pressures and potentially affecting the economic sustainability of the system. Green manure, as a traditional source of organic fertilizer, has potential ameliorative effects in agricultural ecosystems. Yet, its comprehensive impact on carbon and nitrogen footprints and ecological economic benefits in double rice systems remains unclear and requires further exploration.

Based on a long-term field experiment initiated in 2008 at the Qiyang Red Soil Experimental Station of the Chinese Academy of Agricultural Sciences, this study systematically investigated the effects of different treatments on double rice yield, carbon footprint, nitrogen footprint, and net ecosystem economic benefits (NEEB). The research showed that substituting 20% of conventional chemical nitrogen fertilizer with green manure (GN80) achieved the best results. Compared to other treatments, grain yield, harvest index, nitrogen recovery rate, and NEEB increased by 12.2%–99.1%, 3.4%–20.8%, 38.5%–148.0%, and 19.0%–129.0%, respectively. In GN80 and GN60 treatments, there was a strong positive correlation between carbon and nitrogen footprints which could be simultaneously mitigated. Methane emissions and reactive nitrogen losses were the main factors. In contrast, N100 and GN100 treatments exhibited trade-offs. The annual carbon footprint of GN80 was reduced by 24.1% and 28.2% compared to GN100 and GN0, respectively, and the annual nitrogen footprint and related yield-scaled footprints were also significantly lower than other treatments.

This study clarifies the multifaceted benefits of substituting 20% of chemical nitrogen fertilizer with green manure in double rice systems, balancing yield, environmental, and economic benefits. It provides important theoretical and practical references for the green and sustainable development of double rice systems.

Doctoral student Nano Alemu Daba and Associate Researcher Huang Jing from the Institute of Agricultural Resources and Regional Planning at the Chinese Academy of Agricultural Sciences are the co-first authors, with Researcher Zhang Huimin as the corresponding author. The research was supported by the National Key Laboratory of Efficient Utilization of Dryland and Semi-arid Arable Land, the National Natural Science Foundation, the Innovation Project of the Chinese Academy of Agricultural Sciences, the earmarked fund for CARS-22(green manure) and CARS-01(rice), and the Hengyang Station for Comprehensive Observation of Long-term Agricultural Factors. 

Original article link:

https://doi.org/10.1016/j.jclepro.2025.146266