The Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS), Qiyang Red Soil Station, has conducted research on the characteristics of greenhouse gas (GHG) emissions in double- rice cropping fields under long-term of organic and/or inorganic fertilization, as well as their relationship with soil nutrient ratios.

The findings provide a scientific basis for optimizing fertilization to achieve soil nutrient concentration, net ecosystem carbon budget (NECB) and emission reduction in red soil areas with double- rice cropping fields. The research results have been published in the journal "Agriculture, Ecosystems and Environment".

Rice fields are one of the major sources of greenhouse gas emissions. How to enhance soil fertility and reduce GHG emissions through the rational application of organic and inorganic fertilizers has always been a serious issue. Based on a long-term field experiment on the application of organic and/or inorganic fertilizers in rice fields at the Qiyang Station since 1982, this study dynamically monitored annual greenhouse gas emissions, quantitatively assessed NECB, and analyzed the relationship with soil nutrient ratios. By using ideal solution similarity preference ranking technique, the study recommended reasonable methods for the combined application of organic and inorganic fertilizers.

The research results show that compared to the application of nitrogen-phosphorus-potassium (NPK) or organic fertilizer alone (M), different combinations of organic and inorganic fertilizers (NPKM and PKM) increased GHG emissions. But PKM produced lower GHG emissions than NPKM.  However, both PKM and NPKM treatments improved rice yield, as well as the ratios of soil carbon-nitrogen (C:N), carbon-phosphorus (C:P), and nitrogen-phosphorus (N:P). In the early rice season, the C:P ratio and greenhouse gas emission intensity were negatively correlated with CH₄ and N₂O emissions, while rice yield and CH₄ emissions were positively correlated with global warming potential. In the late rice season, greenhouse gas emission intensity was negatively correlated with CO₂ and CH₄ emissions, and N₂O was positively correlated with global warming potential. The levels of CO₂ and N₂O emissions were higher in the late rice season, but the contribution of CH₄ emissions in the early rice season to the annual global warming potential was greater. Based on the optimization analysis using ideal solution similarity preference ranking technique, organic fertilizer combined with reduced nitrogen application (PKM) was identified as the best fertilization method to increase yield and reduce GHG emission and negative environmental impact, followed by NPKM, NPK, and M treatments.

Md Ashraful Alam, a doctoral student at the Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, and Associate Researcher Huang Jing from Qiyang Station are the co-first authors of the paper, with Researcher Zhang Huimin as the corresponding author. This research was supported by the China Postdoctoral Science Foundation, the Special Project of Jinggangshan High-tech Demonstration Zone, the National Natural Science Foundation of China, and the National Key R&D Program.

Paper Link: https://doi.org/10.1016/j.agee.2023.108695