Achieving sustainable rice production through nitrogen-potassium harmony for enhanced economic and environmental gains

In the quest for sustainable, high-yield crop production, achieving the optimal balance between nitrogen (N) and potassium (K) stands as a pivotal goal. We carried out a 3-year field experiment to evaluate the impacts of the combined application of three N rates (90, 120,180 kg N ha−1) and three K rates (120, 160, 210 kg K2O ha−1) on rice yield, fertilizer use efficiency, greenhouse gas (GHG) emissions, global warming potential (GWP), GHG intensity (GHGI), and net ecosystem economic benefits (NEEB) in rice paddy. Our results showed that increasing K under the same N treatment proves beneficial for yield gains (average increase of 4.8 %). Such beneficial effect is also reflected in different N treatments, evidenced by the comparable grain yields between N120 × K160 (9.1 t ha−1) and N180×K120 (9.2 t ha−1). Increasing K significantly enhanced N use efficiency (NUE) through the stimulation of NR, GS/GOGAT, and GDH enzyme activities. This enhancement, along with the strengthened radiation use efficiency (4.7 %), contributed to an overall improvement in grain yield. Compared with N180×K120, both rice varieties, under N120×K160 treatment, showed higher NUE with a 47.6 % increase in PFPN, 12.1 % in NHI, 7.6 % in NUEg, and 9.5 % in NUEb, respectively. Higher NUE also reduced GHGI and improved NEEB. Compared with N180 ×K120 treatment, the GWP and GHGI under N120×K160 treatment decreased by 32.7 % and 31.0 %, while the NEEB increased by $31 ha−1. The composite sustainability scores suggested that the N120×K160 treatment was generally more sustainable compared with other treatments. These findings underscore the significance of optimizing N and K application ratios in rice paddy cultivation, not only for maximizing yields and nutrient use efficiency but also for reducing greenhouse gas emissions and enhancing economic sustainability, ultimately promoting a more environmentally and economically responsible approach to rice farming.