Optimizing potassium and nitrogen fertilizer strategies to mitigate greenhouse gas emissions in global agroecosystems.

The efficient management of fertilizer application in agriculture is vital for both food security and mitigating greenhouse gas (GHG) emissions. However, as potassium fertilizer (KF) is an essential soil nutrient, its impact on soil GHG emissions has received little attention. To address this knowledge gap and identify key determinants of GHG emissions, we conducted a comprehensive meta-analysis of 205 independent experiments conducted worldwide. Our results revealed that, in comparison to sole nitrogen fertilizer (NF) application, the concurrent use of KF elevated nitrous oxide (NO) and methane (CH) emissions by 39.5 % and 21.1 %, respectively, while concurrently reducing carbon dioxide (CO) emissions by 8.1 %. The ratio of nitrogen and potassium fertilizer input (NF/KF) is identified as the primary factor explaining the variation in NO emissions, whereas the type of KF plays a crucial role in determining CH and CO emissions. We observed a significant negative correlation between the NF/KF ratio and response ratios of NO and CH emissions and a positive correlation with CO emissions response ratios. Furthermore, our findings indicate that when the NF/KF ratio surpasses 1.97, 4.61, and 3.78, respectively, the impact of KF on reducing NO, CH, and CO emissions stabilizes. Overall, our results underscore that the global integration of KF into agricultural practices significantly influences NO and CH emissions, while simultaneously reducing CO emissions at a large scale. These findings provide a foundational framework and practical guidance for optimizing fertilizer application in the development of GHG emission reduction models.