Soil denitrification, anammox, and Feammox are key for nitrogen (N) removal in agriculture. Despite potassium (K) fertilizer enhancing N efficiency, their role in regulation of these processes is unclear. A soil column incubation with 15 N isotope tracing was conducted to explore millimeter-scale interactions of N and K on these pathways in soil fertilization zones. After 28 days, individual applications of N and K reduced denitrification-nitrogen removal rate (DNRR), anammox-nitrogen removal rate (ANRR), and feammox-nitrogen removal rate (FNRR) compared to a non-fertilizer control. N fertilizer had a greater effect than K, likely due to the high consumption of dissolved organic carbon by N fertilizer or the increased soil organic matter decomposition by K fertilizer. Combing of N and K increased DNRR, ANRR and FNRR rates by 31 %, 3090 % and 244 % compared to single N, and by-53.7 %, 885 % and 222 % compared to single K. These effects diminished with depth and distance from fertilizer sites. The effects of N fertilizer on these N removal processes might be regulate abundance of key microbes (e.g., Limnobacter and Clostridium ) and key gene (nirK, hzsB, ACM and Geo) by providing N substrates, while K enhances N metabolism efficiency through enzyme activation, indicated by the downregulation of certain genes (hzsB, ACM and Geo) and a negative correlation with N removal by simultaneously increasing gene expression and enzyme activity. These findings provide insights into how N and K together enhance N removal, emphasizing their importance for optimizing this process. (c) 2025 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.