Impact of co-introduction of soluble potassium and nitrogen on methanotrophs

Abstract

Aerobic methane (CH₄) oxidation in paddy fields is a critical process for mitigating fugitive CH₄ emissions. Potassium (K) fertilizer is commonly used to increase crop yields and quality in paddy fields, often in combination with nitrogen (N) fertilizer. However, the impact of the significant input of K and N on methanotrophs is unclear. This study employed zeolite-adsorbed K and N to examine their influence on methanotrophic activity. Control groups with non-adsorbed (R) and experimental groups with K alone (K0), and combined with nitrate (NO₃^–-N) (K1) or ammonium (NH₄⁺-N) (K2) were established. Incubations were conducted over six cycles with a 15 % volume ratio of CH₄ and oxygen. Results showed that both K and NO₃^–-N enhanced the abundance of Type I methanotrophs, with K particularly increasing the abundance of Methylomonas and NO₃^–-N primarily promoting the growth of Methylocaldum. Metabolomic analysis indicates K inhibits the synthesis of bioactive and reductive phenols, ketones, sesquiterpenoids, and unsaturated fatty acids. This effect was suggesting that K more readily entering the periplasmic space to stimulate adenosine synthesis, thereby energizing the soluble methane monooxygenase (sMMO) enzyme unique to Methylomonas. N contributes to energy metabolism by integrating into nitrogenous precursors, supporting community vitality. This study provides insights into the adaptation of methanotrophs in ecological niche differentiation and the co-introduction of K and N fertilizer management strategies to alleviate CH₄ emissions