Enhancing nitrogen transformation and humification in cow manure composting through psychrophilic and thermophilic...

Excessive nitrogen release during composting poses significant challenges to both the environment and compost quality. Biological enhancement of humification and nitrogen conservation is an environmentally friendly and cost-effective approach to composting. The aim of this study was to develop a psychrophilic and thermophilic nitrifying bacterial consortium (CNB) and investigate its role in nitrogen transformation and humification during cow manure composting. Analysis revealed that CNB inoculation promoted microbial proliferation and metabolism, significantly increased the number of nitrifying bacteria (p < 0.05), and elevated the activity of nitrite oxidoreductase and nxrA gene abundance. Compared to the control, CNB inoculation promoted the formation of NO₃^--N (77.87-82.35 %), while reducing NH₃ (48.89 %) and N₂O (20.05 %) emissions, and increased humus content (16.22 %). Mantel analysis showed that the higher abundance of nitrifying bacteria and nxrA facilitated the nitrification of NH₄⁺-N. The improvement in nitrite oxidoreductase activity promoted NO₃^--N formation, leading to increased humus content and enhanced compost safety.