Phosphate-solubilizing bacterium enhanced nitrification inhibitor efficiency in decreasing soil nitrous oxide...

Nitrous oxide (N₂O) is a potent greenhouse gas, and its emissions are aggravated by the inefficient management of soil nitrogen (N) and phosphorous (P). Effective strategies to reduce N₂O emissions and enhance P bioavailability are critical for improving the efficiency of chemical N and P fertilizers. This study examined the combined effects of nitrification inhibitor dicyandiamide (DCD) and phosphate-solubilizing bacteria (PSB) on N₂O emissions, N-cycling gene abundances, P bioavailability, and phosphatase activities under different soil moisture levels. Compared to the control, DCD reduced AOB amoA gene abundance by 44.3% at 60% water holding capacity (WHC) on day 14, but increased it by 20.1% at 90% WHC on day 28. PSB inoculation increased soil AOA and AOB amoA gene abundances and phosphatase activities but reduced narG gene abundances. At low moisture, N₂O emissions were mainly controlled by nitrification and strongly correlated with AOB amoA on day 14. On day 28, N₂O emissions were negatively related to available P and acid phosphatase activity. These findings suggest that PSB-induced P mobilization acts as a stoichiometric regulator of the N cycle. PSB inoculation enhanced DCD's mitigation efficiency at low moisture by optimizing nutrient stoichiometry and stimulating phosphatase activity. The combined use of nitrification inhibitors and PSB could be an effective strategy to reduce N₂O emissions while improving P bioavailability. This study offers valuable insights into the mechanisms underlying N₂O emissions and N-cycle gene abundances under different N/P management practices and moisture levels, contributing to N₂O mitigation strategies.