Fertilization-induced reactive nitrogen gases and carbon dioxide emissions: insight to the carbon-nitrogen cycles

Different agricultural practices can pose significant threats to environmental quality and human health. This study aimed to assess the emissions of reactive nitrogen (NH3, NOx, and N2O) and carbon dioxide (CO2) induced by fertilization in spinach and cabbage farmlands. Field and pot experiments were conducted to analyze the emission fluxes and intensities of reactive nitrogen gases and CO2. The findings revealed that the total emissions of reactive nitrogen for cabbage and spinach ranged from 21 to 798 kg-N ha−1 and 1.1 to 489 kg-N ha−1, respectively. Generally, organic fertilizers exhibited higher emission intensities of NH3 compared to N2O. While slow-release fertilizers effectively reduced NH3 emissions, they resulted in increased soil N2O emissions. Furthermore, the total emissions of reactive nitrogen from the soil showed a positive correlation with soil CO2 emissions. Particularly, organic farming practices, especially in the case of cabbage, led to increased CO2 emissions from farmlands. Based on the experimental findings, three priority directions were suggested to achieve sustainable soil carbon and nitrogen management in order to minimize emissions from farmlands. This study provides valuable insights for future soil carbon and nitrogen management in subtropical regions.