Nitrification inhibitors mitigated reactive gaseous nitrogen intensity in intensive vegetable soils from China

Nitrification inhibitors, a promising tool for reducing nitrous oxide (N₂O) losses and promoting nitrogen use efficiency by slowing nitrification, have gained extensive attention worldwide. However, there have been few attempts to explore the broad responses of multiple reactive gaseous nitrogen emissions of N₂O, nitric oxide (NO) and ammonia (NH₃) and vegetable yield to nitrification inhibitor applications across intensive vegetable soils in China. A greenhouse pot experiment with five consecutive vegetable crops was performed to assess the efficacies of two nitrification inhibitors, namely, nitrapyrin and dicyandiamide on reactive gaseous nitrogen emissions, vegetable yield and reactive gaseous nitrogen intensity in four typical vegetable soils representing the intensive vegetable cropping systems across mainland China: an Acrisol from Hunan Province, an Anthrosol from Shanxi Province, a Cambisol from Shandong Province and a Phaeozem from Heilongjiang Province. The results showed soil type had significant influences on reactive gaseous nitrogen intensity, with reactive gaseous nitrogen emissions and yield mainly driven by soil factors: pH, nitrate, C:N ratio, cation exchange capacity and microbial biomass carbon. The highest reactive gaseous nitrogen emissions and reactive gaseous nitrogen intensity were in Acrisol while the highest vegetable yield occurred in Phaeozem. Nitrification inhibitor applications decreased N₂O and NO emissions by 1.8-61.0% and 0.8-79.5%, respectively, but promoted NH₃ volatilization by 3.2-44.6% across all soils. Furthermore, significant positive correlations were observed between inhibited N₂O+NO and stimulated NH₃ emissions with nitrification inhibitor additions across all soils, indicating that reduced nitrification posed the threat of NH₃ losses. Additionally, reactive gaseous nitrogen intensity was significantly reduced in the Anthrosol and Cambisol due to the reduced reactive gaseous nitrogen emissions and increased yield, respectively. Our findings highlight the benefits of nitrification inhibitors for integrating environment and agronomy in intensive vegetable ecosystems in China.