Objective  Effects of addition of a nitrification inhibitor, dicyandiamide (DCD) or 2-chloro-6 (trichloromethyl) pyridine (NP), on the N₂O and CO₂ emissions and nitrate content in soil and yield and quality of Chinese cabbage grown on the soil in a greenhouse were studied.

  Method   A pot experiment using the soil from a Chinese cabbage greenhouse at Beichakou Village, Daxinge Township, Yongqing County, Langfang City was conducted to grow Chinese cabbage in a static solar greenhouse. A blank control that applied no fertilization (CK) along with 5 treatments that included the addition to the soil of a water-soluble fertilizer (R1), R1(DCD), R1(NP), a liquid sludge nitrogen fertilizer (L), or L(DCD). N₂O and CO₂ emitted from the soils were collected for the determination using static image-gas chromatography. At harvest, nitrate nitrogen in 0–30 cm depth of soil was measured by a flow analyzer, and yield and quality of vegetables grown on the soil recorded.

  Result   The fertilizations significantly increased N₂O emission over CK. However, the addition of nitrification inhibitor reduced the cumulative emission by 45.70% under R1(DCD) and 62.46% under R1(NP) over R1, and that under L(DCD) lower by 45.81% over L. And after topdressing, the cumulative N₂O emission under R1(DCD) became 71.54% and R1(NP) 66.81% lower than those under R1, while that under L(DCD) 37.13% lower than under L. On the cumulative CO₂, it fluctuated after the fertilizations but no apparent effect shown by the inhibitor applications. In the 0–30 cm soil layer, the nitrate nitrogen concentration increased when fertilizerd with increasing depth and decreased with increasing biochemical regulating fertilizers DCD and NP. The nitrification inhibitors improved somewhat the Chinese cabbage quality and yield but not significantly. R1(DCD) and R1(NP) reduced the nitrate content from R1 by 11.10% and 3.41%, respectively, while L(DCD) did by 7.69% over L.

  Conclusion  Biochemical regulating fertilizer improved somewhat the vegetable yield and quality, while reduced the N₂O emissions of the soil benefitting the eco-system.