[Effects of Biochar on N₂O Emission from Four Typical Soils in the North China Plain]

As a potential soil conditioner, biochar plays an important role in alleviating greenhouse gas (GHG) emissions. To clarify the influence of biochar on soil N₂O emissions during the winter wheat seedling stage, four typical soils in the North China Plain (paddy soil, shajiang black soil, cinnamon soil, and fluvo-aquic soil) were adopted for field experiments, and four treatments were set:Control (CK), Fertilizer (NPK), Biochar (BC), and Fertilizer+Biochar (NPK+BC). The results showed that fertilization (NPK) significantly increased the N₂O emissions of the four soils. Compared with that of the CK, the N₂O emissions of four soils were increased by 314%, 116%, 240%, and 282%, respectively. The effect of biochar addition on N₂O emissions of the four soils in the North China Plain was different. Compared with that of the CK treatment, the N₂O emissions of paddy soil and cinnamon soil in the BC treatment significantly increased by 72.4% and 50.9%, respectively, whereas the shajiang black soil and fluvo-aquic soil exhibited no significant differences. The combined application of biochar and fertilizer significantly reduced the N₂O emissions of the four soils, compared to that of NPK. The addition of biochar increased the pH of soil. In particular, paddy soil had the lowest initial pH and was most affected by biochar. Fertilization reduced the pH of the four soils. N₂O flux under fertilizer treatment for the shajiang black soil, cinnamon soil, and fluvo-aquic soil was significantly positively correlated with ammonium nitrogen content, whereas N₂O emission fluxes under single biochar treatment on paddy soil and shajiang black soil were significantly positively correlation with nitrate nitrogen content.