Effects of agricultural wastes on greenhouse gas emission and global warming potential in black soil

Objective  To study the effects of cow dung, chicken manure, and corn straw combined with chemical fertilizers on greenhouse gas emission and global warming potential.

Method  We used the static chamber technique and set up five treatments including control, chemical fertilizers only, cow dung plus chemical fertilizers containing 50% nitrogen of the total nitrogen in the treatment, chicken manure plus chemical fertilizers with 50% nitrogen, and straw plus chemical fertilizers with 90% nitrogen. Totally 240 kg·hm^–2 nitrogen was applied in each treatment except for control.

Result  Among all treatments, the straw treatment resulted in the highest average emission flux and average total emission of CO₂, being 388.96 mg·m^–2·h^–1 and 14 718.97 kg·hm^–2 respectively. Nitrogen topdressing evidently promoted CO₂ emission. The treatment of chemical fertilizers only resulted in the highest average absorption flux and average total absorption of CH₄, being 0.042 mg·m^–2·h^–1 and 1.36 kg·hm^–2 respectively, and resulted in the highest average emission flux and average total emission of N₂ O, being 0.153 mg·m^–2·h^–1 and 5.75 kg·hm^–2 respectively. The global warming potential in the straw treatment was significantly higher than those in other treatments. The global warming potential in the cow dung treatment was lower than that in the treatment of chemical fertilizers only, yet the difference was not significant.

Conclusion  Straw coverage can increase CO₂ emission in black soil. Upland soil is an important sink of CH₄ in the air. Compared with chemical fertilizers only, organic manure combined with inorganic fertilizer can reduce N₂O releasing. The contributions of different agricultural wastes to atmospheric warming vary in degree.