Abstract: Characteristics of CH₄ and N₂O emissions from wheat fields applied with pig manure in combination with chemical fertilizers were studied using the static chamber method and gas chromatography, and greenhouse effect of the CH₄ and N₂O emitted from the fields were assessed using global warming potentials (P_GW). Results show that the average CH₄ flux from Treatment NPK (the plots applied with chemical fertilizer as in conventional practice), Treatment NPKS (the plots applied with chemical fertilizer plus straw), Treatment 50% PM (the plots applied with half pig manure and half chemical fertilizer) and Treatment 100% PM (the plots applied with pig manure only) was 6.10, 10.26, 5.32 and 2.35 μg•m^-2•h^-1, respectively, the average N₂O flux from Treatments NPK, NPKS, 50% PM and 100% PM was 24.25、38.24、12.21 and 16.06 μg•m^-2•h^-1, respectively. It was found that CH₄ flux increased with temperature after the elongation stage, and N₂O emissions occurred mainly after irrigation or rain during the seeding stage. Compared to Treatment NPK, Treatment NPKS was 57.9% and 52.0% higher in P_GW and P_GW per yield, respectively, while, Treatment 100% PM was 34.3% and 26.0% lower and Treatment 50% PM 48.9% and 48.9% lower in P_GW and PGW per yield, respectively.However,compard with Treatments NPK and NPKS,Treatment 100% PM was significantly lower in wheat yield. It is, therefore, concluded that Treatment 50% PM, that is, to replace half of the rate of chemical fertilizer applied in conventional practice with pig manure, is a good option to reduce CH₄ and N₂O emissions from wheat fields without significant yield reduction.

Key words: manure, chemical fertilizer, greenhouse gas, wheat