Abstract: 【Objective】The global warming potential of agro-ecosystem is an important part of affecting global climate change. This study clarified the effects of biochar and straw application on the global warming potential of farmland through field experiments, in order to provide theoretical basis for mitigating climate change and agricultural waste resource utilization. 【Method】In our study, a three-year field positioning experiment was carried out in the winter wheat-summer maize rotation farmland in the Agro-ecosystem Experimental Station in Huantai County, Shandong Province. Four treatments were set up in the experiment: ① control (CK); ② biochar (C); ③ straw return(S); ④ straw return combined with biochar (CS). The nitrogen, phosphorus and potassium fertilizers were applied in all treatments. The nitrogen fertilizer was 200 kg·hm^-2·a^-1 urea, the phosphate fertilizer was 55 kg·hm^-2·a^-1 superphosphate and the potassium fertilizer was 40 kg·hm^-2·a^-1 potassium sulfate. We measured the flux of greenhouse gases (CO₂, N₂O and CH₄) by static chamber-gas chromatography method, calculated the net global warming potential (NGWP) and greenhouse gas emission intensity (GHGI), and analyzed the effect of biochar and straw on the greenhouse gas emissions and the net global warming potential. 【Result】(1) From the emission of greenhouse gases in the three-year experiment, the average annual cumulative Re emissions of S and CS treatments increased by 47.8% and 72.3% (P<0.05), respectively, compared with CK. The average annual cumulative N₂O emission under C treatment reduced by 20.3% than CK treatment (P<0.05), and the cumulative N₂O emission under S and CS treatments increased by 23.6% and 41.4% (P<0.05), respectively. (2) In comparison with CK treatment, soil organic carbon change (ΔSOC) of C, S and CS treatments increased significantly, and the largest increase was in the CS treatment by 150.6% (P<0.05). Compared with the first year, soil organic carbon change (ΔSOC) of C, S and CS treatments increased by 21.7%, 20.8% and 17.8% (P<0.05), respectively. There were significant differences in net global warming potential (NGWP) and greenhouse gas emission intensity (GHGI) among all treatments. Compared with CK treatment, the average annual NGWP of C, S and CS treatments decreased by 163.5%, 171.7% and 273.0% (P<0.05). Compared with the first year, the NGWP of C, S and CS treatments in the third year decreased by 73.4%, 58.8% and 54.7% (P<0.05), respectively. The annual average GHGI of C, S and CS treatments decreased by 236.2%, 253.3% and 388.9% than CK treatment (P<0.05), respectively. In comparison with the first rotation, the GHGI of C, S and CS treatments in the third rotation decreased significantly by 126.3%, 98.2% and 108.6% (P<0.05), respectively. The yield of C, S and CS treatments remained stable with a slight increase, but there was no significant difference between the yield of CK, C, S and CS treatments. 【Conclusion】Compared with applying chemical fertilizer alone, the methods of adding biochar, straw return and straw return combined with biochar could prevent the net global warming potential without reducing crop yield. Among these treatments, straw return combined with biochar could reduce the net global warming potential to the greatest extent. Therefore, straw return combined with biochar is an effective measure to enhance carbon sequestration and mitigate climate change.

Key words: biochar, straw return, greenhouse gas, winter wheat-summer maize rotation, soil organic carbon, net global warming potential (NGWP), greenhouse gas emission intensity (GHGI)