[Effects of Biochar and Straw on Soil N₂O Emission from a Wheat Maize Rotation System]

The effects of biochar and straw return on soil N₂O emissions were studied in the winter wheat-summer maize rotation system of intensively farmed land in North China to provide a theoretical basis for N₂O emission reduction and the efficient straw utilization. The experiment included the following four treatments:① Control (CK); ② Biochar application at a rate of 9.0 t·(hm²·a)^-1 (C); ③ Straw return (SR); and ④ Straw return plus biochar application at a rate of 9.0 t·(hm²·a)^-1 (C+SR). The results showed that in the wheat season, the CK treatment showed a slight decrease in soil N₂O emission while the SR and C+SR treatments promoted soil N₂O emission by 47.4% and 71.8%, respectively. In the maize-growing season, the CK treatment reduced soil N₂O emission by 29.8% while the SR and C+SR treatments increased soil N₂O emission by 13.4% and 35.8%, respectively. During the wheat-growing season, the soil water, NH₄⁺-N, and MBN content were the main environmental factors affecting N₂O emissions; during the maize-growing season, NO₃^--N, NH₄⁺-N, and MBC content were the main environmental factors affecting emissions. Based on our results, the application of biochar to cropland is an effective option for mitigating greenhouse gas emissions, whereas direct straw return to fields might not be an effective strategy. More research is now needed to examine the effect of the return of straw of different maturity on N₂O emissions.