Abstract:In order to investigate the effect of different irrigation modes of straw return form on N2O emission and yield of paddy field in black soil area, a field experiment was conducted in 2023, which was set up with two irrigation modes, conventional irrigation (F) and controlled irrigation (C), and three types of straw return forms, namely, straw return to the field (S), straw charred to biochar return to the field (B), and straw return to the field through cow’s belly as organic fertilizer (O), and straw not returning (N) as a control group, with a total of eight treatments. The effects of straw return on N2O emission flux and rice yield under different irrigation modes were analyzed. The contents of ammonium nitrogen, nitrate nitrogen, microbial nitrogen and pH value in paddy soil at different growth stages were determined, and the relationship between N2O emission, rice yield and soil environmental factors was analyzed. The results showed that except for the regreening period, the soil ammonium nitrogen content, nitrate nitrogen content and microbial nitrogen content of straw return and organic fertilizer return treatments were increased compared with that of straw non-return treatment. Under the same form of straw return, the average soil ammonium nitrogen content and nitrate nitrogen content during the fertility period of treatments under the controlled irrigation mode were 36.23%~60.82% and 14.16%~19.61% higher than those under the conventional irrigation mode. At the same time, straw return and biochar return can improve the pH value of paddy soil. Under the same irrigation mode, compared with the straw non-return treatment, the total N2O emissions of straw return and organic fertilizer return treatments were increased by 14.44%~24.09% and 8.22%~14.44%, respectively, and the total N2O emissions of biochar return treatment were decreased by 14.31%~23.90%. Biochar return and organic fertilizer return increased rice yield by 3.28%~13.07%, and the yield of biochar return treatment under controlled irrigation mode was the highest. In summary, CB treatment was the ultimate goal of water saving, yield increase and emission reduction.