5. Conclusions
Incorporating straw-derived biochar into the fertile paddy soil caused a substantial increase in total soil C and total nitrogen pools and rice biomass. Meanwhile, soil bulk density decreased while rice yield remained unchanged after biochar application. CH4 emissions of biochar treatment were markedly reduced, and CO2 emissions were unchanged throughout the rice-growing season, except for biochar amendment at 29.6 t ha−1. The effects of biocharr addition were not proportional to the application rate. A high rice yield, but with the lowest GHG emission, was achieved with biochar amendment at 29.6 t ha−1. Biochar and N fertilizer can synergistically interact to improve soil C storage and mitigate climate change (total GWP) in fertile paddy fields in the Northeast region.