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Alternate wetting and drying (AWD) is an important strategy that saves water and reduces greenhouse gases emission (GHG). Moreover, biochar (BC) has been also emerged as a promising approach to reduce GHG emissions. Hitherto, the mechanism lying behind reduction in nitrous oxide (N 2 O) emissions following the addition of BC are not clearly understood. Therefore, this field study was performed to assess the effects of different rates of rice straw biochar (RSB), i.e., control (0 RSB), 20 t RSB ha−1, and 40 t RSB ha−1 with no nitrogen (N) fertilizer (-N) and with N fertilizer (180 kg ha−1: +N) on soil pH, soil N dynamics, microbial genes abundance, N 2 O emissions and performance of paddy. The experiment was conducted in two factors factorial design with three replications. Application of RSB enhanced the soil pH and NH 4 + and decreased NO 3 – therefore led to a significant reduction in the N 2 O emissions. However, the application of RSB (40 t ha−1) significantly decreased the N 2 O emissions by +59% and +62% in comparison to control under -N and +N conditions. The increased soil pH augmented the abundance of nosZ and nirK genes, more following addition of 40 t RSB ha−1 and therefore, leads to an appreciable reduction in the N 2 O compared to 20 t RSB and control under both -N and +N conditions. Additionally, 40 t RSB ha−1 significantly enhanced the tillers production, kernel weight, paddy, and dry matter yield compared to control and 20 t RSB ha−1 under -N and +N conditions. Conclusively, RSB application at the rate of 40 t ha−1 could be a promising approach to reduce N 2 O emissions and increase the paddy yield. [ABSTRACT FROM AUTHOR]