Summary To evaluate the benefits of application of biochar to coastal saline soil for climate change mitigation, the effects on soil organic carbon (SOC), greenhouse gases (GHGs) and crop yields were investigated. Biochar was applied at 16 t ha−1 to study its effects on crop growth (Experiment I). The effects of biochar (0, 3.2, 16 and 32 t ha−1) and corn stalk (7.8 t ha−1) on SOC and GHGs were studied using 13C stable isotope technology and a static chamber method, respectively (Experiment II). Biochar increased grain mass per plant of the wheat by 27.7% and increased SOC without influencing non‐biochar SOC. On average, 92.3% of the biochar carbon and 16.8% of corn‐stalk carbon were sequestered into the soil within 1 year. The cumulative emissions of CO2, CH4 and N2O were not affected significantly by biochar but cornstalk application increased N2O emissions by 17.5%. The global warming mitigation potential of the biochar treatments (−3.84 to −3.17 t CO2‐eq. ha−1 t−1 C) was greater than that of the corn stalk treatment (−0.11 t CO2‐eq ha−1 t−1 C). These results suggest that biochar application improves saline soil productivity and soil carbon sequestration without increasing GHG emissions.

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