Biochar Addition Effects on Rice Yield and Climate Change from Rice in the Rice–Wheat System: A Meta-Analysis

Biochar application has been recognized as a promising strategy to improve crop productivity while mitigating climate change. However, comprehensive studies examining its effects on rice production and agro-environmental benefits in rice–wheat rotation systems are still limited. To address this gap, we evaluated the impact of biochar addition on rice yield, soil organic carbon (SOC), CH4 emissions, N2O emissions, global warming potential (GWP), and greenhouse gas emissions intensity (GHGI) in rice–wheat rotation system in China using 630 pairwise observations from 56 publications. The results showed that biochar addition increased rice yield by 10.70% (0.1 t ha−1), with the improvements ranging from 9.42% (0.07 t ha−1) to 14.11% (0.13 t ha−1) across different application rates. Biochar addition also enhanced SOC by 30.45%, reduced N2O emissions by 19.88%, and consequently lowered GWP and GHGI by 11.07% and 19.03%, respectively. We further examined the impact of biochar properties (raw materials, initial pH, total nitrogen (TN), and ash fraction) on yield improvement and climate change mitigation. The results indicated that raw materials, TN, and pH of biochar significantly increased rice yield and SOC by 8.19–10.79% and 30.51–34.53%, respectively, as well as reduced N2O emissions, GWP, and GHGI by 20.33–25.60%, 10.76–13.14%, and 19.41–21.60%, respectively. Correlation analysis showed that rice yield initially increased but declined at higher biochar application rates, whereas SOC increased and GWP decreased with rising biochar rates. These findings highlight the potential of biochar to simultaneously enhance yield while mitigating greenhouse gas emissions under high addition rates, providing a practical strategy for promoting green, low-carbon, and sustainable agricultural ecosystems.