A global assessment of the long-term effects of biochar application on crop yield

The impact of biochar application on crop yield has always been a topic of concern. However, most current research focuses on the short-term effects of biochar on crop growth. Investigating the long-term effects of biochar in increasing crop yields is crucial for food security and sustainable agricultural development. To address this issue, this study performed a coupling of meta -analysis and structural equation model (SEM) based on the establishment of a dataset containing 981 sets of observations. The results demonstrated that biochar significantly and durably boosted crop yield, and biochar also has shown an average increase of 36.2% in SOC over a monitoring period exceeding 2 years. Crop yields increased by an average of 16% after biochar application for the long-term scale, although the increase varied across crop types, and biochar application performed better on corn and wheat than paddy rice production. It is noteworthy that the yield still increased by 15% on average after 6 years of biochar application. According to SEM, the yield increase was positively correlated with the application amount of biochar, and the yield increase was higher under low nitrogen (N) input than under high N input. The long-term yield -increasing effect of biochar was more attributable to its enhancement of SOC rather than its effects on soil bulk density and pH.