Effect of biochar application on yield, soil carbon pools and greenhouse gas emission in rice fields: A global meta-analysis
Shenglin Wen, Ningbo Cui, Yaosheng Wang, Daozhi Gong, Zhihui Wang, Liwen Xing, Zongjun Wu, Yixuan Zhang
Abstract
Biochar is applied worldwide as an effective tool for improving rice yield and increasing soil carbon pools while contributing to greenhouse gas emission reduction. However, there is a knowledge gap concerning the effects of biochar application on rice yield, soil carbon pools, and greenhouse gas emissions in rice fields under varying environmental conditions. Therefore, we conducted a comprehensive meta-analysis of 1827 observations from 134 studies to identify the key factors influencing rice yield, soil carbon pools, and greenhouse gas emissions, and to determine their impact pathways using structural equation modeling (SEM). Results showed that biochar application significantly increased rice yield, soil organic carbon (SOC), soil carbon to nitrogen ratio (C:N ratio), and microbial biomass carbon (MBC) by 16.0 %, 37.7 %, 31.8 %, and 16.3 %, respectively, while reducing methane (CH 4 ) emission, nitrous oxide (N 2 O) emission, global warming potential (GWP), and dissolved organic carbon (DOC) by 5.2 %, 14.4 %, 8.6 %, and 2.5 %, respectively. Straw-derived biochar, produced via pyrolysis at temperatures below 450 °C with the application rate of 10 t ha −1 , proved to be an effective method for improving rice yield and soil carbon pools while reducing greenhouse gas emission. The SEM analysis revealed a direct positive relationship between soil properties (soil total nitrogen, soil organic carbon and pH) and rice yield, with a standardized path coefficient of 0.158 ( P < 0.01). Moreover, climate conditions (mean annual air temperature (MAT) and mean annual precipitation (MAP)) had direct positive impact on N 2 O emission and GWP, with standardized path coefficient of 0.28 ( P < 0.01) and 0.179 ( P < 0.05), respectively. Biochar application is more effective for soils with SOC <10 g kg −1 and pH >8, particularly in temperate regions with MAT >15 °C. Our findings provide valuable insights into optimizing biochar application strategies to balance trade-offs between rice yield, soil carbon pools, and greenhouse gas emissions.