A quantitative review of the effects of biochar application on rice yield and nitrogen use efficiency in paddy fields: A meta-analysis

Applying biochar to paddy fields is a helpful approach that potentially increases rice production and nitrogen use efficiency (NUE) to ensure food security and protect the ecological environment. Notwithstanding, reviewing most of the previous experimental studies on the impacts of biochar reveals a considerable inconsistency in the proposed results. The present study conducts a comprehensive meta-analysis on the literature published before February 2021 to investigate the impacts of biochar properties, experimental conditions, and soil properties on rice yield and NUE. The meta-analysis results show that biochar application increases rice yield and NUE by 10.73% and 12.04%, respectively. The most significant improvements in the soil properties are seen in alkaline soils and paddy soils with a fine-textured. In addition, the benefits of biochar are significantly enhanced when produced at 500–600 °C with livestock manure due to the existence of more nutrients compared to other feedstocks. Analysis of water management reveals that biochar application under water-saving irrigation is more effective in increasing rice productivity. In terms of application rates, the >20 t/ha biochar and 150–250 kg/ha nitrogen fertilizer are recommended for improving rice yield and NUE. Regardless of existing uncertainty due to the lack of long-term experimental data, those investigated factors have significant implications for biochar management strategies in rice growth systems.