Effect of biochar addition on crop yield, water and nitrogen use efficiency: A meta-analysis

Biochar is a widely used soil amendment that has positive effects on improving soil quality, promoting resource efficiency of agricultural production, and reducing environmental pollution. In order to better play the potential role of biochar in agricultural production and optimize the addition strategies of biochar. This study conducted extraction analysis, random forest simulation and win-win analysis on 381 datasets from 63 studies around the world. The results showed that the addition of biochar increased crop yield by 14.45%, water use efficiency (WUE) by 14.28% and nitrogen use efficiency (NUE) by 13.97%. Among them, the key factors affecting the addition effect of biochar were soil organic carbon (SOC), soil total nitrogen (Soil-TN), soil bulk density, biochar carbon content (Biochar-TC) and biochar carbon nitrogen ratio (Biochar-C:N). In addition, the application of biochar with less carbon content (TC ≤ 200 g kg−1, C:N between 50 and 100) in the soil with large bulk density (>1.4 g cm−3) and low nutrients (SOC between 10 and 15 g kg−1, TN ≤ 0.5 g kg−1) could better achieve a win-win situation in crop productivity and resource use efficiency. Our findings can help to formulate the addition strategies of biochar.