Biochar and microorganisms combined enhance crop growth and soil properties: Evidence from meta-analysis

Biochar and microorganisms are widely used soil amendments, but the effects of their combined application on crops and soils have not been thoroughly evaluated. We conducted a meta-analysis of 103 studies to examine the effects of biochar-microbe combined (BCM) application on crop physiology ecology and soil function. Together, they significantly improved crop growth and soil properties, with shoot dry weight increasing by 51.79 % and soil organic carbon increasing by 49.38 % compared with the control. BCM application can activate the antioxidant defense system in crops, reduce malondialdehyde levels by 18.24 %, and enhance soil bacterial abundance by 71.9 %. Their effect on soil pH was negatively correlated with the initial soil pH. The effects of BCM application vary with the properties of different biochar sources, pyrolysis temperatures, microbial species, and experiment types. Integrating microbes with low-temperature (≤ 500°C) wood-based biochar showed even better effects, not only enhancing crop growth performance and chlorophyll content, but also producing significant improvements in soil physicochemical properties. The combined application of different functional microorganisms and biochar resulted in varying effects on crop biomass accumulation, growth, and soil quality. In the study, BCM was evaluated for its ecological consequences on crops and soils, and we recommend prioritizing low-temperature biochar in combination with microorganisms to maximize crop and soil improvement.