Biochar has the potential to improve soil health, while mitigating climate change by sequestering carbon and reducing greenhouse gas emissions. However, net outcomes vary due to amendment practices, soil properties, and more importantly biochar characteristics. Understanding biochar modulation effects on the soil microbiome is the first vital step to guide precision biochar amendment and biochar design for sustainable agriculture. In this study, we screened 3511 literature records published between January 2018 and April 2020 worldwide, synthesized 3899 observations of 24 microbial responses from 61 primary studies, and performed a three-level mixed-effects meta-analysis that considered moderators including biochar properties (feedstock type, pyrolysis temperature), soil properties (pH, C/N, CEC), and practice conditions (fertilization, application rate, laboratory versus field, observation duration). We found biochar promoted microbial abundance and diversity, and C/N/P-cycling processes. Dehydrogenase activity had the highest increases, followed by cellulase activity, potential nitrification rate, urease activity, microbial biomass carbon (MBC), and invertase activity. Important predictors for biochar performance were feedstock type, pyrolysis temperature, soil pH, fertilization, application rate, and duration. Feedstock type was the most important predictor for the largest number of microbial responses (bacterial PLFA, Shannon diversity, Simpson diversity, β-glucosidase activity, cumulative N2O emission, urease activity), followed by pyrolysis temperature (dehydrogenase activity, acid phosphatase activity, cumulative CO2 emission), and application rate (MBC, urease activity, potential nitrification rate). Soil pH was an important predictor for Chao1 diversity and acid phosphatase activity, fertilization for ammonia oxidizing bacteria abundance and cumulative N2O emission, and duration for potential nitrification rate and acid phosphatase activity. Biochar produced at &lt;350 °C from agricultural biomass, lignocellulose, manure or biosolids was better for enhancing microbial abundance and nutrient-cycling traits. Lignocellulose biochar was the best for suppressing N2O emission. Biochar produced at &gt;350 °C from woody materials was better for maximizing carbon sequestration. Our results suggest biochar feedstocks and production conditions could be tuned to elicit the desired soil microbiome responses and thus ecosystem services.

Modulation effects of biochar on the soil microbiome: A three-level meta-analysis

ACS Fall 2021

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