Biochar increases soil microbial biomass but has variable effects on microbial diversity: A meta-analysis

Area of Science:

• Soil Science
• Microbiology
• Environmental Science

Background:

• Biochar is a soil amendment studied for carbon sequestration and soil quality improvement.
• A systematic understanding of biochar's impact on soil microbial biomass and diversity is needed.

Purpose of the Study:

• To systematically analyze the effects of biochar on soil microbial biomass and diversity using meta-analysis.
• To identify factors influencing biochar's impact on soil microbial communities.

Main Methods:

• Meta-analysis of 999 paired data points from 194 studies.
• Analysis of biochar properties, soil properties, and experimental conditions (field vs. lab, duration, rate).

Main Results:

• Biochar significantly increases soil microbial biomass.
• Biochar's effect on microbial diversity is variable and depends on soil properties.
• Low-temperature biochar from nutrient-rich feedstocks showed greater increases in microbial biomass and diversity.
• Increases in microbial biomass were higher in field studies, sandy soils, and when measured by fumigation-extraction (MBC_FE).
• Bacterial biomass increased in lab studies; fungal biomass increased in soils with pH ≤ 7.5 and soil organic carbon ≤ 30 g/kg.
• Microbial diversity increased in acidic, sandy soils with low organic carbon, and in lab incubation studies.
• Long-term, low-rate biochar application consistently increased microbial diversity.

Conclusions:

• Biochar application generally boosts soil microbial biomass.
• Biochar's influence on microbial diversity is context-dependent, particularly on soil characteristics.
• Optimizing biochar properties (low temperature, nutrient-rich feedstock) and application strategies (long-term, low-rate) can maximize benefits.
• Future research should focus on long-term field studies across diverse soil types using standardized methods.