In a recent meta-analysis published in the journal BiocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More, Kumar et al., explored how biochar amendments affect soil microbial biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More carbon (SMBC) in field experiments. Biochar has gained attention for its potential to improve soil and mitigate climate change. The authors compiled 539 paired observations from various global studies to provide a comprehensive look at biochar’s effects on SMBC.  

The study revealed an overall positive impact of biochar, increasing SMBC by 21.31%. However, the effectiveness of biochar varied significantly depending on several factors. The analysis showed that biochar had the most substantial impact in climates with a mean annual temperature below 15°C and where mean annual precipitation ranged from 500 to 1000 mm. These conditions suggest that biochar is particularly beneficial in cooler, moderately wet regions.  

Soil characteristics also play a crucial role. Biochar application was most effective in soils with coarse and fine textures, alkaline pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More, and specific levels of total organic carbon (up to 10 g/kg), total nitrogen (up to 1.5 g/kg), and cation exchange capacity (below 5 cmol/kg). These findings indicate that biochar can help improve soil health, especially in soils that may be less fertile.  

The type of biochar and how it is applied also matter. Combining biochar with nitrogen fertilizer or manure/compost further enhanced SMBC. However, when biochar was applied with straw, the effect on SMBC was slightly negative. The study identified soil clay proportion, biochar application rate, nitrogen application, and mean annual temperature as the most critical factors influencing biochar’s impact on SMBC.  

In conclusion, this meta-analysis demonstrates that biochar can be a valuable tool for enhancing soil health. However, its effectiveness is highly dependent on various interacting factors, including climate, soil type, biochar properties, and management practices. The authors emphasize the need for long-term field studies across different agricultural systems to optimize biochar use and maximize its benefits.  

SOURCE: Kumar, Y., Ren, W., Tao, H., Tao, B., & Lindsey, L. E. (2025). Impact of biochar amendment on soil microbial biomass carbon enhancement under field experiments: a meta-analysis. Biochar, 7(2), 1-16.