In a recent article published in Soil Biology and Biochemistry, Paliaga et al., investigated the impact of 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 on 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 determination using traditional chloroform fumigation methods and a new CO2 high-pressure (CO2HP) technique. Biochar, a charcoal-like material produced from biomass pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More, has gained attention as a soil amendmentA soil amendment is any material added to the soil to enhance its physical or chemical properties, improving its suitability for plant growth. Biochar is considered a soil amendment as it can improve soil structure, water retention, nutrient availability, and microbial activity.   More due to its potential to improve soil functions, enhance microbial activity, and increase crop production. However, biochar’s high sorptive capacity may interfere with traditional methods for determining soil microbial biomass, specifically chloroform fumigation-incubation (FI) and fumigation-extraction (FE).  

The authors compared the effects of two types of biochar, produced at different pyrolysis temperatures, on microbial biomass determination. They found that the presence of biochar significantly influenced the results obtained from both traditional and CO2HP methods. The type of biochar also played a role in the results. The presence of biochar produced at 880°C (B880) resulted in a decrease in ΔCmic values, potentially due to acclimation of microbial biomass to the new habitat. Conversely, the addition of biochar produced at 440°C (B440) increased ΔCmic when determined by the FE method, compared to FI and CO2HP-E methods. This suggests an overestimation of extractable carbon after fumigation, possibly due to the adsorption of chloroform by the B440 biochar, which is rich in functional groups.  

The authors concluded that biochar interfered with the determination of ΔCmic and ΔNmic (microbial nitrogen) as a function of both the type and amount of biochar added. The study highlights the need to consider the potential interference of biochar when using traditional and new methods for determining soil microbial biomass. Further research is needed to develop accurate and reliable methods for assessing microbial biomass in biochar-amended soils.  

SOURCE: Paliaga, S., Laudicina, V. A., Muscarella, S. M., Said-Pullicino, D., & Badalucco, L. (2025). Comparison of different methods for estimating microbial biomass in biochar-amended soils. Soil Biology and Biochemistry, 203, 109733.https://doi.org/10.1016/j.soilbio.2025.109733