Qian, et al (2024) Converse Responses 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 Application on N₂O Emissions in Soils at Different 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 Values in a Subtropical Citrus Orchard. Agronomy. https://doi.org/10.3390/agronomy14081831

Biochar, 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 known for its potential to mitigate greenhouse gas emissions, shows varied effects on nitrous oxide (N2O) emissions depending on soil pH levels. In a recent study, researchers investigated the impact of biochar on N2O emissions in a subtropical citrus orchard with soils of differing pH values, ranging from highly acidic to neutral (pH 4.0 to 7.2).

The study revealed contrasting results. In highly acidic soils (pH 4.0), biochar reduced N2O emissions, likely due to the enhanced activity of denitrifying bacteria that convert N2O to nitrogen gas. This was attributed to the biochar’s ability to increase soil pH and decrease dissolved organic carbon, which favored the nosZ gene responsible for this conversion.

However, in soils with a pH between 5.1 and 7.2, biochar had the opposite effect, increasing N2O emissions. This was linked to biochar’s influence on both nitrification and denitrification processes. The higher soil pH stimulated ammonia-oxidizing bacteria (AOB) and denitrifying genes (nirK, nirS), contributing to increased N2O production. In these soils, biochar raised levels of dissolved organic nitrogen and carbon, further enhancing N2O emissions.

The study underscores the importance of considering soil pH when applying biochar as a strategy to mitigate N2O emissions in agricultural systems. While biochar can effectively reduce emissions in highly acidic soils, its application in less acidic soils may lead to an unintended increase in greenhouse gas emissions.