Influence of biochar on soil air permeability and greenhouse gas emissions in vegetated soil: A review

Abstract

The increasing emission of greenhouse gases such as CO₂, CH₄, and N₂O from the soil has become a growing concern globally. To address this issue, biochar has emerged as an environmentally friendly soil amendment that can affect the gas permeability of soil and reduce greenhouse gas emissions. The biochar-soil-plant system exhibits a complicated interaction that promotes plant productivity and root elongation, further impacting greenhouse gas emissions. The objective of this paper is to provide a comprehensive review of the effects of biochar on soil gas permeability and consequently greenhouse gas emission in vegetated soil. The paper begins by discussing the basic characteristics of biochar and its impact on soil microstructure. It then explores the impact of biochar on the gas permeability of both non-vegetated and vegetated soil. The mechanisms through which biochar influences greenhouse gas emission are explained in terms of modified soil aeration, water holding capacity, adsorption, pH, available nutrients, and the activity of soil microbes and enzymes. The role of plants in greenhouse gas emission in biochar-amended soil is also analysed by comparing the vegetated group with the non-vegetation group. The paper includes a discussion of the various methods used to measure soil gas permeability, such as the steady-state and transient methods, as well as greenhouse gas emission measurement techniques, such as the chamber system and micrometeorological methods. Finally, future research directions are proposed to highlight the impact and corresponding mechanisms of plant roots on the biochar-induced variation of soil gas permeability and greenhouse gas emission.