The anaerobic soil volume is a key factor in denitrification, which is a critical process in the nitrogen cycle. Denitrification occurs in anoxic microsites and is influenced by factors such as soil structure, organic matter, and water content. The anaerobic soil volume, or the volume of soil without oxygen, is crucial for denitrification activity, as it determines the availability of oxygen for microbial processes. Recent studies have shown that denitrification hotspots are often associated with particulate organic matter (POM) and are influenced by the spatial distribution of air-filled pores and organic residues. The anaerobic soil volume can be estimated using various methods, including X-ray CT scans and oxygen sensors, which help in understanding the microstructure of the soil. The concept of the anaerobic soil volume has evolved over time, with new techniques allowing for more accurate measurements of oxygen availability and denitrification activity. The review highlights the importance of considering the anaerobic soil volume in denitrification models, as it can significantly affect the prediction of nitrogen oxide emissions. The study also emphasizes the need for further research to improve the accuracy of denitrification models by incorporating the anaerobic soil volume and its relationship with soil properties. The findings suggest that the anaerobic soil volume is a critical factor in denitrification, and its estimation is essential for understanding and predicting nitrogen oxide emissions in soil systems.The anaerobic soil volume is a key factor in denitrification, which is a critical process in the nitrogen cycle. Denitrification occurs in anoxic microsites and is influenced by factors such as soil structure, organic matter, and water content. The anaerobic soil volume, or the volume of soil without oxygen, is crucial for denitrification activity, as it determines the availability of oxygen for microbial processes. Recent studies have shown that denitrification hotspots are often associated with particulate organic matter (POM) and are influenced by the spatial distribution of air-filled pores and organic residues. The anaerobic soil volume can be estimated using various methods, including X-ray CT scans and oxygen sensors, which help in understanding the microstructure of the soil. The concept of the anaerobic soil volume has evolved over time, with new techniques allowing for more accurate measurements of oxygen availability and denitrification activity. The review highlights the importance of considering the anaerobic soil volume in denitrification models, as it can significantly affect the prediction of nitrogen oxide emissions. The study also emphasizes the need for further research to improve the accuracy of denitrification models by incorporating the anaerobic soil volume and its relationship with soil properties. The findings suggest that the anaerobic soil volume is a critical factor in denitrification, and its estimation is essential for understanding and predicting nitrogen oxide emissions in soil systems.