Which gas is found in higher concentration in soil compared to air?

Carbon dioxide is found in higher concentration in soil compared to air primarily due to the respiratory processes of soil microorganisms and plant roots. In the soil, organic matter is broken down by microbes during decomposition, a process that produces carbon dioxide as a byproduct. Additionally, plant roots respire, releasing more carbon dioxide into the surrounding soil.

While air consists of approximately 0.04% carbon dioxide, soil can contain significantly higher concentrations, sometimes reaching several percent. This build-up occurs because the soil's physical properties, such as its structure and porosity, limit the rate at which gases can diffuse into and out of the soil. The high concentration of carbon dioxide in the soil is crucial for various soil health functions, including the promotion of nutrient availability and the stimulation of microbial activity, which play essential roles in soil ecology and plant growth.