What is the most abundant gas found in soil?

The most abundant gas found in soil is carbon dioxide. This gas is a byproduct of the decomposition of organic matter, which occurs as soil microorganisms break down plant and animal residues. This process releases carbon dioxide into the soil atmosphere, where it can accumulate due to the confined space.

Soil respiration, performed by living organisms such as bacteria and fungi, contributes significantly to the concentration of carbon dioxide in the soil. This gas is also important for plant growth, as it is used in photosynthesis. While nitrogen is prevalent in the atmosphere and plays a critical role in soil chemistry, its presence in soil gas is much less than that of carbon dioxide. The levels of oxygen can vary based on specific conditions and are generally lower in saturated soils than in the atmosphere. Hydrogen is present in very small amounts in the soil atmosphere, primarily as a trace gas. Thus, carbon dioxide is recognized as the most abundant gas in soil due to its continuous production from organic matter decomposition and soil respiration.