What is the primary natural contributor to organic matter in soil?

The primary natural contributor to organic matter in soil is vegetation. Plants, through their growth, play a crucial role in adding organic material to the soil. This occurs as they shed leaves, die, and decompose. The decomposition process, carried out by microorganisms, transforms the plant material into humus, which significantly enriches the soil's organic content.

Organic matter is vital for soil health as it improves soil structure, increases its water retention capacity, enhances nutrient availability, and supports a diverse ecosystem of soil organisms. While wind, water, and glaciers can contribute to changes in soil structure or nutrient distribution, they do not directly add organic material in the same way that vegetation does. Thus, vegetation is the primary source that continuously contributes organic matter, making it fundamental to soil fertility and overall ecosystem function.