What Is Decaying Organic Matter in Soil?

When organisms like plants, humans or other animals die, fungi and bacteria break down their remains. The fungi and bacteria obtain the nutrients and energy they need, and in the process they recycle nutrients into the soil, making them available for plants.

The tissues of living organisms are rich in important nutrients. Your body, for example, contains lots of sugars, proteins, nucleic acids and lipids (fats) that bacteria and fungi can use for their nutrition. Once an organism dies, the defenses it maintained against microorganisms while alive cease to function, so fungi and bacteria start to digest the organism's remains. Wastes like feces also contain a variety of nutrients that decomposers can use.

As fungi and bacteria break up the remains and wastes of other organisms before they too die in their turn, they recycle important nutrients like nitrogen and phosphorus back into the soil. This process of decay enriches the soil so it can sustain more plant life.

In chemistry, the word organic refers to carbon compounds. Since all life is composed of carbon compounds, the chemistry of life is in essence organic chemistry, and organic matter is material that came from a once-living organism. The term organic originated with the 18th-century belief called vitalism, which held that processes in living organisms were fundamentally different from other chemical reactions. This belief has long since been discredited, but the term organic is used up to this day.