What does humus mean?
Humus is the stable, dark organic material found in soil, especially in well-drained, biologically active environments. It forms as leaves, roots, organisms, and other organic matter are broken down and transformed by fungi, bacteria, and other decomposers. Unlike undecomposed plant litter, humus is relatively stable and is closely integrated with mineral soil particles. It is valuable because it supplies nutrients, retains water, and improves soil structure and fertility. Gardeners sometimes speak of adding humus when they add compost or other decomposed organic material, although compost and humus are not always identical. The word is especially relevant to soil science, ecology, agriculture, and horticulture, but it can also be used more broadly for any richly decomposed organic matter. Its importance is easy to overlook: the material is often invisible within the soil, yet it helps determine whether soil can store nutrients and support sustained plant growth.
nounA dark, decomposed organic material formed in soil by the gradual breakdown of plant and animal matter. Humus is rich in nutrients and helps soil retain water and support plant growth.
- The stable organic material in soil formed by the decomposition of plant and animal remains.
"The garden's fertile soil was rich in humus, formed from years of accumulating leaf litter."
"Peatlands contain large deposits of partly decomposed plant matter, while mature forest soils may contain well-humified humus."
"Adding compost can increase the amount of humus and improve the structure of sandy soil."
Humus is normally a mass noun and is not normally counted or pluralized.
"The soil contains a rich humus that supports dense plant growth."
Humus is nature's dark pantry: decomposed leaves and organisms become the nutrient-rich matter that feeds new growth.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does humus come from?
Humus comes from the Latin humus, meaning “earth” or “soil,” and was borrowed into English in the 16th century. The Latin word belongs to an Indo-European family associated with the earth, while Latin derivatives such as inhumare, “to bury,” developed a closely related vocabulary around burial and the ground. English humid and humidity also reflect a Latin connection with moisture or dampness, historically associated with earth and moisture.
Related word forms
How humus is actually used
The term is most common in soil science, ecology, horticulture, and gardening. It is normally treated as a mass noun and refers to a material rather than a countable substance.
Easily confused with humus
Humus is the decomposed organic material in soil, whereas humous is an adjective meaning rich in humus or containing humus.