Soil & nature cycles · Decomposed soil organic matter
What is humus?
Puschel looks for finished woodland soil and finds something that keeps changing.
The short answer
Humus is greatly changed material from dead living things, such as old leaves. Soil animals, fungi and bacteria help transform it. Humus can hold water and nutrients in soil.
An imagined Wusel scene
Puschel and Flauschi investigate
An old leaf rests on dark soil beside the path. Puschel“Is that the whole soil?” asks Puschel. Flauschi looks at the little crumbs.
Flauschi“Many things work together here,” she says. Puschel leaves the leaf in place. A good question does not need a pawful of earth.
Puschel“Woodland soil is a story with lots of contributors,” he says. Flauschi nods. Today they remain attentive readers.
Little Wusel quiz
Does soil consist only of humus?
Show answer
No. Soil also contains tiny pieces of rock, water, air and living organisms.
Word help
- humus
- Greatly transformed remains of living things in soil.
- nutrient
- A substance a living thing needs to grow and live.
- mineral
- Here, a mineral nutrient such as potassium. Plants usually absorb these nutrients dissolved in water; they are not ready-made sugar.
Explore in more detail
Here you will find longer explanations and further details. You can explore them together.
Understand step by step
How it works – simply explained
Remains are transformed
Soil organisms process dead leaves and other organic remains, material from living things. A leaf does not instantly become finished soil.
Humus is one part
Strongly transformed organic material contributes humus. Soil also contains mineral particles, air, water and living organisms.
The mixture helps plants
Humus holds water and nutrients and supports crumbly structure with spaces for air and water. Dark colour alone does not prove a particular humus content.
The key points again
Discover
Humus forms when soil organisms break down and change dead plants and other remains of living things. These remains are called organic matter. Humus is the part that has already been greatly changed in the soil.
Understand
Humus is only part of soil. Soil also contains tiny pieces of rock, such as sand and clay, as well as water, air and living organisms.
Connections
Humus can store water and nutrients. Nutrients are substances plants need to grow. Humus also helps soil form loose crumbs with little spaces between them. This is what soil structure means.