Humus is predominantly found in the top few inches of soil.
Humus is the dark, organic matter that forms in soil when plant and animal matter decays. This decomposition process is carried out by earthworms, bacteria, fungi, and other microorganisms. Because these organisms are most active near the surface, humus accumulates primarily in the uppermost layer of the soil, known as the topsoil or the "O" horizon (if it is a distinct organic layer).
Here's a breakdown of where you can expect to find humus:
- Topsoil: The most significant concentration of humus is in the topsoil layer. This is where the majority of organic matter decomposition takes place.
- Surface Litter Layer (O Horizon): In some soils, especially in forested areas, there's a distinct layer of decaying organic material on the surface, referred to as the O horizon. This layer also contains humus in various stages of decomposition.
- Agricultural Soils: In agricultural settings, the amount of humus depends on farming practices. Practices that incorporate organic matter (like cover cropping or adding compost) will increase humus levels, while intensive tillage can reduce it.
- Forest Soils: Forest soils are generally rich in humus due to the constant input of leaf litter, woody debris, and other organic materials.
The characteristics of humus include its brown or black color and its loose, crumbly, and spongy texture, all contributing to healthy soil structure and fertility.
