Humus: definition, effect & everything important

What exactly is humus and how does it affect plants? You can find these and other answers on the subject of hummus here.

Even many experienced gardeners are wondering what humus actually is. The answer to this question is actually quite simple: humus is the dead organic matter in our soil. Because of its positive influence on plant growth, it is also referred to by many gardeners as the "black gold of the garden". In this article we will go into more detail and explain what hummus is and how it is formed.

What is hummus?

Humus is the part of soil that forms from dead organic matter. Put simply, material that once lived in or on the ground and then died. Not only plant parts such as leaves or roots, but also animal remains, dead insects or fungi and bacteria contribute to this organic substance in the soil.

How does humus affect plants?

Humus in the soil is a real miracle cure. Due to its stable, crumbly structure, it loosens heavy soil so that plants can root better in it. In addition, the roots are better aerated. Light, sandy soils usually store little water. Humus molecules, on the other hand, absorb a lot of water - they literally swell. Consequently, for example, a sandy soil with a high humus content can store much more water than an equally sandy soil with a low humus content. For the hobby gardener, this means less watering is necessary. In addition, humus can store nutrients and make them available for the plants. As it breaks down, even more nutrients are released, allowing your garden soil to even make up for missed fertilizers.

Together with clay, which is also present in many soils, humus forms stable, three-dimensional Compounds that prevent your soil from compacting too quickly when walked over or moves. Of course, this also benefits your plants, which often do not like it at all when their roots suffer from waterlogging or a lack of oxygen due to compacted soil.

Due to the dark brown to black color of humus in the soil, it also warms up faster in spring, so that plants can germinate earlier and start growing faster.

Last but not least, a sufficient humus content is essential for healthy soil life. The soil organisms, which often live together with your plants for mutual benefit, need humus as a basis for life and in return provide nutrients for the garden.

Formation of humus: humification

Humus consists of so-called "humic substances". Depending on the conditions under which it was formed, it is composed differently. The process of humification is so complex and the components of humus so different and variable that it has not yet been possible to completely explain the underlying process explore. However, some circumstances are considered certain:

Not only many chemical and biological processes are involved in the formation of humic substances, but also the inhabitants of our soils involved: earthworms, bacteria, fungi, the smallest insects and sometimes even supposed pests such as moles or voles.

They carry out the first step in the formation of humus: they crush, eat, digest and transport the dead material that they find in the soil as a kind of "garbage disposal". After this initial crushing, many steps of humification occur without the involvement of soil-dwelling microorganisms.

Some materials decompose more slowly than others: sugars or starches, which are also found in leaf litter or Root residues can be found are easily decomposed and are broken down faster than, for example proteins. The decomposition of pectins, the "glue" between the plant cells, takes a little longer. Cellulose, which forms the cell walls, breaks down even more slowly. After all, it takes quite a long time for lignin, the so-called "wood matter" of microorganisms, to be broken down. This can be seen from the fact that in the forest, in the thick, half-rotted layer of leaves, there are still "leaf skeletons" and small twigs that contain a lot of lignin.

During degradation, molecular fragments are repeatedly released from the decomposing material. These large molecules can change, parts can be split off or other parts can be added. So there are numerous chemical processes taking place. Eventually, they can reassemble and form so-called "macromolecules", which are then called "humic substances".

It is not possible to create a general chemical formula or an animation of such a humic substance, because its composition is always different. They can only be classified into three groups according to their properties:

• The "fulvic acids" contain smaller, strongly acidic molecules with a yellow to red-brown color, which are mainly formed in acidic, nutrient-poor soils such as in coniferous forests.
• The "humic acids" form larger molecules, are brown-black in color and slightly acidic. They are mainly formed in slightly acidic or neutral soils where soil organisms are active, for example in your garden soil.
• The "humins" are the largest humic substance molecules, are deep black in color and very slightly acidic. They are found in all soils.

Through various processes, including the connection of the resulting humus molecules with charged ones Calcium ions or other soil minerals are what create the large, visible humus flakes that you see on a compost heap Can be found.

Humic substances are in themselves very difficult to break down again. But a fundamental change in the environmental conditions can also be made possible.

humus formation and mineralization

When the organic matter in the soil turns into humus, it is called "humification". However, all the dead material can also be converted in another way, namely by “mineralizing” it.

Put simply, the term "mineralized" means that all of these leaves, bits of root, and dead soil critters are broken down into their individual atomic or molecular parts. Every nutrient that a living being has once ingested and from which it consisted is released again, gets into the soil and can be used again by other living beings.

The mineralization of organic matter in the soil is carried out entirely by microorganisms living in the soil. They break down the organic matter and use some of it as food. The large organic building blocks practically “disappear” – the carbon escapes as CO₂ into the air, minerals go into the soil solution.

This type of "recycling" always moves in cycles in nature and saves everyone Hobby gardeners naturally use a lot of fertiliser, because the minerals that are released can be used by the plants serve nutrients. Of course, no useful humus is formed during the mineralization of organic material, and the humus itself can also be broken down by mineralization.

So there are two possibilities for the undecomposed organic material in the soil: complete mineralization or partial decomposition with subsequent humification.

humus economy

Mineralization is a useful thing because it provides plant nutrients. Humification is also important because the humus that is formed improves the soil properties, as can be read in the section above.

We shouldn't want just one or the other for our soil, our goal is a balanced relationship – with a sufficient humus content. The influencing of this ratio is referred to as "humus economy".

It is possible to influence the relationship between humification and mineralization via the amount and type of material added to the soil. In addition, the activity of the organisms living in the soil can also be changed. Depending on the type of soil and the type of cultivation, there are many ways for you as a "soil owner" to operate a "humus economy" that maintains or even increases your soil humus content. Read for more detailed information and practical application tips humus economy here further.

Buying hummus: you need to pay attention to this

Humus formation is a lengthy, natural process that requires a lot of patience. If you want it to go a little faster, you can sort of buy hummus and distribute it where you need it. You can purchase hummus in this way:

• As compost from the recycling center
• As potting soil in sacks
• From the compost heap of a garden owner friend

Remember that hummus is a natural product. In particular, the properties of compost are very variable, depending on the raw materials and rotting conditions. The compost from the recycling center must be within certain legal limits, and the potting soil also meets the manufacturer's standards. Here we have all the detailed information about Buying humus summarized for you in our special article.

If you want to keep the humus you just bought, you have to protect it from degradation and continue to encourage the build-up of new humus. For this you can use the tips from the article on humus economy to use.