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

Humus is the dead organic matter in our soil

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 formed 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.

Humus is formed from dead organic matter over long periods of time

How does humus affect plants?

Humus in the soil is a true 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 make up for missed fertilizers.

A humus-rich soil offers less resistance to the roots, so they can penetrate more easily

Together with clay, which is also found in many soils, humus forms stable, three-dimensional compounds that prevent your soil from compacting too quickly when walked or driven over. That toonaturally benefits your plants, which often do not like it 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, allowing plants to germinate earlier and start growing faster.

Last but not least, a sufficient humus content is essential for he althy 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.

Billions of small and tiny creatures live in he althy soil. Soil bacteria can be visualized by culture on nutrient media

Humus formation: 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 fully research the underlying process. 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 soil: earthworms, bacteria, fungi, the smallest insects and sometimes even supposed pests such as moles or voles.

In natural habitats, moles and voles mix the soil and thus promote humus formation

They carry out the first step in humus formation: They crush, eat, digest and transport the dead material 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 are broken down more slowly than others: sugars or starches, which can also be found in leaf litter or root remains, are easily broken down and are broken down more quickly than proteins, for example. 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 twigscan be found that contain a lot of lignin.

The easily decomposable components are broken down first, while the stable, lignin-containing leaf veins last longer

During decomposition, 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 calcium ions or other soil minerals, the large, visible humus flakes that can be found on a compost heap are formed.

Humin substances are very difficult to break down again. However, a fundamental change in the environmental conditions can also be made possible.

The formation of large crumbs, flakes or "aggregates" occurs through the cementing of the already large humus molecules with calcium ions and other soil minerals

Humus formation and mineralization

When the organic matter in the soil becomes humus, it is called "humification". But all that dead material can also be used in another way, namely by "mineralizing" it.

To put it simply, the term “mineralized” means that all of these leaves, bits of root and dead soil animals are broken down into their atomic or molecular components. 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 by other living beings againbe used.

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 into the air as CO2, minerals go into the soil solution.

Bacteria living in the soil break down the organic material into its components. For example, these Nitrosomonas are part of the conversion of ammonium to nitrate

This type of "recycling" always occurs in cycles in nature and of course saves every hobby gardener a lot of fertilizer, because the minerals released can serve as nutrients for the plants. Of course, no useful humus is formed during the mineralization of organic material, and the humus itself can also be broken down by mineralization.

There are two possibilities for the undecomposed organic matter in the soil: full mineralization or partial decomposition followed by 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 should not want one or the other alone for our soil, our goal is - with sufficient humus content - a balanced ratio. The influencing of this ratio is called "humus economy".

It is possible to influence the relationship between humification and mineralization through 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. For more detailed information and practical application tips on humus management, read on here.

Because it is the basis of food for our plants, more attention should be paid to the soil

Buy hummus: you need to pay attention to this

The formation of humus is a lengthy, natural process that requires a lot of patience. If you want to go a little faster, you can sort of buy hummus and distribute it where you need it. This is how you can buy hummus:

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

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 summarized all detailed information on buying hummus for you in our special article.

If you want to keep the hummus you just bought, you must protect it from degradation and encourage the build-up of new humus. You can use the tips from the article on humus management for this.

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