The secrets of humus

the essentials in brief

• Humus is decomposed organic material
• The humus content in the earth varies from 1 to 15%
• Humust is very rich in nutrients and contains, among other things, phosphorus, nitrogen and sulfur

What exactly is humus?

At first glance, defining humus is not difficult: it actually only describes the decomposed portion of organic material in the earth, or the part that is in the process of decomposition. Its counterpart or its preliminary stage is the detritus - the undecomposed part. Living organisms make up the rest of the mineral earth - biomass.

also read

• What is the difference between humus and compost?
• Everything you need to know about humus soil
• Mix the potting soil yourself

When looking at the decomposition process of organic material, however, it starts to get complicated. Because the boundary between decomposed and undecomposed material is floating. And that's mainly because the decomposition process goes through several stages and the exact “time of death” of the material cannot be precisely determined.

The decomposition process produces two different types of humus - nutrient and permanent humus. These types of humus differ in their persistence, which is determined by the degradability of their components. Nutritional humus consists of half of rapidly degradable carbohydrates and the other half of lignin. On the other hand, permanent humus - which basically only represents a later stage of decomposition - can last for thousands of years as a stable organic substance.

Digression

Humus content in the soil

The humus content is usually in a fairly low range. An average Central European soil (i.e. silty to sandy or clayey loam soil) only contains between 1 and 15% of it. An exception is bog soils (defined as soil with at least 30 centimeters of peat covering), where the humus content can be around 80%. Most of the humus is in the soil.

Here is an overview of the humus content in the soils of Germany to illustrate the real average values. It comes from the result of a study by the Federal Institute for Geosciences and Raw Materials as part of the project “Contents of organic matter in topsoil Germany”. Around 9,000 soil profile data from the three most common types of land use in Germany - arable, forestry, forestry and grassland - were evaluated from 1985 to 2005.

	Farmland	Forestry / forestry	Grassland
Humus content	1 to 4 %	2 to 8%	4 to 15%

How is humus made?

So humus is created from organic material in the earth - what is that exactly? First and foremost, of course, plants and parts of plants that are no longer alive such as dead wood, fallen leaves or root remains. But also the legacies of animals, such as molting coats, bristles or excretions, are included.

During decomposition, the organic material goes through several stages in which various biochemical reactions and mechanical processes take place. These stages are as follows:

1. Preliminary phase

In the preliminary phase of decomposition, only the organism's own substances react with one another, for example in the form of oxidation or hydrolysis. The cell structure remains intact, which means that the external shape is retained.

2. Initial phase

In the initial phase, in addition to further biochemical reactions, there are also mechanical washouts, e.g. of amino and other acids. The substances released in the process attract a large number of microorganisms that feed on them.

3. Shredding phase

In the shredding phase, the material is - who's any wonder - significantly shredded. Namely from the so-called macrofauna, i.e. worms, spiders, insects and snails. They eat parts of the material, excrete it in a different way and work it into the soil.

4. Dismantling and conversion phase

Finally, the fragments are split up by enzymes. In the end, inorganic substances such as water or nitrogen dioxide are also formed. In the end, this process creates mineral and difficult to break down material such as lignin, which is mainly broken down and converted by fungi. This so-called mineralization (quasi soil formation) is also referred to as the clay-humus complex, i.e. the combination of organic and inorganic fragments. Above all, humic substances form a connection with clay minerals and ensure the valuable crumb formation of the humus, which ensures its soil structuring and water and nutrient-retaining properties.

What is humus made of?

There is no general answer to this. Because the composition of the organic material that decomposes to form humus is always different - depending on the plant and animal species whose legacies come together locally. (and also their age!)

The type of humus is measured primarily on the basis of its nitrogen-carbon ratio. Nitrogen is the valuable component that promotes growth. In addition, humus also contains phosphorus and sulfur, also important substances that promote plant growth.

Meaning of humus

Above all, humus has a water balance-regulating, structure-building and fertility-promoting role for the soil. In particular, the substances nitrogen, sulfur and phosphorus it contains are essential for plant growth. In addition, the crumbly consistency of the humus acts like a sponge-like structure, which effectively helps the soil to deal with water shortages and excesses. This means that the soil water is available to the flora and fauna for longer and floods can be intercepted well.

Its porous structure also makes the humus an effective filter for pollutants such as residues from pesticides.

In addition, humus can bind CO2 - and that for thousands of years.

What is humus used for?

Humus is generally used to enrich the garden soil with nutrients, to store water or prevent dehydration and to protect the soil. This primarily means that important soil organisms, especially the microfauna, feel particularly comfortable under a protective layer of mulch and diligently promote humus enrichment.

You should consider the following when promoting humus in your garden soil:

• apply compost or mulch (€ 99.99 at Amazon *) before winter to protect against the cold and remove the layer in spring first to allow sun and warmth to reach the ground
• Especially dark compost material is conducive to the spring warming of the soil
• it is better to use your own compost for humus enrichment, the raw materials of which you can control. Humus soil from composting plants or conventional agriculture is more frequently contaminated with chemical pollutants, resins, fungi and weed seeds. If you make compost and thus your own humus and garden consistently without the use of chemical pesticides, you will get the best “organic humus”.
• An additional inoculation with nitrogen-containing plant manure (especially from nettles) in spring makes mulch application even more effective. Above all, it gives plants an initial growth spurt when sown
• Apply a layer of mulch thick enough so that weeds have no chance of conquering the area.

Apart from nutrient and permanent humus, there are many other distinctions within the humus cosmos. A distinction is made between the composition of the starting materials and the resulting effects. Different plants and animal legacies contain different substances that have a corresponding effect on the soil.

If you want to make humus yourself, the best way to do this is through the usual horticultural composting and incorporation of the compost soil into the soil, where humus can then be created with the help of the local soil fauna and minerals. A nourishing humus layer is also created on the top of the soil simply by mulching. Depending on which raw materials the compost is made of, a different humus is created. Foliage is one of the most important, because mulch materials also contribute to humus formation in nature. Basically the following can be stated in this regard:

• Fruit tree or beech leaves plus lawn clippings and other nitrogenous material (e.g. manure): for plants that need nutrients, especially vegetables
• Oak leaves together with bark and woodcut: for mulching under acid-loving plants such as rhododendrons or berry bushes
• Walnut, plane tree or chestnut leaves: very tannic and difficult to rot, therefore unsuitable for mulching or humus production

For the lawn, mulching with your own lawn is a well-suited means of creating natural humus directly on the spot. Studies have shown that lawns that are regularly cut with a mulcher lawnmower develop a more robust sward and are more resistant to competing plants and grass diseases.

Tips

If you want to mulch in order to build up humus, it is worthwhile to shred the mulch material well before spreading - for example with a chopper or for the lawn directly with a mulcher lawnmower. In this way you promote the decomposition stages and the work of microorganisms and enzymes. In this way, your garden soil benefits faster from the nourishing, structure-providing and water balance-regulating effect of the humus that is created.

When does humus promotion make sense?

Basically, it always makes sense to promote the humus content in the garden soil. Especially, of course, if you are cultivating a kitchen garden from which you want a lot of harvest to fall. It is not for nothing that the compost, through the production and application of which you promote the humification of your garden soil, is also known as the “gardener's black gold”. In general, a humus content of less than 4% is considered to be low - a lot of revolved and depleted arable land is usually far below that. Your garden soil should, depending on how high or low its density, have a humus content of over 4%.

If you are not sure how much your garden soil needs a permanent fertility sprayer, you can do a very specific test of your soil for its humus content. However, this requires certain equipment, as shown in the following video:

Youtube

frequently asked Questions

What is the difference between humus and compost?

The differentiation is actually only in the origin: with humus it is initiated by nature, with compost by humans. Humans create their compost heap separately from the natural soil (e.g. in a compost shed or on a simple pile) specifically to improve their garden soil and count on the help of microorganisms. The humus, on the other hand, is a pure work of nature and naturally forms compounds with minerals and the locally occurring microorganisms. When compost is incorporated into the garden soil, it gradually turns into real humus.

How can you make humus yourself?

Basically, this has already been answered with the previous question: real humus is only created through natural decomposition by local minerals and microorganisms in the earth. You can only “make your own” humus by giving the natural soil the task. If you already have advanced compost available during decomposition and work it into the soil, you will get real humus where you want it: in the vegetable and flower beds or in the lawn.

Where do you get humus garden soil in large quantities?

You can produce large amounts of compost for the garden in waste management companies or separate humus and soil plants. As a rule, the valuable, nutrient-rich and structure-forming soil is sold as compost soil and not as humus soil, because, strictly speaking, one can only speak of humus if it has remained in the natural soil for a longer period and decomposes further locally. You can collect compost soil in humus and earth works for prices between 5 and 10 euros per cubic meter (not by weight). A proper transport fee is often due for an individual delivery.

Where can you find humus soil cheaply?

Large hardware stores such as Obi or Hornbach offer compost soil with humus content very cheaply. But don't let the low price seduce you. Because and often the offers are about industrial humus from composting plants, which is not insignificantly contaminated with residues of chemical pesticides, weed seeds, fungal spores and even plastic and small amounts of heavy metals that comes from incorrectly stocked bio bins. Completely free of charge and, with careful gardening waste management, also pollutant-free, you can compost your humus yourself - the price here is just patience.

How do you recognize good humus?

To distinguish good humus from less good humus, you can simply do sensory tests. Rely on your nose, hands and eyes. Valuable humus feels balanced, crumbly and evenly moist, smells pleasantly woody and mushroom and has a clear, dark color. Inexpensive "industrial" humus packaged in plastic from hardware stores is often high in water and even too high in nutrients. You can of course earn more money with the high water content, especially since the compost packs are sold by weight.

Is humus suitable for cultivation?

In any case. Humus is an important part of cultivation soil because it has a wonderfully crumbly, airy structure and can store a lot of water, which is ideal for the development of young roots. You can easily make cultivation soil yourself by mixing well-matured compost, so to speak humus, with sand in the preliminary stage.