Humus - as every amateur gardener knows - is something extremely valuable for the garden. What it is exactly, however, cannot really be answered by many a knowledgeable plant expert. In the following, we will take a close look at what humus is made of, how it is formed and what it can do in the garden.

Humus is basically rotted organic material

Table of Contents

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  1. the essentials in brief
  2. Definition humus
  3. How is humus formed?
  4. What is hummus made of?
  5. Meaning of humus
  6. use of hummus
  7. When to promote hummus?
  8. frequently asked Questions

    9. the essentials in brief

    • Humus is decomposed organic matter
    • The humus content in the soil varies from 1 to 15%
    • Humus is very nutritious and contains, among other things, phosphorus, nitrogen and sulphur

    What exactly is hummus?

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

    However, when considering the decomposition process of organic matter, it starts to get complicated. Because the boundary between decomposed and undecomposed material is floating. And this is mainly because the decomposition process goes through several stages and the exact "time of death" of the material cannot be precisely determined.

    Two different types of humus are produced during decomposition - nutrient and permanent humus. These types of humus differ in their persistence, which is determined by the degradability of their components. Nutrient humus consists of half rapidly degradable carbohydrates and the other half lignin. Permanent humus, on the other hand - which basically only represents a later stage of decomposition - can survive for thousands of years as a stable organic substance.

    digression

    proportion of humus in the soil

    The humus percentage 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 peat soil (defined as soil with at least 30 centimeters of peat) where the humus content can be around 80%. Most of the humus is in the topsoil.

    Here is an overview of the humus content in the soil in Germany to illustrate the real average values. It comes from the result of an investigation by the Federal Institute for Geosciences and Natural Resources as part of the project "Contents of organic matter in Germany's topsoil". Around 9,000 soil profile data from the three most common types of land use in Germany - arable farming, 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 formed?

    So humus is formed from organic material in the soil - 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 legacies from animals, such as skin coverings, bristles or excrements, are part of it.

    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 each other, for example in the form of oxidation or hydrolysis. The cell structure remains intact, which means that the outer form remains.

    2. Initial phase

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

    3. Crushing phase

    Worms and other insects break down the organic material

    In the shredding phase, the material is - no 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 by enzymes. Finally, inorganic substances such as water or nitrogen dioxide are also formed. This process ultimately produces mineral and poorly degradable material such as lignin, which is primarily broken down and converted by fungi. This so-called mineralization (i.e. quasi terrestrial) 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 crumbling of the humus, which ensures its soil-structuring and water- and nutrient-retaining properties.

    What is hummus made of?

    That cannot be answered in general. Because the composition of the organic material that decomposes into 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 primarily measured by its nitrogen-carbon ratio. Nitrogen is the valuable growth-promoting component. In addition, humus also contains phosphorus and sulfur, which are also important substances that promote plant growth.

    Meaning of humus

    Hummus contains many valuable nutrients

    Above all, humus has a water balance-regulating, structure-forming and fertility-promoting importance for the soil. Above all, the substances it contains, nitrogen, sulfur and phosphorus, are essential for plant growth. In addition, the crumbly consistency of the humus acts like a spongy structure, which effectively helps the soil to cope with water shortages and excesses. As a result, the soil water is available to the flora and fauna for longer and flooding can be effectively intercepted.

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

    In addition, humus can bind CO2 - 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 drying out and to protect the soil. This means above all that important soil organisms, especially the microfauna, feel particularly comfortable under a protective layer of mulch and diligently promote the accumulation of humus.

    When promoting humus in your garden soil, you should consider the following:

    • apply compost or mulch (€239.00) before winter to protect against the cold and first remove the layer in spring to allow sun and heat 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 by chemical pollutants, resins, fungi and weed seeds. If you make compost and thus your humus yourself and garden consistently without using chemical pesticides, you will get the best "organic hummus".
    • an additional inoculation with nitrogenous plant manure (especially from stinging nettles) in the spring makes mulch application even more effective. Above all, it gives plants an initial growth spurt when they are sown
    • Apply a layer of mulch thick enough to prevent weeds from invading the area.

    Mulch protects against weeds and dehydration

    Apart from nutrient and permanent humus, there are many other distinctions within the humus cosmos. A distinction is made above all between the composition of the starting materials and the resulting effects. Different plants and animal remains contain different substances that affect the soil accordingly.

    If you want to make humus yourself, the best way to do this is through gardening composting and incorporating the compost soil into the soil, where humus can then develop with the help of local soil fauna and minerals. Even simple mulching creates a nourishing layer of humus on the topsoil. Depending on the starting materials from which the compost is composed, a different type of humus is formed. Leaves are one of the most important mulch materials, because they also contribute significantly to the formation of humus 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 wood cuttings: for mulching under acid-loving plants such as rhododendrons or berry bushes
    • Walnut, sycamore or chestnut leaves: contain a lot of tannin and are difficult to decompose, therefore unsuitable for mulching or humus production

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

    tips

    If you want to mulch to build up humus, it is worth shredding the mulch material well before spreading - for example with a shredder or for the lawn directly with a mulching lawnmower. In this way you promote the stages of decomposition and the work of microorganisms and enzymes. Your garden soil will benefit more quickly from the nourishing, structure-providing and water balance-regulating effect of the resulting humus.

    When does humus promotion make sense?

    It always makes sense to promote the humus content in the garden soil. Above all, of course, if you are cultivating a vegetable garden from which a large harvest is to fall. It is not for nothing that the compost that you produce and spread to promote the humification of your garden soil is also referred to as the "gardener's black gold". In general, a humus content of less than 4% is considered low - much overturned and leached arable land soils are usually far lower. Your garden soil should preferably have a humus content of over 4%, depending on how high or low its density is.

    If you're not sure how much your garden soil needs a constant fertility boost, you can specifically test your soil for its humus content. However, this requires a certain amount of equipment, as shown in the following video:

    youtube

    frequently asked Questions

    What is the difference between humus and compost?

    The differentiation actually lies only in the impetus for its creation: in the case of humus it is initiated by nature, in the case of compost by man. Man places his compost heap separately from the natural soil (e.g. in a compost shed or on a simple accumulation) specifically to improve his garden soil and counts on the help of microorganisms. Humus, on the other hand, is a pure product of nature and naturally forms compounds with minerals and local microorganisms. When compost is incorporated into the garden soil, it gradually turns into real humus.

    How to make humus yourself

    Basically, this has already been answered with the previous question: Proper humus is only created through natural decomposition by local minerals and microorganisms in the soil. You can only "make" humus yourself by giving the natural soil the task to do so. If you already have compost that has already decomposed 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 larger 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 remains in the natural soil for a long time and continues to decompose locally. You can usually pick up compost in humus and soil works for prices between 5 and 10 euros per cubic meter (not by weight). For an individual delivery, a decent transport fee is often due.

    Where is humus soil cheap?

    Large hardware stores such as Obi or Hornbach offer compost soil with a humus content at very reasonable prices. But don't let the low price tempt you. Because and often the offers are 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 come from incorrectly stocked organic bins. You can get your humus completely free of charge and with careful garden waste management also free of pollutants by composting yourself - the price here is just patience.

    How do you recognize good hummus?

    To distinguish good hummus from less good hummus, you can simply do sensory tests. Trust your nose, your hands and your eyes. Valuable humus feels balanced, crumbly and evenly moist, smells pleasantly woody and mushroomy and has a clear, dark colour. Plastic-packaged, cheap "industrial" humus from hardware stores often has a high water and even too high a nutrient content. Of course, more money can be made with the high water content, especially since the compost packs are sold by weight.

    Is hummus suitable for cultivation?

    Definitely. Humus is an important component of potting 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 growing soil yourself by mixing well-ripened compost, i.e. humus in the preliminary stage, with sand.

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