Biological life of the soil

Soil organisms that support the farmer

Macroorganisms

The best-known soil macroorganisms are earthworms. They are true engineers of the soil ecosystem. By burrowing through the soil, they create a network of drainage and aeration channels — loosening and aerating the soil, improving its structure, and facilitating water infiltration. By ingesting soil together with organic residues, earthworms mix organic and mineral matter and excrete so-called coprolites — humus-rich granules that form ready-made soil aggregates with high fertility. It is estimated that in arable soils, earthworms can process and mix the plough layer within a few years, effectively acting as a natural plough.

How does biodiversity affect the soil?

All these organisms transform soil into a living micro-world. The effects of their activity translate directly into soil fertility. Thanks to them:
- Nutrients are continuously released from dead organic matter (soil works like a living compost system 24/7),
- A soil structure favorable for plants is formed,
- Biodiversity also means greater resistance to diseases. Many beneficial bacteria and fungi act antagonistically toward plant pathogens — for example by competing for nutrients or releasing natural antibiotics in the root zone. A living soil can therefore protect crops much like an immune system.

Important! Healthy soil contains an entire army of microorganisms working for the farmer 24 hours a day — for free, as long as they are provided with the right conditions.

How to create favorable living conditions in soil?

Unfortunately, the intensification of agriculture over recent decades has often disrupted this delicate ecosystem. Overuse of chemicals and heavy machinery has reduced the biological richness of soils, making them less alive. So how can a farmer support biological soil life and provide optimal conditions for its development?

Moisture

Soil organisms are most active in a moist environment. When soil dries out, many bacteria enter a dormant (inactive) state, and earthworms retreat deeper or die. In practice, maintaining moisture means avoiding long periods when the field is completely bare (without plants protecting it from drying out) and taking care of soil structure and humus, which retain water.
- Plant cover (e.g. cover crops, stubble, mulching, mulch) acts as a shield against evaporation — it limits surface heating and helps retain moisture.
- Humus, in turn, absorbs water like a sponge (more in Chapter 2), maintaining a favorable microclimate for microorganisms.

On farms located in drier areas, it is worth considering conservation tillage, such as:
- Loosening without soil inversion, e.g. subsoiling, as well as operations that do not disturb soil horizons, such as shallow discing or using a cultivator with spring tines instead of ploughing,
- Leaving residues on the surface to reduce water evaporation from soil.

A good practice is also irrigation during prolonged droughts — for example by sprinkler irrigation or by applying slurry at the right moment — to prevent complete drying of the soil profile. At the same time, excess water must also be avoided. Beneficial soil fauna are mostly aerobic organisms, and too much water displaces air from soil pores, leading to anaerobic conditions in which organisms die or become inactive (while undesirable rotting and reduction processes intensify). That is why on waterlogged soils or after heavy rainfall, drainage (melioration, drainage systems) is important to restore oxygen balance.

Important! The golden rule is to keep soil neither too dry nor too wet — the goal is to maintain proper proportions of water and air in soil, ensuring moderate moisture with access of oxygen to the root zone. In practice, this is achieved through plant cover, humus, and, if necessary, drainage.

Access to organic matter

Soil organisms feed on organic matter — when it is lacking, they starve and their populations decline. Therefore, the more organic residues we supply to soil, the more vigorous biological life becomes.

It is also worth ensuring a diverse “menu,” as each type of organic matter feeds slightly different groups: sugars and proteins from young plants are quickly consumed by bacteria; lignin and cellulose from straw are decomposed more slowly by fungi and actinomycetes; manure supplies a whole spectrum of compounds, both easily and more difficult to decompose. Microbes can also be fed through proper crop rotation — by sowing plants that leave large amounts of root residues (e.g. deep-rooting lupins, clovers) or by using cover crops (green manure) that provide fresh biomass for processing (more in Chapter 4). Leaving stubble with crop residues over winter also supplies food for earthworms and saprophytic fungi during colder seasons.

Important! Monoculture and lack of organic fertilizers drastically reduce the food base — as a result, soil becomes biologically depleted.

Minimal interference

Most organisms need “peace and quiet” to function properly — a stable, undisturbed environment. The same applies to soil organisms. Excessive human interference — mainly intensive ploughing, frequent mixing of soil with heavy machinery, and overuse of chemicals — has a destructive effect on soil life. Sometimes it literally turns their micro-world upside down. This issue is developed further in the next subsection.

Impact of tillage practices on soil life

he most negative effects on soil organisms come from intensive mechanical operations (especially ploughing) and a one-sided, chemical approach to crop production.
Important! High tillage intensity and excessive use of mineral fertilizers and plant protection products lead to the disappearance of fertile soils.

Mechanical soil disturbance

The more frequently and deeply soil is disturbed, the harder it is to maintain a stable population of beneficial microbes. For them, driving heavy machinery into the field is like a gigantic bulldozer physically destroying their habitats.
- Ploughing tears fungal mycelia apart, cuts earthworms or throws them onto the surface to be eaten by birds, and destroys soil aggregates on which bacterial colonies are established.
- After soil inversion, microorganisms adapted to surface layers are buried at the bottom of the furrow, where they lack oxygen and food — and die. At the same time, organisms from deeper layers are brought to the surface, exposed to sunlight and fluctuations in temperature and moisture — and they also die.
- In addition, heavy machinery compacts soil, closing pores and cutting off the oxygen supply needed by microorganisms.

You can read more about how reducing ploughing affects field condition in e-book 3.

Thoughtless use of chemical agents

Unconsidered use of chemicals (especially pesticides) can also harm microorganisms. For example:
- Frequent application of soil fungicides or seed treatments reduces not only pathogenic fungi but also beneficial ones (e.g. mycorrhizal fungi),
- Strongly acidic nitrogen fertilizers locally acidify soil, changing microflora composition (at low pH, beneficial bacteria decline while acid-tolerant fungi increase),
- Excess readily available nitrogen from mineral fertilizers may cause symbiotic microorganisms (e.g. nitrogen-fixing bacteria) to become “lazy” — plants do not enter symbiosis with them, and the bacteria die without a host,
- Herbicides and insecticides can reduce populations of beneficial nematodes, predatory insect larvae, and other organisms that are part of the food chain.

Important! Some tillage operations are, of course, necessary — the key is shifting from an intensive approach to an intelligent one. Instead of ploughing to the same 30 cm every year, soil can be loosened with a subsoiler every few years, while daily practice is limited to shallow operations. In this way, deeper layers remain untouched as a reservoir of life and structure, while the seedbed is prepared only at the surface level.