Soil Management

Soil microorganisms

Soil microorganisms include bacteria, archaeons, viruses, some fungi, algae and protozoa. In the soil environment, the importance of microorganisms manifests itself, among other things, in the formation of soil crumbling structures and in the mineralisation of organic matter, providing plants with easily-assimilable nutrients. Soil microorganisms are responsible for processing soil substances and cycling elements that are important for many processes in the soil environment. In the vicinity of the roots of plants, i.e. in the so-called rhizosphere, micro-organisms are very active and play an important role in shaping the conditions for plant development.

They not only facilitate the uptake of mineral nutrients by plants, but also protect them from pathogens. Microorganisms are able to ‘recognise’ their plant hosts, so each plant species has a different set of microorganisms populating its root tissues. For this reason, simplified rotations, or lack thereof, significantly deplete the diversity of microorganisms in the soil.

The dead soil organisms are decomposed by micro-organisms and the decomposition products are the building blocks for soil humus, which influences the basic chemical and physical properties of the soil. Soil humus is responsible for maintaining the correct soil structure, its water retention capacity and also influences the soil’s resistance to wind or water erosion. The humus content of mineral soils is one of the main indicators of their fertility.

A very valuable element of the soil ecosystem is the presence of bacteria that supply nitrogen to plants. Some of the bacteria can fix nitrogen from the air by living alone in the soil, but this requires the correct pH and the presence of food – e.g. post-harvest residues. Bacteria living in symbiosis with faba bean plants (e.g. peas, broad beans, clover, alfalfa, lupins or serradella) fix much larger amounts of atmospheric nitrogen. The post-harvest residues of the faba bean plants are not only a valuable source of nitrogen for the succeeding crops grown in the crop rotation, but also an extremely important factor positively influencing the structure and other fertility parameters of the soil.

The microbial activity of soils is an important indicator of the fertility and fertility of the soil ecosystem, and also provides valuable information on the changes occurring in the environment as a result of the interactions of both independent and human-dependent factors. The micro-organisms present in the soil secrete a number of important enzymes into the soil that are responsible for the proper functioning of the soil ecosystem. They are mainly responsible for the breakdown of organic matter and the formation of soil humus. In addition, they enable plants to draw on the mineral substances available in the soil (they are involved in the transformation of nitrogen, phosphorus, sulphur and other elements found in the environment), participate in the detoxification processes of pollutants (e.g. decomposition of plant protection products) and nitrification and denitrification, and are involved in the degradation of lignins, cellulose and other plant cell components. The micro-organisms produce chelating compounds that promote the uptake of micronutrients by plants. The abundance of soil microorganisms, as well as the activity of soils, depends on a number of factors, such as soil pH, soil moisture and soil organic matter content. The development and activity of microorganisms depends on many environmental factors, such as pH, organic matter content and individual elements, especially humidity and temperature, but also on the way the plants are cultivated and protected.

Among the soil micro-organisms, there are also those that – from our point of view – have a negative effect, causing plant diseases, for example.

The largest contribution to the soil ecosystem belongs to saprotrophs represented by bacteria, or fungi, which use a mechanism called antagonistic interaction (e.g. competition, parasitism, predation) towards pathogens, relying on interspecific relationships among the populations present, leading to adverse effects for one or both parties. In addition, the soil environment activates mechanisms that help micro-organisms to survive the harsh conditions of the environment in which they live. Such phenomena include a condition known as anabiosis (a state of reduced activity of an organism), hyperparasitism (a condition in which a host of a parasite becomes another parasite, to the benefit of the main host), or the more familiar mycorrhiza (symbiosis of many fungi with the roots of plants, including cultivated plants). In practice, it boils down to maintaining an equilibrium that protects against excessive pathogen growth.

When the soil environment cannot cope with pathogen accumulation, human action is required. Protection against pathogens can be carried out both through biological protection (e.g.: plant inoculation, use of biological plant protection preparations), mechanical protection (soil improvement treatments), agronomic protection (sowing dates, plant succession) and through chemical treatments in the form of suitable plant and soil protection products. Biological protection most commonly uses antagonistic organisms, as well as the above-mentioned phenomenon of over-parasitism. In addition, inoculations play a major role in increasing the activity of microorganisms in the soil – for example, inoculations for faba bean plants can significantly increase the fixation of atmospheric nitrogen, resulting in a better yield for these plants. Proper soil pH regulation also plays a huge role.