## 4 Discussion
[39] also reported that a change in the soil microclimate caused by different residues of the leguminous cover crops influenced the metabolism of microorganisms, thus significantly contributing to the catabolic activity of soil dehydrogenase. According to [PERSON] et al. [40], the much of stubble catch crops retains significant amounts of rainwater, and the soil moisture level affects the activity of this enzyme. The activity of catalase, which is also an oxidoreductase, was similar to the dehydrogenase activity. The activity of this enzyme can also be used for the monitoring of soil quality. Catalase can be found in the cells of all soil microorganisms that use oxygen for respiration (aerobes, facultative anaerbes). [PERSON] et al. [41] found a significant relationship between catalase activity and the oxygenation of soil modified by compaction and moisture. In our experiment, the activity of this enzyme increased after the application of the undersown cover crop of red clover, and, above all, after the application of the bacterial consortium. During the growing season of spring barley, the stressful abiotic factors (low rainfall) were mitigated by biof sterilization with PGPR and by the application of the bacteria in combination with the undersown cover crops. Acid phosphatase is another important enzyme indicating soil quality and the availability of phosphorus. When the availability of soil phosphorus is low, the exudation of acid phosphatase (PAC) increases. However, this enzyme is exuded not only by communities of soil microorganisms but also by the plant itself. In consequence, the amount of acid phosphatase in the pedon increases significantly, which is often negatively correlated with the count of microorganisms. In our study, the soil samples collected from the organic spring barley plantation were characterized by lower acid phosphatase activity in the variants where only PGPR as well as PGPR together with undersown ryegrass as a catch crop had been applied. This means that the active biological factor increased the content of assimilable phosphorus in the soil. Such dependencies were presented in the studies conducted by [PERSON] [11; 42] and [PERSON] [43]. In another study, [PERSON] and [PERSON] [44] also observed the higher catabolic activity of this enzyme in an experimental treatment without phosphorus fertilization. As results from research on some PGPR of the _Bacillus_, _Enterobacter_, and _Pseudomonas_ genera show, these microorganisms stimulate plant growth by dissolving soil phosphates. This effect is regulated by two main mechanisms: the lowering of soil pH through the production of organic acids and the mineralization of organic phosphate by acid phosphatases and phytases [45]. The results from the observations made in our study show that the biological parameters of the soil under the organic spring barley plantation were stimulated by the PGPR consortium. These bacteria can affect plants both directly and indirectly. Their direct effect consists in making phosphorus and potassium available to plants and in the production of phytohormones. The indirect effect of the PGPR consists in the production of siderophores and hydrolytic enzymes and the protection and promotion of the growth of crops [46; 47; 48]. The PGPR also stimulate the indigenous soil microbiome.