## 4 Discussion
BCAs and MSADs containing populations of useful microorganisms, when introduced into the soil, increase microbial populations, biodiversity, and biological activity, which have a positive effect on plant health and potato yield [56; 57; 88]. This study has shown that all preparations (EM, UG, BR) classified as MSADs protect potato tubers against silver scurf to a much lesser extent compared to BCAs, and the level of their effectiveness is comparable and non-diversified significantly--between 20.9% and 26.2% (Figure 4). It has been demonstrated that EM, as much as BCAPo, suppresses the development of _S. cables_, whereas the efficacy of UG and BR is significantly lower, i.e., 20.0% and 14.0%, respectively. The treatment of seed potatoes and the introduction of BR preparation to the soil reduces black scurf severity by 45.5%, which is the same as BCAs. In contrast, the suppression of _R. solani_ by EM is significantly weaker (E = 38.3%). The mechanism of the impact of microorganisms introduced into the soil and applied onto the surface of seed potatoes is complex and multifaceted. It should be kept in mind that even a slight decrease in soil microbial diversity or changes in soil structure and functions may affect the availability and uptake of nutrients as well as plant health [99; 101]. On the one hand, we have their proven protection against pathogens, and on the other hand, their yield-forming effect. This study shows that the diverse consortia of microorganisms included in MSADs cause higher increases in potato yields than the individual species of BCAs microorganisms. EM contributed to increases in the tuber yield by 16.4%, the Biogen Rewital (BR) preparation by 13.0%, and UGmax (UG) soil conditioner by 9.9% (Figure 5). In a multi-year study, [PERSON] and [PERSON] [102] showed that EM increases the number of and the coefficient of reproduction of seed potatoes. In addition, the authors indicate that EMFarmaTM and Ema5 TM preparations increase dry matter and starch content, decrease the content of reducing sugars and sucrose, and also have a positive impact on other qualities impacting the quality of processed potato products [56; 57]. The increase in yields, starch, and vitamin C content in the Tajfun cultivar was observed due to the use of the soil conditioner UGmax [103]. This preparation, used at different doses and times, limited the percentage of tubers with common scalp symptoms and decreased its intensity [32]. Insufficient scientific reports on the impact of MSADs on potato yields and health show that there is a need to fill this gap in research. In changing economic and climate conditions, when the growing global area of cultivation is suffering from drought, and there is a need to give up or reduce the use of chemicals to a minimum, MSADs preparations alongside BCAs may prove to be a very important part of cultivation technology of potato and other plant species. PGP also plays an important role in modern plant production technologies. The conducted experiment is indisputable proof that the Kelpak SL (PGPE_m_) biostimulant, containing auxins and cytokins derived from the _Eckonia maxima_ algae, is most favorable for potato yields. Yieldincreases were, on average, 17.4%, which means that on average, a 7.0 t larger yield can be obtained per 1 hectare. According to [PERSON] [104], Kelpak SL was applied onto leaves three times during the growing season, which increased the cultivar Tajfun's potato yield by 0.9 t-ha\({}^{-1}\). Other studies show that, on average, 21.6% potato tuber yield increases were obtained after two sprayings with this biostimulant [105]. Cytokines have an impact on the enhancement and growth of the plant root system [106; 107]. Therefore, the results obtained are not surprising; they only confirm the yield-enhancing role of PGPE_m_[108; 109; 110]. The conducted research study has shown that PGPE_m_ protects potato tubers against silver scurf better than MSADs (Figure 4). However, its effectiveness against _R. solani_ (E = 36.1%) and _S. scabies_ (E = 31.3%) is the same as that of EM.