## 3 Results
### Thermodynamic Background for Control of Rhizoctonia solani AG 2-2 IIIB
solani_ AG 2-2 IIIB belongs to obligate aerobic microorganisms with optimal pH values varied between 4.0 and 8.0. The considerations of its metabolism in relation to aerobic conditions, expressed in the pH-Eh dependence, are as follows. The aerobic zone is in the pH range from 0.0 to 13.0 and covers the area of 600 mV in the range of E\({}_{0}\)\({}^{\prime}\) from +200 mV (point No. 12) to +814 mV (point No. 15). However, taking into account the fact that air content is not 100% O\({}_{2}\) (i.e., is not 1 M) but only 21%, the value of the standard redox potential (E\({}_{0}\)\({}^{\prime}\)) will not be equal +814 mV, but only +500 mV. Thus, aerobic conditions in the expression of redox potential, are in the range of E\({}_{0}\)\({}^{\prime}\) from +200 to +500 mV (points No. 12 and No. 11, respectively). Considering that _R. solani_ AG 2-2 IIIB has pH limitations, a suitable zone for its growth is limited by the points No. 5, 6, 9, 10. In other words, _R. solani_ AG 2-2 IIIB can grow only under aerobic conditions in the pH range varied between 4.0 and 8.0 and in the Eh range from +200 to +500 mV. Its existence outside of this specified zone is impossible. However, it should be taken into account that Rhizoctonia must be suppressed in soil ecosystems. Therefore, it is obvious that strong acidic, strong alkaline, and high potential conditions are not suitable, because they will lead to drastic changes in the soil microbiome. Consequently, we chose suppressive extreme factors that provide slightly alkaline, anoxygenic (absence of O\({}_{2}\)), and anaerobic (absence of O\({}_{2}\) and Eh \(\leq-200\) mV) conditions. Such suppressive factors belong to physicochemical or biological categories. Physicochemical suppressive conditions can be created as follows. Slightly alkaline conditions can be created by phosphate buffers (mixture of Na\({}_{2}\)HPO\({}_{4}\) and Na\({}_{3}\)PO\({}_{4}\)) and anoxygenic ones--due to the replacement of air with argon and anaerobic conditions--by the application of argon and low-potential reducing agents, such as Fe(II) citrate or Ti(III) citrate). Biological systems can simultaneously generate all three mentioned suppressive factors. The soil or compost microbiome is a good example. The natural microbiome is diversified and consists of aerobic, facultative, and obligate anaerobic microorganisms capable of fermenting a wide range of organic substrates. To see the effect, there is no need to identify the species content in microbial community. The conditions of the microbial community's growth are of most interest. Clearly, when soil is flooded (a high layer of water) and some organic substrates (carbohydrates, proteins, etc.) are introduced into the soil, the overall microbial metabolism will shift towards anoxygenic and then deep anaerobic low-potential conditions. Thus, aerobic microorganisms will create anoxygenic conditions due to the consumption of O\({}_{2}\), and then anaerobic microorganisms should create low-potential ones (Eh = -300... -200 mV) via the fermentation of organic compounds. During fermentation, due to the accumulation of alkaline end metabolites (S\({}^{2-}\), NH\({}_{3}\) etc. ), an increase in pH is also expected. To verify the proposed approach, it is advisable, first of all, to test the effect of each physicochemical suppressive factor, and then their combined action on Rhizoctonia using a diversified microbiome. Finally, it is assumed that soil flooding and organic amendments are necessary and sufficient conditions for the strong suppression or death of _Rhizoctonia solani_ AG 2-2 IIIB. Here, we highlighted the key conditions affecting the growth of _R. solani_ AG 2-2 IIIB. They are as follows: pH, Eh, and presence of O\({}_{2}\). According to thermodynamic calculations, control of _R. solani_ AG 2-2 IIIB growth can be achieved via the creation of the described conditions. In this regard, two directions of the investigation were conducted.