The investigation of P, K and Si mobilization dynamics in greenhouse ground with the application of selective microorganisms and diatomite was the purpose of this work. The substrate for laboratory research was ground (peat and perlite mixture-PP), diatomite (D) and bacterial preparations, which were introduced into the ground. Four bacteria isolated of environment places: from soils-Bacillus macerans and Bacillus circulans and from surface of sand-Bacillus circulans 2 and Corynebacterium sp. have been applied as a basis of bacterial preparations. Experiment included 10 variants: two grounds (PP and PPD) and 8 variants with treating ground of each of four bacterial preparations. The results showed that the content of water-soluble elements forms in a ground with microorganisms after 56 days has increased: P and K-in 10 times, Si-in 3 times. It proved efficiency of bacterial cultures in the mobilization of these elements. The most active microorganisms were those that have been isolated from surface of sand (Corynebacterium sp. and Bacillus circulans 2). The mixture of ground and diatomite showed the best efficiency. The best ground microbes' community was investigated using chemo diagnostic method gas chromatography-mass spectrometry. It has been shown that the content of Acetobacterium sp. (the culture capable to formation of acetic acid in an anaerobic metabolism), had increased to the end of composting period in 10 times and the number of Bacillus sp.-as minimum in 100 times.