Influence of Biofertilizers and Liming on Vetch–Oat Mixture Productivity and Change in Sod-Podzolic Soil Microbocenosis

The influence of modification of granules of organomineral fertilizer (OMF) by BisolbiFit (Bacillus subtilis Ch-13), Phosphatovite (Bacillus mucilaginosus), and PhosphoActiv (Bacillus subtilis Ch-13 + Bacillus mucilaginosus) biopreparations on the productivity of vetch–oat mixture, as well as on changes in the structure of soil microbocenosis, has been studied under the conditions of a two-factor field experiment. The research was carried out on a soddy medium podzolic light loamy soil. The experiment included six versions: control (without fertilizers); N₃₀P₃₀K₃₀; organomineral fertilizer (OMF); OMF + BisolbiFit modifier; OMF + Phosphatovite; OMF + PhosphoActive with liming (pH_KCl 5.9) and without liming (pHKCl 5.1). The fertilizers were introduced with equal portions of nitrogen (30 kg a.i./ha). On average, the highest yield increase for the period from 2015 to 2017 (11.7% with application of N₃₀P₃₀K₃₀ and 10.6% with application of unmodified OMF) was obtained in the OMF + BisolbiFit combined with liming version. The use of other modifiers increased the yield of the herbage of vetch–oat mixture only at the trend level. The use of all types of fertilizers increased the content of crude protein by 1.24–3.34% compared to the control. A trend towards an increase in the concentration of phosphorus and potassium in the herbage has been recorded. The highest yield increase per 1 kg of active ingredient (a.i.) of fertilizers was obtained with application of BisolbiFit: 18.0 kg of feed units without liming and 20.7 kg of feed units with liming. The modern method of high throughput sequencing of the 16S ribosomal RNA gene has detected the leading phylums, the share of which in the soil was significantly higher than that of the others: Acidobacteria (7.1–11.5%) and Actinobacteria (13.6–20.4%), Bacterroidetes (7.2–19.3%), Proteobacteria (45.3–56.2%), and Verrucomicrobia (4.3–10.3%). The highest proportion of Actinobacteria (15–20%) was recorded in versions with application of N₃₀P₃₀K₃₀, OMF, and OMF + BiosolbiFit and the highest proportion of the Proteobacteria phylum was recorded in the version with application of OMF + BisolbiFit, which indicates intensive nitrification processes.