Effect of Commercial Microbial Preparations Containing Paenibacillus azotofixans, Bacillus megaterium and Bacillus subtilis on the Yield and Photosynthesis of Winter Wheat and the Nitrogen and Phosphorus Content in the Soil

The present state of knowledge and biotechnological advances have allowed the potential of microorganisms to be used effectively in crop cultivation. A field study on the use of commercial bacterial preparations in the cultivation of winter wheat (Triticum aestivum L.) was carried out in the years 2017–2019 at the Educational and Experimental Station in Tomaszkowo (53°71′ N, 20°43′ E), Poland. This study analysed the effect of commercial microbial preparations containing Paenibacillus azotofixans, Bacillus megaterium and Bacillus subtilis, applied during the winter wheat growing season, on the grain yield, protein content, leaf greenness index (SPAD), the course of photosynthesis and the N-NO3, N-NH4 and P contents in the soil. The highest grain yield was noted following the application of mineral fertilisation and the three microbial preparations in combination (Paenibacillus azotofixans, Bacillus megaterium and Bacillus subtilis), as well as NPK with Paenibacillus azotofixans, in relation to mineral fertilisation alone (by 19.6% and 18.4%, respectively). The microbial preparations had a significant effect on the leaf greenness index (SPAD) at both test dates. No interaction was recorded between the years of study and the preparations applied on the SPAD values. The highest leaf photosynthetic index at both observation dates was noted for the application of NPK + P. azotofixans, as well as for NPK and all the preparations combined (P. azotofixans, B. megaterium, B. subtilis). The highest N-NO3, N-NH4 and P contents in the soil were obtained using NPK and all microbial preparations combined. Strong correlations were found between the SPAD index and the photosynthetic index value and the protein content in wheat grains and between the N-NO3, N-NH4 and P contents in the soil and the wheat grain yield.