Summary:

The effects of bacterial and fungal inocula on the growth, yielding, and nutritional status of apple trees was evaluated in 3-years experiment (2018 - 2020). The experiment included the following treatments: (i) control (unfertilized soil), (ii) no fertilization + soil application of fungi, (iii) no fertilization + soil application of bacteria. The mixture of beneficial fungi contained two species: Aspergillus niger and Purpureocillium lilacinum. The mixture of beneficial bacteria contained three strains of Bacillus (Bacillus sp., Bacillus amyloliquefaciens and Paenibacillus polymyxa). The application of beneficial microorganisms (especially bacterial strains) to the soil (without additional mineral fertilization) enhanced the growth of the apple trees. In the third year of the study (2020), the trees grown in the plots inoculated with bacteria bloomed the most intensively. Plant nutritional status (expressed as concentrations of elements in leaves) was not affected by the application of the bacterial strains or filamentous fungi. The stronger growth of trees in the plots where the bacteria were used was likely related not so much to the nutritional status of the trees, but to the mitigation of the influence of the negative factors that cause the replant disease.