Apple leaf macro- and micronutrient content as affected by soil treatments with fertilizers and microorganisms

Abstract

The effects of bacterial and fungal inocula on the nutritional status of ‘Sampion’ apple trees was evaluated in three-years study (2018–2020). The experiment was set up in a two-factor system: (i) fertilization (without fertilization or mineral fertilization with nitrogen, phosphorus, potassium); (ii) application of beneficial microorganisms (without application, application of fungi or bacteria). The mixture of beneficial soil 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 analysis of mineral content and leaf greenness (SPAD index) was performed on the samples collected from the trees in August. The lack of mineral fertilization caused a significant decrease in the nitrogen content of apple leaves, which resulted in their lighter color (lower SPAD index). The application of filamentous fungi or bacterial strains had a modifying effect on the mineral composition of apple leaves, what became evident especially in the third year of the study. An increase in the concentration of nitrogen, calcium, magnesium, sulphur and most microelements (except for boron) was found as a result of the influence of tree mineral fertilization and microorganisms applied to the soil. In the absence of mineral fertilization of the trees, the applied microbial inocula resulted in the significant increase of concentration of most macro- and microelements in the leaf tissue (except for magnesium and boron).