Substrate Properties, Vegetative Growth, Chlorophyll Content Index and Leaf Mineral Content of Sweet Cherry Maiden Trees as Affected by Rootstock and Plant Growth-Promoting Rhizobacteria

Sweet cherry (Prunus avium L.) is a valuable fruit crop for fresh consumption. Due to its early availability in season, it achieves relatively high prices on the market. Self-fertile cultivar Lapins is one of the world’s leading sweet cherry varieties. Intensive cherry production seeks for new technologies such as using more adaptable rootstocks and microbiological products that could help plants adopt more sustainable growth in different soils/climates. The aim of this work is to determine the substrate properties, vegetative growth, leaf chlorophyll and mineral content of maiden trees grafted on three different rootstocks due to the application of growth-promoting rhizobacteria. A pot experiment was carried out on one-year-old maiden trees of cv. Lapins grafted on SL 64, MaxMa 14 and Gisela 5 and grown in 12 L plant pots filled with commercial substrate. Plant growth-promoting rhizobacteria Azospirillum brasilense was added by watering the plants with 1.12 g L−1 per pot once a month (T1) or every two months (T2) from March to September with seven treatments in T1 and four treatments in T2. At the same time, control (C) plants were watered with rainwater. Plant height, trunk circumference and leaf chlorophyll content index (CCI) were measured. In addition, shoot growth and internode number were measured in three development stages (BBCH 34, 39 and 91). The substrate and leaf samples were collected and analyzed in the laboratory in accordance with established procedures. Data were processed by ANOVA and the Tukey test. Results have showed that rootstock affected substrate electrical conductivity (EC); nitrate (NO3−), phosphorous (P2O5), calcium (Ca) and magnesium (Mg) content, including mineral nitrogen (N) content; tree height, circumference, shoot length and internode number; the leaf chlorophyll content index (CCI); and leaf potassium (K), Ca and Mg content. Furthermore, treatment significantly affected the CCI, average internode length, ammonia (NH4+) and Ca content in the substrate and leaf N, Ca and Mg content. Rhizobacteria A. brasilense can be used as an additional biofertilizer in sustainable agricultural practices for obtaining healthier sweet cherry maiden trees, but microbial biotechnology rules must be respected.