Calcareous soil makes up 30% of the world’s agriculture land. Horticultural crops, especially fruit trees, are susceptible to calcareous soil. Rootstocks and cultivars that are resistant to lime are used in places where fruit is grown on calcareous soil. Plant growth promoting rhizobacteria (PGPRs) have come into greater use in recent years for improving plant growth conditions such as amending poor soil. This research conducted on plants of the ‘Chester’ and ‘Jumbo’ blackberry cultivars growing in high calcareous soil conditions aimed to investigate how four different PGPR species (Alcaligenes feacalis, Microbacterium esteraromaticum, Rhizobium radiobacter, Kocuria rhizophila) affected levels of hydrogen peroxide (H2O2), malondialdehyde (MDA), antioxidant enzyme activities (Catalase, Peroxidase, Superoxide dismutase). Although there were significant statistical differences between rhizobacteria treatments, blackberry varieties were not statistically significant in all enzymes examined in terms of bacterial applications. T11 treatments had the highest values in catalese (CAT), superoxide dismutase (SOD) and peroxidase (POD) enzymes, both in the general data of blackberry and in the data of varieties. T11 treatment has the highest concentration of CAT (741.51 EU g−1 FT), POD (41,796.76 EU g−1 FT), and SOD (3375.55 EU g−1 FT), whereas T8 has the lowest content of H2O2 (24.51 mmol kg−1 FT) and MDA (12.85 nmol mL−1 FT). A positive and high correlation was detected between H2O2-CAT, H2O2-POD, H2O2-MDA, MDA-POD, MDA-SOD, POD-CAT, and POD-SOD. The results imply that the 637Ca, SY48, and SK63 bacterial strains used in combination can be recommended for use in fruit growing on calcareous soil.