Mitigation of CaCO₃ Influence on <i>Ipomoea batatas</i> Plants Using <i>Bacillus megaterium</i> DSM 2894

The application of PGPB is considered a surrogate approach to reducing the amounts of phosphorus fertilizers applied in addition to its role in improving nutrient availability under stress conditions. The objective of this study was to evaluate five levels of calcium superphosphate (CSP); ultimately, CSP was applied in five levels: CSP₂₀, CSP₄₀, CSP₆₀, CSP₈₀, and CSP₁₀₀ were applied at 69, 138, 207, 276, and 345 kg ha⁻¹, respectively, and two treatments of <i>Bacillus megaterium</i> DSM 2894 (with and without) were applied on sweet potato (Beauregard cv.) plants grown in calcareous soils in the 2019 and 2020 seasons in Egypt. Some macro- and micronutrient (i.e., nitrogen (N), phosphorus (P), calcium (Ca), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu)) uptake, antiradical power (ARP), and protein and total root yields (TRYs) were determined. The plants inoculated with <i>B. megaterium</i> DSM 2894 had increased leaf N, P, and Mn contents in both seasons; in addition, Ca was increased in the second season. Furthermore, all of the root nutrient contents (except N) as well as the ARP and TRY were increased in both seasons as compared with those of the noninoculated plants. On the other hand, the maximum values of the leaf Ca, Fe, and Cu contents and the root Ca, Fe, and Zn contents were recorded with the CSP₂₀ treatment in both seasons. CSP₆₀ was the superior treatment for N (in the leaves), Mn (in the roots), ARP, protein contents, and TRY in both seasons and for the leaf Zn content in the 2019 season. The application of the CSP₁₀₀ treatment gave the highest values for the leaf and root P contents and the root Cu contents in both seasons as well as for the leaf Mn content in the first season and the root N content in the 2020 growth season. Thus, it was concluded that the application of CSP₂₀, CSP₆₀, and CSP₁₀₀ treatments with the <i>B. megaterium</i> DSM2894 mixture gave the best values compared to the use of CSP or DSM2894 individually to attenuate CaCO₃-induced damage.