Valorization of Steel Slag as a Soil Amendment to Boost Olive Drought Tolerance

This study examines how drought stress influences key physiological processes in olive plants and aims to determine whether slag can lessen the adverse effects of water limitation in Olea europaea cv. Nabali. Olive plants subjected to drought stress at 50% and 20% field capacity (FC) were treated with steel slag prepared at 600 °C at different concentrations, including slag treatment 1 (S1, 0.5 mg L^-1), slag treatment 2 (S2, 1.5 mg L^-1), and slag treatment 3 (S3, 2.5 mg L^-1); plants receiving 0 mg L^-1 were used as the control. The results revealed that olive plants exposed to drought stress experienced decreased growth, reduced chlorophyll content, as well as lower levels of chlorophyll fluorescence (Fv/Fm) and chlorophyll stability index (CSI). Moreover, these drought stressed olive plants exhibited higher levels of proline, malonaldehyde (MDA), and total soluble sugars. However, the application of slag to the olive plants mitigated the adverse effects of drought stress. It led to increased chlorophyll content, enhanced chlorophyll fluorescence (Fv/Fm) and CSI, while decreasing proline, total soluble sugars, and MDA content. Furthermore, the introduction of slag triggered the influence of antioxidant enzyme activities (Superoxide dismutase (SOD), Catalase (CAT), Ascorbate peroxidase (APX)) when drought stress was imposed. In conclusion, this study demonstrates that exogenous application of slag can counteract the detrimental impacts of drought on olive plants. Taken together, it highlights the potential of slag as a beneficial treatment in drought stress management for olive cultivation.