Metallurgical slag and biofertilizers for improving durum wheat growth and water productivity under deficit irrigation in semi-arid conditions

Drought limits durum wheat productivity, particularly in arid regions. This study evaluates how metallurgical slag combined with two beneficial microorganisms influences wheat growth, physiological and biochemical responses under full irrigation (100% ETc) and sustained deficit irrigation (30% ETc). Open-field experiments were conducted during two successive seasons in Marrakech, Morocco, with a semi-arid climate. Accordingly, six treatments, namely an untreated control (CK), standard chemical fertilization (CF), metallurgical slag alone (MS), and bipartite mixtures including slag with plant growth-promoting rhizobacteria (MS_PGPR) and slag with arbuscular mycorrhizal fungi (MS_AMF), in addition to the tripartite mixture MS_PGPR_AMF, were used. Under deficit irrigation, the highest biomass was recorded with MS_PGPR_AMF and MS_AMF, while all MS-based biofertilizers improved water productivity compared to fully irrigated plants with NPK fertilization. MS_PGPR increased total chlorophyll content, surpassing the effects of MS alone, NPK fertilization, and control. Moreover, MS_PGPR_AMF enhanced plant vigor by 25% and 52% in seasons 1 and 2, respectively. Durum wheat cultivar treated with MS-based biofertilizers indicated low levels of proline and soluble sugars, reflecting reduced stress, whereas antioxidant enzyme activities were markedly upregulated. Overall, these findings suggest that the synergistic use of MS with AMF alone or combined with PGPR enhances wheat resilience under severe drought by improving water relations, antioxidant defenses, and photosynthetic efficiency. Thus, demonstrate the potential of integrating metallurgical slag with beneficial microorganisms as an eco-friendly approach to boost the productivity and resilience of durum wheat under water-limited conditions.