Water scarcity severely limits crop productivity in arid and semi-arid regions, highlighting the need for innovative soil management strategies to enhance plant performance and maintain soil health under limited water. However, field-based evidence combining mineral-rich by-products with biodegradable organic amendments remains limited, especially in cereal systems under drought stress. A two-year field experiment (S1 and S2) was conducted using a randomized design with three replicates per treatment, each plot covering 1.2 m². Five treatments were evaluated: Control (T^-), recommended NPK, steel slag (S, 700 kg ha^-1), green waste compost (OA, 4000 kg ha^-1), and their combination (S_OA), under well-watered (100% ETc) and drought stress (30% ETc) conditions. Application rates were previously optimized in greenhouse trials. Compost, derived from plant residues, contained 20% organic carbon, 700 ppm available phosphorus, 1.5% total nitrogen, and 0.5% potassium, while steel slag from a Moroccan steel industry contained 0.37% P₂O₅, 30.6% CaO, and 8% SiO₂. A two-way ANOVA was used to assess treatment effects. Under drought, the combined application (S_OA) significantly improved soil fertility, increasing organic matter (by 183% in S1 and 111% in S2), total nitrogen (by 69% in S1 and 96% in S2), and available phosphorus (by 103% in S1 and 94% in S2) compared with the control. Durum wheat exhibited enhanced drought tolerance, with higher photosynthetic efficiency (+5.13% in 2023 and +4.78% in 2024), relative water content (+24% in S1 and +27% in S2), and grain yield (+68% in S1 and +59% in S2). Grain protein and nitrogen contents increased by 51% and 35% in S1 and 42% and 35% in S2, respectively. Heavy metal analysis in grains showed no significant differences between untreated and treated plants, confirming the environmental safety of the amendment. Nonetheless, further studies are needed to evaluate long-term metal accumulation in soil and economic feasibility at larger scales.