Role of polyhalite in enhancing phytochemical profiles of aromatic and medicinal herbs

Polyhalite—a natural multi-nutrient mineral supplying K, Ca, Mg, and S—offers a practical route to elevate both yield and quality in aromatic and medicinal herbs, yet direct evidence linking polyhalite to phytochemical enhancement remains limited. This study evaluated the “Role of Polyhalite in Enhancing Phytochemical Profiles of Aromatic and Medicinal Herbs” using Ocimum basilicum (basil) and Mentha arvensis (mint) grown under a randomized complete block design with four nutrient regimes: Control, Conventional (N-P), Polyhalite-75 kg ha?¹, and Polyhalite-150 kg ha?¹ (n = 3). Essential oil yield (hydrodistillation), total phenolics (Folin-Ciocalteu), total flavonoids (AlCl?), and antioxidant activity (DPPH, IC??) were quantified; post-harvest soil K, Ca, Mg, and S were assessed to capture residual fertility. One-way ANOVA followed by Tukey HSD showed significant treatment effects (p < 0.05) across all phytochemical endpoints. Polyhalite produced stepwise improvements relative to Control and Conventional, with Polyhalite-150 yielding the highest essential oil output and the greatest increases in phenolics and flavonoids, alongside the lowest IC?? values, indicating superior antioxidant capacity. Soil analyses confirmed elevated post-harvest K, Ca, Mg, and S in polyhalite treatments, supporting a soil-plant mechanism consistent with improved ionic balance, photosynthate allocation, and redox-linked secondary metabolism. Collectively, the findings substantiate that balanced multi-element nutrition via polyhalite can concurrently enhance quantitative (oil yield) and qualitative (phenolics, flavonoids, antioxidant activity) attributes in basil and mint. The results provide actionable guidance for dose calibration (75-150 kg ha?¹), timing (pre-plant with optional split), and integration with modest, demand-based N and P, positioning polyhalite as a quality-oriented, sustainability-aligned fertilization strategy for high-value herbal supply chains.