Vol. 7, Issue 1, Part B (2025)

Polyhalite, a naturally occurring multi-nutrient mineral containing potassium, magnesium, calcium, and sulfate, has recently attracted attention as a sustainable fertilizer source capable of addressing nutrient deficiencies in cropping systems. This study investigated the chemical pathways of sulfate (SO₄²⁻), potassium (K⁺), and magnesium (Mg²⁺) release from polyhalite under varying soil pH and textural conditions, using dissolution experiments, kinetic modeling, and soil incubation trials. Results demonstrated that nutrient release followed the order SO₄²⁻ > K⁺ > Mg²⁺, with sulfate showing rapid solubilization, while potassium and magnesium exhibited slower, sustained release patterns. Acidic conditions (pH 5.0) significantly enhanced dissolution compared to neutral and alkaline conditions, indicating pH sensitivity in release mechanisms. Kinetic analysis revealed that first-order models fitted the data more accurately than diffusion models, confirming a surface-controlled dissolution mechanism transitioning to diffusion limitation over time. Soil incubation studies further highlighted that sandy loam facilitated rapid nutrient availability but with higher leaching losses, while clay loam retained nutrients longer, ensuring extended availability. The integration of statistical analysis and mechanistic interpretation validates the hypothesis that polyhalite provides immediate sulfur nutrition alongside prolonged potassium and magnesium supply, making it a valuable component of integrated nutrient management systems. The findings underscore its role in enhancing nutrient-use efficiency, supporting sustainable crop production, and improving soil fertility management. Practical recommendations include adopting soil-type-specific application strategies, aligning fertilizer timing with crop demand, and integrating polyhalite with organic or biological inputs to optimize nutrient delivery. Overall, the research establishes polyhalite as a viable, slow-release, multi-nutrient fertilizer that can contribute to long-term agricultural sustainability and food security.