The Role of Cellulose Charge and Matrix Composition on KNO₃‑Nutrient Release Kinetics and Mechanisms

The global demand for food is driving research into regenerative agriculture, particularly the development of enhanced efficiency fertilizers (EEFs) that aim to improve nutrient use efficiency and reduce environmental impact. Understanding the release mechanisms of EEFs is essential for designing more effective formulations. This study examines the nutrient release kinetics of EEFs, focusing on potassium nitrate (KNO₃) embedded in a cellulose-based matrix produced via spray-drying and melt-processing. Several mathematical models - Zero-order, First-order, Higuchi, Korsmeyer-Peppas, Peppas-Sahlin, Hixson-Crowell, and Hopfenberg - were used to analyze nutrient release dynamics in water. The results showed that the matrix structure, particle formation method, and CNF charge influence the release mechanism. The Korsmeyer-Peppas and Peppas-Sahlin models best described the anomalous release behavior. K⁺ release is primarily driven by diffusion, and NO₃ ^- release is governed by matrix relaxation when combined with positively charged CNF (CNF⁺). In contrast, K⁺ is released via matrix relaxation and NO₃ ^- via diffusion when combined with negatively charged CNF (CNF^-). Adjusting CNF charge or matrix composition can optimize nutrient release, improve fertilizer management, and enhance sustainability in agricultural practices.