Comparative Evaluation of Conventional Fertilizers and Slow-Release Fertilizers: An Integrative Revie

Conventional nitrogen (N), phosphorus (P), and potassium (K) fertilizers have been essential for global crop production, yet their rapid solubility often results in low nutrient-use efficiency (NUE) and significant environmental losses. Slow-release fertilizers (SRFs), including controlled-release fertilizers (CRFs), were developed to synchronize nutrient availability with crop demand, thereby improving NUE and reducing losses via leaching, volatilization, and greenhouse gas emissions. This review synthesizes empirical findings from 2000–2024 comparing conventional fertilizers (CFs) and SRFs/CRFs across nutrient dynamics, crop yield and quality, environmental impacts, technological advances, and economic considerations. Evidence shows SRFs can increase NUE by 15–50%, reduce nitrate leaching by ~36%, reduce ammonia volatilization by up to 80%, and maintain or enhance yields in many crops. However, challenges such as high production cost, variability in release rates, limited multi-year data, and concerns regarding polymer residues constrain adoption. Future research must focus on biodegradable coatings, modeling release kinetics under field conditions, long-term soil health impacts, and policy frameworks to incentivize sustainable nutrient management. Overall, SRFs represent a promising tool in sustainable agriculture but not a complete substitute for integrated soil fertility strategies.