ABSTRACT Urea accounts for over 50% of global nitrogen fertilizer use, yet its efficiency is limited by rapid dissolution and nitrogen losses through volatilization, leaching, and gaseous emissions. This review systematically analyzes 34 peer‐reviewed studies on coating‐engineered controlled‐release urea fertilizers, selected through a Scopus‐based search and evaluated using a six‐criterion methodological framework. Approximately 41% of studies exhibit low risk of bias, while 59% are moderate, indicating generally robust but heterogeneous evidence. Most systems employ granular urea (2.5–5.0 mm) with coating thicknesses of 40–170 μm, achieving release durations from 20 to 150 days. Diffusion‐controlled release dominates (> 70%), while swelling‐ and degradation‐assisted mechanisms occur mainly in biopolymer‐based coatings. Compared with uncoated urea, coated systems reduce ammonia volatilization by 30%–90% and nitrate leaching by 40%–90%. However, only 30%–40% of studies include field validation, and fewer than 15% assess mechanical durability. The findings demonstrate that coating integrity, permeability evolution, and process control are more critical than coating thickness alone. Persistent gaps in standardized testing, scale‐up validation, and life‐cycle assessment limit comparability and practical implementation. This review provides a mechanistic framework to guide the design of efficient and sustainable controlled‐release urea fertilizers.
Jumakir et al. (Thu,) studied this question.