Enhanced-efficiency fertilisers: mechanisms, agronomic performance, and environmental implications with emphasis on nitrogen-based fertilisers

Enhanced-efficiency fertilisers (EEFs) are designed to regulate nutrient release and reduce losses associated with conventional fertiliser use. Among these, enhanced-efficiency nitrogen fertilisers (EENFs) have received increasing research attention, as nitrogen (N) utilisation by crops is only 30–35%, resulting in substantial environmental losses. This review focuses on EENFs, placing them in the broader context of EEFs, and outlines key fertiliser types, nutrient release mechanisms, and factors influencing their performance. In addition, a meta-analysis of 15 independent studies was conducted to quantify the effects of EENFs compared with conventional urea on cereal grain yield. Cereal grain yield was selected as the outcome because maintaining cereal production is fundamental to global food security and sustainable agriculture, and it provides a consistently reported agronomic endpoint for comparison across studies. The analysis indicates that EENFs can maintain or improve cereal grain yield compared with conventional urea. Evidence from the broader literature suggests that EENFs may reduce N losses through leaching and volatilisation. However, the magnitude of these benefits is site-specific and varies with soil and environmental conditions, management practices, and fertiliser formulation. Their advantages are generally more evident in systems prone to high N losses, whereas under lower-loss conditions, higher fertiliser costs may limit economic returns and widespread adoption. Overall, EENFs represent a practical, context-dependent approach to improving N management in agricultural systems.