A review on smart nitrogen fertilizers for sustainable agriculture: Integrating biomaterials and additive manufacturing

Increasing global food demand, nitrogen losses, and greenhouse gas emissions underscore the need for enhanced-efficiency nitrogen fertilizers (EEFs) that improve nitrogen use efficiency (NUE) while reducing environmental impacts. Achieving sustainable agriculture requires effective and environmentally compatible nitrogen management strategies that improve nitrogen-use efficiency while minimizing environmental impacts. This review summarizes advances in smart nitrogen delivery systems that integrate biomaterials (e.g., polysaccharides, proteins, biochar, and biopolymer hydrogels) with additive manufacturing (AM) to tailor release kinetics, spatial distribution, and responsiveness to soil and plant conditions. By enabling the integration of biodegradable materials with digitally programmable geometries and internal architectures, additive manufacturing offers a fundamentally new pathway for regulating nutrient release kinetics and achieving site-specific nutrient delivery. Recent advancements in additive manufacturing-enabled slow-release fertilizers are reviewed with a focus on architecture-enabled nutrient control as a distinguishing advantage over conventional formulation-driven systems. Although additive manufacturing remains in an early stage of adoption for fertilizer development, recent studies indicate that it enables precise modulation of material composition and structural architecture, allowing controlled nutrient-release behaviors that are challenging to achieve with traditional fertilizer technologies. By synthesizing progress in biodegradable materials, additive manufacturing, and sustainable agronomic principles, this review identifies additive manufacturing-enabled slow-release fertilizers as a promising platform for efficient and environmentally responsible nitrogen delivery. We Conclude by outlining key research challenges and commercialization pathways, emphasizing the need for interdisciplinary efforts to translate laboratory-scale innovations into practical agricultural solutions.