12 Nanofertilizers for Enhanced Nutrient Use Efficiency (NUE) in Crop Production Adarsh Dangwal1*, Rajeew Kumar1, Priyanka Pandey1 1Department of Agronomy, G.B. Pant University of Agriculture & Technology, Pantnagar, Uttarakhand, India 2Department of Molecular Biology and Genetic Engineering, Pantnagar, Uttarakhand, India *Corresponding author mail: adarshdangwal04@gmail.com DOI : 10.5281/zenodo.20531637 Abstract Global agriculture faces the dual challenge of increasing food production while minimizing environmental degradation associated with inefficient fertilizer use. Conventional fertilizers exhibit low nutrient use efficiency (NUE), with substantial proportions of applied nitrogen, phosphorus, and potassium lost through leaching, volatilization, runoff, and soil fixation, contributing to eutrophication, greenhouse gas emissions, and soil health decline. Nanofertilizers have emerged as a promising strategy to enhance NUE by delivering nutrients through nanoscale carriers, encapsulation systems, or surface-functionalized particles that enable controlled and targeted release. Their high surface area, tunable physicochemical properties, and improved interaction with plant tissues and rhizosphere processes allow better synchronization between nutrient supply and crop demand. This chapter synthesizes current knowledge on the classification, synthesis, mechanisms, agronomic performance, and environmental implications of nanofertilizers. Macronutrient and micronutrient nanoformulations, including nano-urea, nano-phosphates, nano-potassium, and metal oxide nanoparticles, demonstrate improved nutrient uptake, enhanced photosynthetic efficiency, stress tolerance, and yield gains at reduced application rates. Evidence from field and greenhouse studies indicates that partial substitution of conventional fertilizers with nanofertilizers can sustain yields while reducing nutrient inputs and greenhouse gas emissions. However, concerns regarding ecotoxicity, nanoparticle accumulation, regulatory gaps, cost, and scalability remain critical constraints to widespread adoption. Overall, nanofertilizers represent a transformative tool for precision and climate-smart agriculture, provided that long-term safety, standardized risk assessment, and robust field validation are ensured to balance productivity gains with environmental sustainability. Key Words: Controlled Release; Nanofertilizers; Nutrient Use Efficiency (NUE); Precision Nutrient Management; Sustainable Agriculture