The Role of Leaf Morphology and Sustainable Management Practices on Optimizing Nitrogen Use Efficiency of Upland Rice: A Review

Nitrogen is an essential macronutrient for plant growth, photosynthesis, and grain yield. However, the nitrogen use efficiency (NUE) of crops remains relatively low, leading to nitrogen losses and environmental concerns. This is particularly important in upland rice because it is a high nitrogen user, but research of its NUE is limited. This literature review explored the contributions of leaf morphology, specifically leaf size and leaf angle, to nitrogen utilization efficiency in upland rice under varying rates of nitrogen fertilization. It also evaluated sustainable nitrogen management practices across diverse cropping systems. Findings reveal that nitrogen fertilization significantly influences leaf development, canopy structure, and nitrogen remobilization, all of which directly affect photosynthetic efficiency and yield. Breeding strategies focusing on moderate leaf size and erect leaf angles improve the nitrogen uptake and use by rice. In addition, sustainable farming practices, including precision nitrogen management, conservation agriculture, and intercropping with legumes, are effective in enhancing NUE and reducing nitrogen losses across various rice production systems. Future research should focus on identifying the thresholds of nitrogen rates that optimize leaf morphology across diverse upland rice genotypes and unravel the genetic and physiological mechanisms linking nitrogen application to leaf development.