Screening rice varieties for enhanced nitrogen use efficiency and yield based on root trait evaluation

Nitrogen (N) fertilizers have played a significant role in enhancing rice yield over recent decades; however, their excessive use has also led to considerable negative environmental impacts. To achieve sustainable productivity, it is essential to adopt strategies that enhance yield while reducing, or at least minimizing, nitrogen input, thereby improving nitrogen use efficiency (NUE). The crucial physiological reasons for maintaining high yield and NUE in N-efficient varieties were attributed to better root system characteristics. Fourteen selected rice varieties, comprising both short-duration and medium-duration varieties, were screened for NUE based on root characteristics under field conditions at two levels of the recommended dose of nitrogen (RDN). Application of 100 % RDN resulted in a significantly higher root volume and Root dry weight. Interaction effects also showed significant influence. Based on the Root Dry Weight Efficiency Index (RDWEI), seven varieties were classified as efficient (RDWEI > 1.0). At the same time, the remaining seven were moderately efficient (RDWEI 0.5–1.0) and none of the varieties were N inefficient (RDWEI <0.5). Trends in RDWEI were consistent with variations in grain yield, highlighting its reliability as a NUE indicator. Among the evaluated varieties, Harsha recorded the highest grain yield (4.1 t ha⁻¹), which was statistically comparable to Varsha, Aiswarya and Sreyas. Notably, varieties that maintained stable yields under reduced N application demonstrated superior adaptability and NUE. The study confirmed that genetic variability exists in N response, and the interaction between variety and N levels significantly influenced yield and root traits. Identifying N-efficient genotypes with robust root systems presents a promising approach for enhancing N management and promoting sustainable rice production, as well as improved soil health.