Multivariate Assessment of Nitrogen Fertilization Effects on Yield and Growth Traits of Sesame (Sesamum indicum L.) using Principal Component and Regression Analyses

Efficient nitrogen management is critical for improving sesame (Sesamum indicum L.) productivity, yet the complex interrelationships among growth, yield, nitrogen-use efficiency, and quality traits remain poorly understood. This study aimed to identify the major nitrogen-driven determinants of grain yield in sesame using a combination of principal component analysis (PCA) and regression modeling. Analysis was performed on growth traits, yield components, nitrogen-use efficiency and grain quality attributes using the field experimental data All quantitative variables were standardized prior to PCA to reduce dimensionality and elucidate dominant patterns of variation. The contributions of key agronomic variables to grain yield were quantified using the multiple linear regression. Four principal components with an eigenvalue higher than 1 was retained by PCA, which could explain 78.77% of total variation. The axis of productivity and N-response was the first principal component (43.50%), which had high scores for leaf area index, grain yield, plant biomass, nitrogen content, agronomic efficiency, and N-use efficiency. Regression analysis showed that LAI at week-6 after sowing, plant biomass, and N-use efficiency responded significantly (p < 0.01) to grain yield while SPAD value had the strongest correlation with grain yield; however, there was no synergistic response for any of the efficiency-related variables when they were analyzed simultaneously. Traits related to plant height (vegetative hight) were sources of structural variability, but these not main factors in the determination of yield. Generally, the applied PCA and regression methods showed that sesame yield under different nitrogen levels is influenced not only by N-rate but also by canopy growth, dry matter accumulation and utilization of N. These results emphasize the use of efficiency based-nitrogen management practices to sustain sesame yield.