Evaluating the Growth Dynamics and Grain Quality Interrelationships in Rice as Modulated by Establishment Methods: A PCA Approach

Background: Rice establishment practices can influence early crop growth and may affect grain quality, yet their relationships in the cultivar Shatabdi under Upper Brahmaputra Valley conditions remain insufficiently documented. Aims: To study the interrelationships between three rice establishment methods (dry direct seeding, wet direct seeding and transplanting), the growth dynamics and grain quality of rice cv. Shatabdi, and to explore the relationships among these traits using correlation and principal component analysis (PCA). Study Design: A split-plot design with three replications, with establishment methods assigned to the main plots (results were averaged over the sub-plot nitrogen treatments). Place and Duration of Study: Instructional-cum-Research Farm, Assam Agricultural University, Jorhat, Assam, India, during the kharif seasons of 2024 and 2025. Methodology: Relative growth rate (RGR) and net assimilation rate (NAR) were calculated at 30-day intervals, i.e., 30–60, 60–90 and 90–120 days after sowing (DAS). For the grain quality parameters, amylose content, amylopectin content and gelatinisation temperature were determined. Data were analysed using ANOVA with Tukey’s HSD (p < 0.05), while Pearson correlation and PCA were performed on six establishment-method-by-year means. Results: The establishment method significantly influenced RGR at 30–60 DAS: transplanting (0.067 and 0.068 g g-1 day-1) exceeded wet DSR (0.063 and 0.064) and dry DSR (0.059) in 2024 and 2025, respectively. No significant differences were observed in RGR at later stages, NAR at any stage, amylose content (22.70–23.32%), amylopectin content (76.41–77.24%) or gelatinisation temperature (70.82–72.60 °C). In the correlation analysis, RGR at 60–90 DAS was negatively correlated with NAR at 90–120 DAS (r = −0.89, p = 0.017). The first three principal components explained 88.5% of the variance, and PC1 separated dry DSR from wet DSR. Conclusion: The early growth advantage of transplanting disappeared by 60 DAS, and grain quality was unaffected by the establishment method. Dry DSR and drum seeding are therefore viable alternatives to transplanting for Shatabdi.