Effects of Seedling Arrangement and Nitrogen Fertilization on Pasting Properties of High‐Quality Hybrid Rice and Their Relationships With Amylose and Protein Contents

ABSTRACT Background and Objectives Pasting properties are important indicators of rice eating quality and are influenced not only by varietal differences in grain composition, such as amylose and protein content, but also by agronomic practices. This study aimed to investigate the effects of seedling arrangement and nitrogen (N) fertilization on the pasting properties of recently developed high‐quality hybrid rice, and to determine whether these effects were mediated through changes in amylose or protein content. Two high‐quality hybrid rice varieties were grown under two seedling arrangement treatments—the locally recommended pattern (two seedlings per hill with a spacing of 30 cm × 12 cm) and a potentially altered pattern (four seedlings per hill with a spacing of 30 cm × 24 cm)—and four N treatments: no N fertilization and 150 kg N ha –1 distributed at basal, early‐tillering, and panicle initiation stages with split ratios of 7:3:0, 5:3:2, and 3:4:4. Findings Seedling arrangement had no consistent impact on any pasting parameter across the two varieties. In contrast, N fertilization, regardless of split ratio, significantly decreased peak and breakdown viscosities while increasing setback viscosity in both varieties, with changes ranging from 6% to 31%. These changes were not significantly related to variations in amylose content but were strongly associated with increases in protein content, which explained over 60% of the variation in each viscosity parameter. Conclusions The altered seedling arrangement pattern did not consistently affect pasting properties in high‐quality hybrid rice. In contrast, N fertilization adversely affected pasting properties, primarily by increasing protein content. Significance and Novelty This study provides practical guidance for high‐quality hybrid rice production, suggesting that adopting the altered seedling arrangement pattern is unnecessary, whereas N fertilization poses a challenge for maintaining or improving eating quality.