Effect of nitrogen levels on grain yield and quality in improving mid-season japonica rice varieties

Background: Nitrogen application is recognized as a principal factor influencing rice quality. However, there remains a paucity of research on the effects of different N levels on quality, particularly within the context of the improvement of rice varieties.

Results: This study examined 14 mid-season japonica rice varieties cultivated in Jiangsu province over the past 80 years under five N application levels (0, 90, 180, 270, and 360 kg N ha^-1). The results showed that yield increased steadily as varieties improved at all N levels. For varieties from the 1950s to the 1990s, yields initially rose and then declined as N application rates increased, peaking at 270 kg N ha^-1. In contrast, modern varieties (post-2000) exhibited a consistent increase in yield with higher N application rates. Fitted equations indicated that maximum yields were achieved at optimal N levels of 237-278 kg N ha^-1 for varieties from the 1950s-1990s and 229.25 kg N ha^-1 for post-2000 varieties. As varieties improved, the content of brown, milled, and head milled rice, as well as albumen, gluten, and overall quality, increased. Conversely, chalkiness, protein content, gliadin and amylose content decreased, whereas gel consistency, breakdown, peak viscosity, and globulin showed no consistent pattern. Likewise, there was no consistent pattern in the tendency of starch to retrograde (as indicated by 'setback' values). Increasing N application rates enhanced the content of brown and milled rice, chalkiness, protein and its components, and the tendency of starch to retrograde (indicated by higher setback values). In contrast, amylose content, gel consistency, breakdown, peak viscosity, and overall taste quality declined with higher N levels. The study compared rice varieties with high yields (exceeding 10 t ha^-1) and good comprehensive taste scores (above 52), revealing that modern varieties Wuyunjing 24, Lianjing 7, Yanjing 4038, and Nanjing 9108 performed exceptionally well with 180 kg N ha^-1 and 270 kg N ha^-1.

Conclusion: Modern varieties, with optimal N application and management, can achieve both high yield and good quality effectively. © 2024 Society of Chemical Industry.