Effects of nitrogen application on grain‐filling characteristics and quality of rice

Abstract BACKGROUND In rice production, nitrogen fertilizer plays a crucial role, influencing not only the growth and development process but also the quality and yield of rice. Therefore, studying rational nitrogen application strategies provides a theoretical basis for improving rice yield and quality. A 2‐year field experiment was conducted using the rice varieties Tianlongyou 619 and Liaojing 419. The study examined the effects of two nitrogen levels (N1, 160 kg hm −2 ; N2, 240 kg hm −2 ) and three nitrogen application modes (T1, basal fertilizer:tiller fertilizer:panicle fertilizer = 5:4:1; T2, 4:3:3; T3, 3:2:5), along with a control treatment without nitrogen application (N0), on rice grain‐filling characteristics and quality. RESULTS Nitrogen application accelerated the grain‐filling rate and intensity. The active grain‐filling period of inferior grains for both varieties extended with increasing nitrogen application. Under different treatments, the grain weight during the rapid filling stage was consistently higher in N1 than in N2 for both varieties. The N1T3 treatment reduced the soluble starch synthase content in both varieties, while their starch branching enzyme and ADP‐glucose pyrophosphorylase levels were highest under N1T3. Analysis of starch content during grain filling revealed that starch synthase activity peaked at 15 days, and the starch accumulation rate reached its maximum between 15–20 days after flowering. Delayed nitrogen application improved starch accumulation in superior grains to varying degrees. CONCLUSION Overall, both varieties achieved superior quality under a nitrogen application rate of 160 kg hm −2 with a fertilizer management ratio of basal:tiller:panicle fertilizer = 3:2:5. In 2022, under N1T3 treatment, Tianlong You 619 and Liaojing 419 achieved taste values of 69.8 and 75.9, and balance degree of 6.6 and 7.57, respectively. © 2026 Society of Chemical Industry.