Effects of application of nitrogen on seed yield and quality of winter oilseed rape（Brassica napus L.）

To explore the effects of N fertilizer rates on seed yield and quality of winter rapeseed, field experiments were carried out in Wuxue County, Hubei Province during 2019/2020 and 2020/2021 seasons. The experiments were set at five nitrogen application levels of 0, 90, 180, 270, and 360 kg N hm–2. Rapeseed yield, N concentration, and rapeseed quality indexes were measured at maturity stage. The results showed that N application significantly increased rapeseed yield and N content. Compared with the zero N application, the average yield increase after N application was 1548 kg N hm–2, and the average yield increase rate was up to 32.9%. Within the range of N application rate of 0–270 kg N hm–2, rapeseed yield increased significantly with the application of N fertilizer. If N application was continued, rapeseed yield did not change significantly or had a downward trend. N application mainly improved rapeseed yield by increasing the number of pods per plant. N application significantly increased protein content i