关键词: 油菜, 播期, 施氮量, 产量, 产油量

Abstract:

【Objective】 Under the multi-cropping system in the Yangtze River Basin, the rapeseed sowing date was delayed, resulting in low yield and poor quality. In this study, in order to explore the effect of different nitrogen rates on the yield and seed quality of late sowing rapeseed, the related indexes of late sowing rapeseed, including yield and its components, agronomic characters, nutrient accumulation, grain quality, and so on, were measured under different nitrogen application levels in order to find out the best nitrogen rate of late sowing rapeseed. 【Method】 Field experiments were carried out in Yingcheng and Huanggang, Hubei province. A rapeseed variety“Zhongyouza19”was used as the material, and two sowing dates (S1,10th October; S2, 10th November) and 4 nitrogen rates (N0, 0; N1, 120 kg·hm^-2; N2, 240 kg·hm^-2; N3, 360 kg·hm^-2) were set in this study. 【Result】 (1) Late sowing of rapeseed significantly reduced the yield. With an increase in nitrogen rate, the pods per plant, seeds per pod and 1000-seed weight had a significant increase under different sowing dates. Compared with N0, the yield under N1, N2 and N3 was increased by 31.9%, 68.6% and 79.8% on average under normal sowing date, respectively, and increased by 36.0%, 82.0% and 87.3% on average under late sowing date, respectively. (2) With the sowing date delaying, the root crown diameter, plant height and branch height were decreased significantly, and the above-ground biomass were increased, whereas the root biomass and the root-shoot ratio were decreased. With an increase in nitrogen rate, the root crown diameter, plant height, branch height, the root and shoot biomass were increased, but the root-shoot ratio was decreased, in addition, the lodging angle were increased by 162.7%, 254.7% and 374.7% on average under normal sowing date, respectively, and increased by 105.5%, 208.7% and 303.1% on average under late sowing date, respectively. Lodging was more severe under higher nitrogen rate. (3) With the sowing date delaying, the nitrogen content and nitrogen uptake in the root were decreased. The nitrogen content in the seed was increased, but the nitrogen uptake and oil content in the seed were decreased. Then, the nitrogen content in the stem and the pod shell did not change significantly, but the nitrogen uptake increased significantly. With an increase in nitrogen rate, the nitrogen content and uptake in each part were increased and the oil yield also showed an increasing trend, but the oil yield (1 830.5 kg·hm^-2 and 1 534.5 kg·hm^-2 (Yingcheng), 1 535.1 kg·hm^-2 and 1 220.0 kg·hm^-2(Huanggang)) and the seed nitrogen use efficiency (34.88% and 31.14% (Yingcheng), 27.95% and 25.48% (Huanggang)) reached the maximum at the nitrogen rate level of 240 kg·hm^-2under different sowing dates. There was a significant positive correlation between seed nitrogen use efficiency and grain yield and oil yield, but there was no correlation with lodging angle. The grain yield and oil yield could be improved by increasing seed nitrogen use efficiency without aggravating lodging. 【Conclusion】 Increasing nitrogen rate could improve the yield of late sowing rapeseed, but the nitrogen rate should be controlled at about 240 kg·hm^-2 to further control lodging and obtain maximum oil yield.

Key words: rapeseed (Brassica napus L.), sowing date, nitrogen rate, yield, oil yield