Effects of postponing nitrogen application and organic fertilizer substitution on yield, nitrogen uptake and utilization in rapeseed

In order to explore the optimal nitrogen application for high and stable yield of rapeseed, a field experiment was conducted to analyze no fertilizer (CK), conventional fertilizer (CF: the ratio of nitrogen-based fertilizer, overwintering fertilizer and bolting fertilizer is 6∶2∶2), postponing nitrogen application (CR: The ratio of nitrogen-base fertilizer, overwintering fertilizer and fleecing fertilizer was 5∶3∶2) and postponing nitrogen application+organic fertilizer replacement 30% (CRM) on rapeseed yield and nitrogen uptake and utilization.The results showed that the rapeseed grain yield under no fertilization only maintained 30%~36% of that under fertilization.Under fertilization, compared with CF treatment, CR and CRM treatments reduced plant height, productive branch height and productive number of horns per plant in the main sequence, but increased stem thickness, productive number of secondary branches, productive number of primary horns per plant, productive number of secondary horns per plant and 1 000-grain weight of rape.CR and CRM treatments significantly increased grain yield by 23.8% and 11.7%, enhannced cumulative N uptake by 25.0% and 20.8%, improved N uptake efficiency by 27.9%~33.6%, and increased N agronomic efficiency by 14.6%~37.0%, respectively.It is an effective way to optimize fertilization for rapeseed, which can promote the growth of rapeseed secondary branches, increase the number of branch siliques, and increase nitrogen uptake and utilization.