Effects of Nitrogen Application on Nitrogen Absorption and Utilization of Direct Sowing Rapeseed(Brassica napus L.) in Paddy Rice Field

[Objective] The purpose was to study the effects of nitrogen application amount on nitrogen absorption and utilization of rapeseed,and provide a theoretical and practical basis for the precise and quantitative nitrogen fertilization of direct sowing rapeseed in paddy rice field.[Method] The dry weight and nitrogen content of double low rapeseed variety Yangyou No.6 were measured at beginning flower and maturity stage under different nitrogen application treatments(0,45,90,135,180,225,270,315 and 360 kg/hm2).[Result] With nitrogen application amount increasing,nitrogen absorption amount and utilization rate showed a trend of firstly increasing and then decreasing respectively,fitting a quadratic curve relation.When nitrogen application amount was less than 110 kg/hm2,nitrogen absorption amount and utilization rate both showed the increasing trend with increasing nitrogen application amount;When nitrogen application amount was 110-315 kg/hm2,with nitrogen application amount increasing,nitrogen absorption amount still showed a increasing trend,while nitrogen utilization rate showed a decreasing trend;When nitrogen application amount was more than 315 kg/hm2,they both showed a decreasing trend with nitrogen application amount.There was a quadratic curve relation between seed yield and nitrogen application amount,and nitrogen application amount obtaining the highest yield was 278 kg/hm2.When nitrogen application amount was 278 kg/hm2,nitrogen absorption amount and utilization rate were 209.90 kg/hm2 and 20.01 g(seed)/g(N),and comparing with the biggest nitrogen absorption amount 211.78 kg/hm2 and 20.88 g(seed)/g(N),those obtaining the highest yield were decreased by 0.89% and 4.17% respectively.[Conclusion] Rapeseed's nitrogen application amount obtaining the highest nitrogen absorption amount and utilization rate is 315 and 110 kg/hm2 respectively.That rapeseed's nitrogen application amount of 278 kg/hm2 can coordinate the relationship between nitrogen absorption and utilization and achieve the highest seed yield.