Effects of Nitrogen Fertilizer Management on Biological Traits and Physiological Indexes at Seedling Stage and Yield of Directly-sown Rapeseed(Brassica napus L.)

氮肥运筹对直播油菜苗期生物学性状、生理指标及产量的影响（英文）

Field experiments were carried out to study the effects of different nitroge- napplication rates and application times on biological traits and physiological indexes of directly-sown rapeseed （Brassica napus L.） at the seedling stage and investigate the relationship between these biological traits or physiological indexes at the seedling stage and yield, so as to provide scientific theoretical support for high yield and efficient fertilization management in production of winter rapeseed. Field trials were conducted in Chengdu plain of Sichuan Province under rice-rapeseed rotation system during the period of 2011-2012. The nitrogen application rate trial consisted of five nitrogen levels （0, 90, 180, 270 and 360 kg/hm2） and the nitrogen application time trial included NTl（single application as base fertilized）, NT2 （bottom application ＋one time of topdressing at seedling stage） and NT3 （bottom application＋two times of topdressing at seedling stage） under the same nitrogen rate （225 kg/hm2）. The results indicated that compared with no nitrogen application （NO） treatment, the in- crease of nitrogen fertilizer is beneficial to the increase of biological traits including plant height, green leaf number, leaf area index and dry weight of rapeseed at the seedling stage, the improvement of physiological indexes including total nitrogen content, chlorophyll content and soluble protein content of functional leaves, and the reduction of soluble sugar content. Nitrogen rate was linearly correlated with various biological traits at the seedling stage and physiological indexes including total nitro- gen content, chlorophyll content and soluble sugar content in functional leaves over- a/I, but in parabolic correlation with soluble protein content. Under the same nitrogen rate, NT2 treatment exhibited biological traits remarkably or significantly higher than NT1 treatment and NT3 treatment. The nitrogen application times were linearly cor- related with the physiological indexes of functional leaves at the seedling stage. The various biological traits and physiological index of functional leaves at the seedlings stage were in quadratic function parabolic correlation with seed yield, and the corre- lation was significant （P〈0.05）. Therefore, under the rice-rapeseed rotation system in Chengdu plain, the economic rational nitrogen rate is 180-225 kg/hm2, and the mode of bottom application ＋ one time of topdressing （NT2） is suitable.

为探讨氮肥运筹(氮肥用量及施氮次数)对直播油菜苗期生长和产量的影响以及苗期生物学性状、生理指标与产量的关系,于2011/2012年在四川省成都平原开展了不同施氮量(0、90、180、270、360 N kg/hm^2)和同等施氮量(225 N kg/hm^2)下不同施氮次数(一次性底施、底肥+1次苗期追肥、底肥+2次苗期追肥)两个大田试验。结果表明,增施氮肥有利于促进直播油菜苗期各生物学性状(株高、绿叶数、叶面积指数和干物重)和增加产量,提高功能叶全氮含量、叶绿素含量和可溶性蛋白含量等生理指标,降低可溶性糖含量。施氮量与苗期各生物学性状以及功能叶全氮含量、叶绿素含量和可溶性糖含量等生理指标均总体上呈线性关系,而与可溶性蛋白含量呈抛物线关系。同等施氮量下,NT2(底肥+1次苗期追肥)处理的苗期生物学性状明显或显著高于NT1(一次性底施)处理、NT3(底肥+2次苗期追肥)处理。施氮次数与苗期功能叶生理指标呈线性关系。直播油菜苗期各生物学性状指标和功能叶生理指标均与籽粒产量呈二次函数抛物线关系,相关性均达到显著(P<0.05)。在成都平原稻油轮作体系条件下,直播油菜高产高效栽培的经济合理施氮量为180-225 N kg/hm^2,且适当减少施氮次数(分底肥+1次苗期追肥两次施氮),有利于冬前苗期维持适宜的株高、单株绿叶数、叶面积指数和群体干物重等生物学性状以及全氮含量、叶绿素含量、可溶性糖含量和可溶性蛋白含量等生理指标。