Effects Of Reduced And Staged Nitrogen Application Yield And Nitrogen Use Efficiency Of Avena Sativa L. Cv. Qing Hai

At present,excessive application of nitrogen fertilizer is common in China,resulting in waste of resources and soil degradation.Against this background,it is very important to reduce the amount of nitrogen fertilizer.The operation and research mode of nitrogen fertilizer in the eastern agricultural area of Qinghai Province is relatively single,resulting in low nitrogen utilization rate and environmental pollution.In order to explore the suitable nitrogen fertilizer operation model in Qinghai area,taking’Avena sativa L.cv.Qinghai’as the experimental material,three nitrogen application levels of 69 kg·hm^-2（field conventional nitrogen application,pure nitrogen）,51.75kg·hm^-2 and 34.5 kg·hm^-2 were set;at the same time,design all base application,sowing date and jointing stage topdressing nitrogen fertilizer（the ratio of nitrogen application was 3:7）,the effects of reduced and staged nitrogen application on yield growth,photosynthetic characteristics,quality and nitrogen use efficiency of oat were systematically studied.The main results are as follows:（1）The aboveground biomass,spikelets per plant and grains per panicle of oat were significantly increased with 75%n applied by stages compared with conventional n applied by one-time base application.The yield of seed and straw increased by 4.28%and 2.34%,respectively.In addition,the contents of neutral detergent fiber,acid detergent fiber and crude fiber in stem,leaf and ear were the lowest.（2）The plant height,stem diameter,leaf area and photosynthetic physiological indexes of oat at heading stage,flowering stage and milk stage were significantly increased by 75%n application in stages compared with conventional n application at one-time base application.At the same time,with the increase of nitrogen application rate,plant height,stem diameter,leaf area,chlorophyll content,net photosynthetic rate and transpiration rate of oat increased,while intercellular CO2concentration decreased.In addition,the growth and photosynthetic characteristics of oat during heading,flowering and milk ripening were consistent.（3）Nitrogen reduction and application periods had significant effects on the nitrogen content of aboveground organs of oats at different growth stages,and the effect of nitrogen level was greater than the number of nitrogen application.From heading stage to maturity stage,nitrogen application treatment can significantly improve the nitrogen content of oat organs,and the nitrogen content of 69 kg·hm^-2nitrogen application treatment is the highest.Under the same nitrogen application rate,the nitrogen content of aboveground organs of oats could be significantly increased by stage fertilization at sowing and jointing stages.（4）Nitrogen application level and period had significant effects on nitrogen use efficiency of oat.Among them,there were significant differences in nitrogen use efficiency of oats at different nitrogen levels.The nitrogen use efficiency of oats was the highest at the nitrogen application rate of 69 kg·hm^-2.At the same time,under the same nitrogen application level,phased fertilization at sowing stage and jointing stage can also significantly improve the nitrogen use efficiency of oats.