Agronomical And Physiological Characteristics Associated With Yield And Yield Components Of Winter Wheat As Affected By Nitrogen Managements

Inappropriately expanding the timings and rates of the nitrogen application can reduce grain yields and increase the nitrogen loss,thereby affect environmental quality.Despite the fact,grain yield response to nitrogen nutrition has been well examined,but dynamics of total dry biomass,nitrogen use efficiency,plant N content,photosynthetic characteristics and chlorophyll contents of winter wheat in response to N nutrition are not well understood.Besides this,it is not clear in what way the impacts of nitrogen rates and ratios might be progressive,or the step to which the integrative effects of nitrogen levels and ratios would mark the satisfactory response for agronomical and physiological characteristics.Furthermore,less information is available about the integrative approach of nitrogen rates and ratios which could increase yield potentials.The study was planned to examine the effects of the different nitrogen fertilization levels on photosynthetic parameters,N use efficiency,and growth and yield traits of winter wheat.Field experiments were conducted at Taigu experimental farming station of Shanxi Agricultural University,Shanxi Province,China.The experiments were established in a split-plot design,repeated thrice.Total nitrogen(N)levels,including control(No fertilizer applied)75,150,225 and 300 kg ha^-1were arranged in main plots and different nitrogen ratios were arranged in subplots as 5:5(50%,50%)and 6:4(60%,40%).Nitrogen fertilizer was applied at pre-sowing,at jointing stage,at flowering stage and grain filling stage,respectively.The experimental plots were of 12 m²(3m×4m).All the experiments for present work were conducted to investigate the impact of nitrogen fertilizer management on nitrogen fertilization on N content,leaf photosynthesis,total chlorophyll,leaf area index,grain yield on winter wheat in the calcareous cinnamon soil.The results were as follows:(1)Results revealed that in contrast to control,225 kg ha^-1significantly increased plant height,above ground biomass by 89.13%,49.39%,at grain filling stage and stem dry biomass and leaf area increase by 39.43%and 71.21%respectively at flowering stage where plants received 60%nitrogen during sowing time and 40%nitrogen at flowering stage.However,leaf area index and leaf area duration were improved under jointing stage where fertilizer was applied in 60%:40%.Grain yield of winter wheat had a significant positive correlation with winter wheat growing components.However,the negative relationship of grain yield was perceived with the photosynthetic rate.(2)Total nitrogen content in total dry matter was significantly amplified with increasing rates of nitrogen fertilizer.The average total nitrogen content was increased from 40.00-60.00%under 225 kg N ha^-1where plants received nitrogen nutrition in 60%at sowing time and 40%at jointing stage as compared to other growing stages and nitrogen rates.The maximum nitrogen content in leaves was noted 32-34 g kg^-1under 225 kg N ha^-1at jointing stage where nitrogen was applied in 6:4 ratios.Similarly,the maximum nitrogen contents in stem were recorded 13-15 g kg^-1under 225 kg N ha^-1at which plants received nitrogen nutrition in 60%at sowing time and 40%at jointing stage.(3)Furthermore,Results revealed that 225 kg N ha^-1significantly augmented stomatal conductance(Gs),photosynthetic rate(Pn),transpiration rate(Tr)and intercellular CO₂(Ci)by 28.59%,42.39%,15.26%and 10.00%at jointing and flowering stage followed by grain filling stage as compared to control.Photosynthetic rate was gradually increased as nitrogen application was applied in both years.The trend of photosynthetic characteristics was observed greater under 60%:40%:0%:0%(Sowing,jointing,flowering,and grain filling stage respectively)N fertilization as compared to 50%:50%:0:0(Sowing,jointing,flowering,and grain filling stage respectively).N fertilization improved the photosynthetic traits(Gs,Pn and Tr)and biomass characteristics which then ultimately improved the grain yield.(4)In contrast to control,225 kg ha^-1augmented the photosynthetic rate and total chlorophyll by 20.57%and 50.28%,respectively.Winter wheat under 225 kg ha^-1had significantly 149.28%and 54.39%higher nitrogen uptake and use efficiency than other treatments.Moreover,nitrogen nutrition with 225 kg ha^-1demonstrated the maximum grain yield(7316.63 kg ha^-1)and leaf area index(6.31)of winter wheat crop.Grain yield of winter wheat had a significant positive correlation with N uptake,N use efficiency,chlorophyll contents,and growth components.(5)Total chlorophyll,SPAD and chlorophyll carotenoids were also improved after the nitrogen fertilization.SPAD increased 20.00%at jointing,13.62%at flowering and 11.89%at grain filling stage under 225 kg ha^-1at 60%:40%:0%:0%(Sowing,jointing,flowering,and grain filling stage respectively)N compared to other treatments.Chlorophyll a and chlorophyll b with 225 kg N ha^-1had significantly increase by 48.12%and 65.57%,respectively than other treatments.While total chlorophyll and chlorophyll carotenoids were observed higher with 225 kg N ha^-1where plants received 60%nitrogen at sowing and 40%at jointing stage.(6)Findings of present study indicated that nitrogen nutrition significantly enhanced the growth,biomass,yield components of winter wheat.Growth and yield components were augmented under 225 kg N ha^-1and 300 kg N ha^-1where nitrogen was applied 60%at sowing and 40%at jointing stage as related to other treatments.Biological yield,N uptake,protein contents were also noted higher under 225 kg N ha^-1and 300 kg N ha^-1at jointing and flowering stage.Moreover harvest index,N use efficiency were observed higher under 150kg N ha^-1and nitrogen harvest index were recorded higher under 300 kg N ha^-1at jointing and grain filling stage where N fertilizer was applied at 50%at sowing and 50%at jointing in both years.Positive significant relationships between grain yield and yield traits were also observed in our study.Grain yield was significantly associated growth,photosynthetic traits,Chlorophyll contents,biological yield,harvest index,N contents,N uptake,N use efficiency and protein contents.In conclusion,the nitrogen dose of 225 kg ha^-1and the proportion of 60%:40%:0%:0%(quantity applied at sowing,at jointing,flowering and grain filling stage)effectively promoted the biomass traits,photosynthetic characteristics,nitrogen uptake,yield components of winter wheat.Based on the necessity of both agronomical and physiological characteristics,225 kg N ha^-1was satisfactory to provide sufficient biomass and photosynthetic characteristics to achieve high yield.Therefore,this study significantly reported the effects of different nitrogen rates and ratios on agronomical and physiological traits on winter wheat in Shanxi China.In addition this combination of growing stages,nitrogen doses and ratio could meritoriously increase the grain yield of winter wheat.