Regulation Effect Of Nitrogen Fertilizer Management On Carbon And Nitrogen Metabolism Of Spring Wheat Under Drip Irrigation

The drip irrigation wheat technology has been a planting method for efficient use of water and fertilizer in densely planted crops in Xinjiang.However,the traditional concept of high fertilizer and high yield is still followed during the cultivation of drip irrigation wheat in Xinjiang,resulting in excessive nitrogen fertilizer input and the reduce ofnitrogen efficiency.Therefore,the key of sustainable development of Xinjiang wheat agricultural industry is to explore the characteristic changes of wheat grains during drip filling period and the formation rules of yield and quality under the condition of reduced nitrogen,and simultaneously improve the nitrogen fertilizer utilization rate.In this paper,set 7 different levels of nitrogen application,from the perspective of wheat grain quality formation,under the multi-level treatment of reducing nitrogen and applying organic fertilizer,the grain filling characteristics of drip-irrigated spring wheat,changes in key enzyme activities and accumulation of carbon and nitrogen metabolism in grains,etc.,which are the main contents of the grain bank characteristic development.The analysis explores the regulatory effects of nitrogen reduction and organic fertilizer application on grain filling,and taps the yield and quality potential of spring wheat under drip irrigation,with a view to providing scientific basis for high yield and quality cultivation of spring wheat under drip irrigation in Xinjiang.The main conclusions as follows:1.The dry matter accumulation of stem and sheath,leaves,ears,and grain weight of XC38 and XC49showed that first increased and then decreased with the increase of the degree of nitrogen reduction and organic fertilizer application,under N15 treatment?organic fertilizer replaced 15%nitrogen fertilizer,that is,85%N+15%organic fertilizer?reached the best.The theoretical maximum 1000-grain weight,maximal filling rate and average filling rate of the two varieties also showed that first increased and then decreased with the increase of the degree of nitrogen reduction and organic fertilizer application,and the best performance at the N15 treatment.This indicated that suitable nitrogen reduction and organic fertilizer were beneficial to wheat grain filling process.And compared with the two varieties,the dry matter change of XC38?strong gluten?was more sensitive than that of XC49?medium gluten?under the condition of nitrogen reduction and organic fertilizer application.2.In the filling process of XC38 and XC49,sucrose synthase?SS?,adenosine diphosphate glucose pyrophosphorylase?ADPG-PPase?,soluble starch synthetase?SSS?,granule bound starch synthase?GBSS?and starch branching enzyme?SBE?in wheat grain showed that first increased and then decreased;they peaked at 28 days after flowering.Under different treatments,with the increase of the degree of nitrogen reduction and organic fertilizer application,both varieties performed best at N15,and there were significant differences with other treatments.The SS,ADPG-PPase,SSS,GBSS and SBE at N15 treatments of XC38increased by 7.40%?39.50%,9.90%?56.20%,6.86%?55.97%,3.15%?6.07%,5.74%?54.31%,respectively;SS,ADPG-PPase,SSS,GBSS and SBE at N15 treatments of XC49 were increased by2.93%?31.9%,7.90%?54.14%,5.00%?54.69%,5.72%?15.95%,2.47%?41.80%,respectively.It can be seen that the activity of key enzymes of carbon metabolism of XC38 was more obvious under the conditions of nitrogen reduction and organic fertilizer application.The content of carbon metabolites showed different changes during the filling period;the content of sucrose gradually decreased with the advance of the filling period,and the content of starch showed an increasing change.In different treatments,the sucrose and starch?straight-chain,amylopectin-chain,and total starch?contents of the two varieties showed a trend of first increase and then decrease,and the amylose/amylopectin showed a trend of first decreased and then increased.And all the index performed best at N15.3.As the filling time progressed,the activities of nitrate reductase?NR?,glutamine synthetase?GS?and glutamate pyruvate transaminase?GPT?in wheat grains of two different varieties gradually decreased.In different treatments,with the increase of the degree of nitrogen reduction combined with the application of organic fertilizer,XC38 and XC49 performed best at N15,and there were significant differences from other treatments.The activities of NR,GS and GPT of XC38 under N15 conditions were increased by 3.54%?28.86%,3.23%?38.85%,1.25%?28.48%respectively compared with other treatment.And the activities of NR,GS and GPT of XC49 under N15 conditions were increased by 2.25%?27.39%,1.64%?31.80%,1.20%?21.17%respectively compared with other treatment.During the filling period,appropriate nitrogen reduction combined with organic fertilizer can not only increased the total protein content of the grain,but also improved the protein quality.The protein content of XC38 and XC49 showed increased first and then decreased with the increase of the degree of nitrogen reduction combined with the application of organic fertilizer,which performed best at N15 treatment.From the analysis of different varieties,after flowering 35 days and N15 treatment,the XC38?strong gluten?compared with XC49?medium gluten?increased by 21.67%.The albumin,globulin,gliadin,gluten,and glu/gli ratio in the grains also showed similar trends;under different treatments,N15 treatment was the best.4.Yield composition of wheat of XC38 and XC49 showed increased first and then decreased with the increase of nitrogen reduction and application of organic fertilizer.The 1000-grain weight and spike number of the two varieties performed best at N15,and the grain per spike optimal at N20 processing.And under the condition of nitrogen reduction and combined application of organic fertilizer,the grain yield and protein yield of N15 treatments of the two varieties were larger than those of other treatments,there was no significant difference between N15 and N20 treatments,and there were significant differences with other treatments.After fitting,the grain yield showed a quadratic relationship with nitrogen fertilizer levels:y=-0.0533x²+23.023x+4910.7?XC38,R²=0.9869?,y=-0.052x²+23.141x+4783.6?XC49,R²=0.9934?;that was,when the nitrogen application rate of the two varieties was 255 kg·hm^-2,the yield of XC38 was7315.73 kg·hm^-2,and the yield of XC49 was 7303.26 kg·hm^-2.There was also a quadratic relationship between protein yield and nitrogen fertilizer levels:y=-0.0173x²+6.6221x+522.33?XC38,R²=0.8925?,y=-0.0107x²+4.5175x+454.51?XC49,R²=0.9387?,That is,when the nitrogen application rate of the two varieties is 255 kg·hm^-2,the protein yield of XC38 was 1086.03 kg·hm^-2 and the protein yield of XC49was 910.71 kg·hm^-2.In summary,an appropriate nitrogen reduction and organic fertilizer ratio can not only improve wheat filling characteristics,but also have an important impact on the activity of key enzymes of carbon and nitrogen metabolism,protein,starch and its components and yield.In this experiment,the effect of reduce of nitrogen and applying organic fertilizer on the starch and protein content of XC38?strong gluten type?was more obvious than that of XC49?medium gluten type?.And in different treatment conditions,the optimal combination of nitrogen reduction and organic fertilizer application was N15,which was 85%+15% organic fertilizer.