| Excessive nitrogen?N?fertilizer input to increase wheat?Triticum aestivum L.?yield may cause some environmental problems,the soil harden and leaned especially.A field experiment was conducted to study the effects of reduced nitrogen application and supplemental irrigation on the light environment,photosynthetic characteristics,dry matter accumulation,nitrogen accumulation and distribution ?water consumption characteristic and yield components in high-yield wheat population for two growth seasons?2013-2015?.The treatments include three irrigation schedules [no irrigation?W1?,medium irrigation?W2,the soil relative water content of 70%±5% after jointing stage?,wellirrigation?W3,the soil relative water content of 85%±5% after jointing stage?] and three nitrogen application levels [no nitrogen?N1?,reduced nitrogen(N2,195 kg N·hm-2),high nitrogen(N3,270 kg N·hm-2)].These results helped to provide basis and guidance for attaining high yield and high efficiency in winter wheat.FThe main results are as follows.1.Effects of reduced nitrogen application and supplemental irrigation on population quality of winter wheatThe tillers number in different treatments was increased gradually with the development process of winter wheat,and reached the maximum value at Jointing stage,and then the tillers number decreased rapidly.Under W2 and W3,the tillers number was increased with the increase of nitrogen application,and populationbefore Jointing period in high nitrogen?N3?treatments were significantly higher than other treatments,while the difference was not significant between the treatments of N3 and N4 at maturity.The N2W2 treatment significantly improved spikelet bearing number.LAI of winter wheat changed as a curve and its peak emerged at booting stage.The leaf area index?LAI?under the condition of N2W2 was the highest among all treatments tested,the LAI decreased slowly at grain filling stage and the period with higher LAI values?>7.6—7.9?was 3-4 days longer than that of high-nitrogen and non-nitrogen treatments,as well as,the leaf photosynthetic potential were 3.6%?3.7% higher than that of N3 in two years,and the photo-synthetically active radiation?PAR?and the light transmission rate at the region of 20-30 cm from canopy was increased by 34.5% and 10.8%,respectively,when compared with the high nitrogen-supplementary water treatments?N3W2?N3W3?.2.Effects of reduced nitrogen application and supplemental irrigation on photosynthetic characteristics of winter wheatAt N2 and N3 treatments under W2 condition,the content of Chl?a+b?and photosynthetic rate?Pn?in flag leaves were significantly higher than N1,but without significant difference between N2 and N3,and Chl?a+b?content and the photosynthetic rate were highest among all treatments tested at grain filling stage.At N2 treatments under W2 and W3 condition,gradually increases of net photosynthetic rate?Pn?,stomatal conductance?Gs?and transpiration rate?Tr?in flag leaves were higher than other treatments,respectively;also intercellular CO2 concentration?Ci?reducing rate,which ranked as N2>N3>N1.In reduced nitrogen and suitable soil moisture treatment?N2W2?,photosynthetic parameters performed perfect at anthesis stage,the maximum net photosynthetic rate?Pnmax?up to 33.20?mol CO2·m-2·s-1 and light saturation point?LSP?up to 1507.4?molm-2·s-1,increased by average 14.5% and 1.2% than other treatments,respectively;but light compensation point?LCP?reaching at the lowest point.3.Effects of different irrigation and nitrogen treatments on dry matter and nitrogen accumulation and transportation and utilization of winter wheatThe results showed that dry matter accumulation amount in the vegetative organsabove ground?stem and leaf?was increased gradually with the development process of winter wheat,and the transportation rate of storages increased with increasing irrigation at pre-anthesis,and reached the maximum value at anthesis.At W1,W2 treatments,the transportation rates of storages to grain under N2 condition were the highest at pre-anthesis and post-anthesis,respectively,but the biggest contribution rate under W3 irrigation condition was N1 treatment.The transportation and contribution rate of storages to grain between N2 and N3 treatments at pre-anthsis presented W2 >W3,except that contribution rate of storages at N3 treatment was W3>W2 before anthsis but transportation amount increased with the increasing of irrigation.Results indicated that the transportation amount of vegetative organs when nitrogen had been applied were significantly higher than of no nitrogen application in different irrigation treatments,and the transportation rate of storages to seed increased with the increasing of nitrogen application at post-anthsis,except for N2>N3 in W1 treatment;in which there was no significant difference between N2 and N3.Against,nitrogen recovery use efficiency?RE?,agronomic efficiency and partial factor productivity of applied were increased with the increase of nitrogen application in N2 and N3 treatments?but W3 irrigation,nitrogen agronomic efficiency was N3>N2?.Under N2 treatment,recovery use efficiency and agronomic efficiency W2>W1>W3,in addition,partial factor productivity of applied and the nitrogen harvest index showed W2>W3>W1.Under the treatment of N2W2,nitrogen recovery use efficiency and partial factor productivity of applied were increased by 10% and 15.33%,respectively,when compared with the high nitrogen-supplementary water treatments?N3W2?N3W3?.4?Effects of different irrigation and nitrogen treatments on senescence of the flag leave in wheatResults showed that it was obvious effect of nitrogen-irrigation on the activites of SOD enzyme,POD enzyme and the MDA content in winter wheat flag leaf.The activity of SOD decreased slowly,and showed N1>N2>N3 trend except that there was no significant difference between N2 and N3 at 7d after anthesis;The dynamic trend of POD activity in flag leaf was a single-peak curve,the maximum appeared at 14 d after anthesis,then reduce rapidly which was N1>N2>N3 in both W1 and W3,but the minimum decreasing margin was in W2N2.Therefore,irrigation and nitrogen application affected the delay on reducing of SOD?POD enzyme activities,especially enzyme activities in W2N2 treatment maintained a higher level,which had an obvious effect of flag leaf function on delaying senescence.MDA content of wheat flag leaf in functional period increased as the stages went on,which rise presented N1>N2>N3 in both W1 and W3 irrigation and N1>N3>N2 in W2 irrigation;5.Effects of different irrigation and nitrogen treatments on water use efficiency and yield in winter wheatThe wheat water use efficiency in W2 was the highest,significantly higher than that in W3;Taken irrigation and nitrogen application for two consecutive years in W2N2,wheat water use efficiency increased by 14.5%,spike number increased with the increase of nitrogen application,reached significant level.Unlike,spike number in W3 irrigation was remarkable higher than that in W1 and W2,and increased with the increase of nitrogen application;in addition,spike number and 1000-grain weight of N2 treatment in 2013-2014 performed best,but that of N3 treatment in 2014-2015 was best.Spike number of two consecutive years under N2 treatment increased with the increasing of the increasing amount,and there was obvious significant difference between W1,W2 and W3 condition.Indeed,in N3 treatment,the maximum spike number and spike grain number appeared at W3 treatment,but the maximum 1000-grain weight at W2 treatment. |
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