Effect Of Nitrogen Reduction And Application By Stages On Yield And Nitrogen Use Efficiency In Wheat

The experiment was carried out from 2016 to 2017 under field conditions in the Xuanzhuang village,Tai an,Shandong Province,the breed is winter wheat cultivar Shannong29.Respectively in the powder loam?F?and sandy loam?S?plots,set the nitrogen application rate and nitrogen application times two factors test,Nitrogen application levels were set at240 kg hm^-2?traditional nitrogen application,N1?,192 kg hm^-2?nitrogen application reduction by 20%on the basis of traditional nitrogen application,N2?and 144 kg hm^-2?nitrogen application reduction by 40%on the basis of traditional nitrogen application,N3?.Nitrogen application times were 1 application of nitrogen fertilizer?basic application of nitrogen fertilizer,D1?,application of 2 times of nitrogen fertilizer?nitrogen application at sowing+jointing,nitrogen application ratio of 5:5,D2?,and 3 application of nitrogen fertilizer?sowing+jointing+anthesis,nitrogen application ratio of 5:3:2,D3?,with no nitrogen application as CK during the whole growth period?N0?.Research the effects of nitrogen reduction and application by stages on yield and nitrogen use efficiency in wheat,to provide a theoretical basis and technical support for the green high-efficient cultivation of winter wheat in different textures.The main results are as follows:1 Effect of nitrogen reduction and application by stages on NO₃^-N time-space distribution in soilIn the powder loam plots,nitrogen fertilization was located for two consecutive years,NO₃^-N content of each soil layer in each growth stages showed N1>N2,the NO₃^-N content of each soil layer in each growth stage before jointing and maturity stage was D3>D2;Under the condition of N1,the NO₃^-N content of 0-30cm and 100-200cm soil layer at anthesis was D2>D3,and there was no significant difference in other soil layer;Under the condition of N2,the NO₃^-N content of each soil layer at anthesis was D2>D3.The results indicated that soil nitrogen supply was high before the jointing stage of D3 treatment,and soil nitrate content in each soil layer gradually decreased with the growth process progressed of wheat,resulting in a decrease in the supply of nitrogen to the upper layer from the jointing to the anthesis stages.Especially under the condition of reducing nitrogen application rate,the supply of nitrogen in the upper layer of soil from jointing to anthesis was insufficient,the number of degenerate florets increased,and the number of grains per spike decreased significantly.In the sandy loam plots,NO₃^-N content of soil decreased significantly with the decrease of nitrogen application rate at each growth stage.There was no significant difference between the soil NO₃^-N e content in the D2 treatment and the D3 treatment before the jointing stage,the NO₃^-N content in each soil layer was D2>D3 during the anthesis period;The soil NO₃^-N content in 0-40cm and 80-200cm soil layers at mature stage showed D3>D2.There was no significant difference in soil NO₃^-N content in 40-80cm soil layer D2 and D3 treatments.The results indicated that D2 treatment increased the soil nitrogen supply from the jointing stage to the anthesis stage compared with D3 treatment;With reduced nitrogen application rate,soil nitrogen supply from jointing stage to anthesis stage of D3 treatment was insufficient,grain number per spike was significantly decreased,nitrogen uptake and utilization of topdressing plants at anthesis were less,and soil nitrogen residue increased.2 Effect of nitrogen reduction and application by stages on wheat grain yield and nitrogen use efficiencyIn the powder loam plots,the first year of 2015-2016 nitrogen application experiment,grain yield was N1,N2>N3,under the same N application rate,the panicles showed D1?D2,D3,and the 1000-grain weight was D2,D3?D1,there was no significant difference in the grain yield of each N application period.The results indicated that in the powder loam plots,compared with the nitrogen application in different N application stages under the same nitrogen application,compared with the 20%reduction in nitrogen application rate,the winter wheat grain yield did not change significantly.In the powder loam plots,nitrogen fertilization was located for two consecutive years,under D1 and D2 conditions,the grain yield was N1?N2>N3,and the N recovery efficiency?NRE?was N1>N3.Under the condition of D3,the grain yield was N1?N2,N3,and NRE was N1>N2>N3.Under N2 and N3 conditions,the grain yields were D2?D1,D3,and NRE were D2>D3>D1.The results indicated that under the condition of 50%N application at sowing and 50%N application at the jointing stage,a 20%reduction in nitrogen application rate can still maintain higher yield levels and nitrogen recovery efficiency.Under the condition of reduce the proportion of nitrogen applied during the jointing stage and insufficient nitrogen supply,even if the ratio of nitrogen application at anthesis was increased,the grain yield and nitrogen recovery efficiency still decreased significantly,and the rate of yield reduction was 11.24%.In the sandy loam plots,grain yield was N1?N2?N3,nitrogen agronomic efficiency and nitrogen recovery efficiency were N1?N2,N3.Under the condition of N1,the grain yield was D2,D3?D1.The nitrogen agronomy efficiency and nitrogen recovery efficiency of D3 treatment were significantly lower than that of D2 treatment.The results indicated that in the sandy loam plots,reduced nitrogen application not only results in lower yield,but also lower nitrogen agronomic efficiency and nitrogen recovery efficiency;under the traditional nitrogen application rate,50%of N application at sowing and 50%of N application at the jointing stage can obtain higher grain yield and nitrogen recovery efficiency.3 Effect of nitrogen reduction and application by stages on senescence of wheat flag leavesIn the powder loam plots,nitrogen fertilization was located for two consecutive years,under the condition of D1,reducing the amount of nitrogen applied to accelerate the senescence of flag leaf.Under the conditions of D2 and D3,the 20%reduction of nitrogen application had no significant effect on the senescence characteristics of the flag leaf at the filling stage.Under the same nitrogen application rate,the activity of flag leaf SOD,CAT activity and soluble protein content were all at D3>D2>D1 during grain filling stage,the MDA content in flag leaf was opposite.The results showed that both D2 and D3 treatments could increase the nitrogen supply intensity of post-anthesis soil and delay the senescence of flag leaf.Nitrogen application at anthesis was more favorable for delaying the senescence of flag leaf.In the sandy loam plots,under the conditions of D1 and D2,reducing the amount of nitrogen applied to accelerate the senescence of flag leaf,under the condition of D3,the 20%reduction of nitrogen application had no significant effect on the senescence characteristics of the flag leaf at the filling stage.Under the same nitrogen application rate,the activity of flag leaf SOD,CAT activity and soluble protein content were all at D3>D2>D1 during grain filling stage,the MDA content in flag leaf was opposite.The results showed that nitrogen application at anthesis was more favorable for delaying the senescence of flag leaf,which is consistent with the law of powder loam plots.4 Effect of nitrogen reduction and application by stages on photosynthetic characteristics,dry matter accumulation and distribution of wheatIn the powder loam plots,nitrogen fertilization was located for two consecutive years,SPAD values,Pn,Gs and?_PSIISII of flag leaves decreased significantly with the decrease of nitrogen application amount after anthesis under D1 condition,the distribution amount of assimilate to grain after anthesis showed N1>N2,N3.the nitrogen application amount decreased by 20%had no significant effect on the photosynthetic characteristics of flag leaves,and the distribution amount of assimilated matter to grain after anthesis was N1,N2>N3under D2 and D3 condition.Under the same N application amount,SPAD values,Pn,Gs,and?_PSIISII of the flag leaf at the filling stage all showed D3>D2>D1,the contribution rate of the post-anthesis assimilate matter to grain was shown as D2,D3>D1 under N1condition,and showed as D3?D2?D1 under N2 and N3 conditions.These results indicated that photosynthesis assimilatory capacity of flag leaves and contribution of Post-anthesis assimilate to grain after nitrogen topdressing at anthesis significantly increased under the condition of nitrogen application reduced by 20%,and which of basis on nitrogen application at sowing and jointing.In the sandy loam plots,SPAD values,Pn,Gs and?_PSIISII of flag leaves and assimilate accumulation after anthesis decreased significantly with the decrease of nitrogen application rate under the condition of D2 and D3.Nitrogen application reduction by 20%had no significant effect on the photosynthesis assimilational capacity of flag leaves under D3condition.Under the same N application amount,SPAD values,Pn,Gs,and?_PSIISII of the flag leaf at the filling stage all showed D3>D2>D1,the contribution rate of the post-anthesis assimilate matter to grain was shown as D2,D3>D1 under N1condition,and showed as D3?D2?D1 under N2 and N3 conditions.These results indicated that under the condition of large proportion of nitrogen supply in the early wheat growth period,decreasing N application rate,flag leaf's ability to contract significantly reduced.However,under the condition of low nitrogen application rate at the early growth stage,the proportion of nitrogen applied during the jointing stage was reduced,and flowering was increased,the proportion of nitrogen applied during the period is conducive to improving the ability of post-flowering leaves to contract light.5 Effect of nitrogen reduction by stages on the accumulation and distribution of nitrogen assimilation in PlantsIn the powder loam plots,nitrogen fertilization was located for two consecutive years,population nitrogen accumulation and nitrogen transfer in vegetative organs at anthesis and maturity decreased significantly with decreasing nitrogen application under positioning application of nitrogen with second year.The NR and GS activities in flag leaves decreased significantly after anthesis under the condition of nitrogen application reduced by 20%,and N accumulation after anthesis and contribution of N accumulation in vegetative organs to the grain were N1>N2,N3 under D1 condition.The nitrogen application amount decreased by20%had no significant effect on the activity of nitrogen-related enzymes after anthesis,and N accumulation after anthesis and contribution of N accumulation in vegetative organs to the grain were N1,N2>N3 under D2 and D3 condition.Under the same N application amount,NR and GS activities in flag leaves all filling stages all showed D3?D2?D1,the contribution rate of the post-anthesis nitrogen assimilation to grain was shown as D2,D3>D1under N1condition,and showed as D3?D2?D1 under N2 and N3 conditions.Nitrogen accumulation and nitrogen transfer in vegetative organs at anthesis and maturity at anthesis and maturity showed as D2,D3?D1,N accumulation after anthesis and contribution of N accumulation in vegetative organs to the grain were D2,D3?D1.These results indicated that and nitrogen assimilation of flag leaves after nitrogen topdressing at anthesis significantly increased basis on nitrogen application at sowing and jointing,however,nitrogen accumulation and the contribution rate of the post-anthesis nitrogen assimilation to grain did not increase significantly.In the sandy loam plots,nitrogen accumulation and nitrogen transfer in vegetative organs at anthesis and maturity decreased significantly with decreasing nitrogen application.The activity of nitrogen-related enzymes was significantly decreased,but there was no significant difference in the contribution rate of the post-anthesis nitrogen assimilation to grain in D1and D2 conditions under the condition of nitrogen application reduced by 20%.Nitrogen application reduction by 20%had no significant effect on the activities of nitrogen assimilation-related enzymes and the contribution of post-anthesis nitrogen assimilation to grain.Under the same nitrogen application rate,the activity of flag leaf NR and GS activity were all at D3>D2>D1 during grain filling stage,nitrogen accumulation at anthesis and maturity showed D2,D3>D1,there was no significant difference in the contribution rate of nutrient nitrogen to grain nitrogen after anthesis in each treatment.This indicated that the shortage of nitrogen fertilizer was not conducive to the absorption and accumulation of nitrogen in winter wheat.Although nitrogen application at anthesis can significantly increase the nitrogen assimilation ability of flag leaves after anthesis,there was no significant change in nitrogen accumulation during the maturation period,which was related to the jointing stage.This is related to the decrease in population due to insufficient supply of nitrogen during the jointing period.