Effects Of Nitrogen Fertilizer Reduction On Grain Yield And Quality Of Strong Gluten Wheat

In order to study the effect of nitrogen（N）fertilizer reduction on the yield and quality of strong gluten wheat,and to clarify the regulation mechanism of N application rate affecting dry matter accumulation and transport and N utilization rate of strong gluten wheat,a field experiment was set up for two consecutive years from2020 to 2022.Two strong gluten wheat varieties Jinnong 7（high N efficient type）and Zhongmai 998（high N inefficient type）were selected as experimental materials,and four N application rates of 0 kg·hm^-2（N₀）,180 kg·hm^-2（N₁）,210 kg·hm^-2（N₂）and240 kg·hm^-2（N₃）were set.The effects of N fertilizer reduction on SPAD value of strong gluten wheat leaves,canopy light interception,dry matter accumulation and transport,N absorption and utilization,and the regulation mechanism of wheat grain yield and quality were studied,and the correlation analysis was carried out.When the nitrogen application rate was reduced from N₃ to N₂,the number of spikes per unit area of the two strong gluten wheat varieties decreased significantly with the decrease of nitrogen application rate,and the grain yield of the two varieties was significantly affected.There was no significant decrease in grain yield and1000-grain weight.The interaction between variety and nitrogen application rate had significant effects on grain yield and yield components.The partial factor productivity of nitrogen fertilizer of Jinnong 7 was higher than that of Zhongmai 998under all nitrogen application treatments.Reducing nitrogen to N₂ had no significant effect on nitrogen harvest index and nitrogen use efficiency of Jinnong 7,while nitrogen harvest index and nitrogen use efficiency of Zhongmai 988 increased significantly.The total number of stems and the average number of panicles per plant of 2strong gluten wheat varieties and the canopy photosynthetically active radiation interception（IPAR）,canopy photosynthetically active radiation transmittance（CaR）,canopy photosynthetically active radiation reflectance（PeR）,leaf SPAD value,length,width and leaf area decreased with the decrease of N application rate.The SPAD value of Zhongmai 998 decreased more than that of Jinnong 7 after anthesis,and the effect of N application on the light interception ability of high N efficient strong gluten wheat varieties was better than that of low N efficient varieties.N application could alleviate the senescence rate of flag leaf,top 2^nd leaf and top 3^rd leaf in the late growth stage of wheat to a certain extent.Appropriate reduction of N fertilizer to N₂treatment had no significant effect on canopy light interception of strong gluten wheat.Reducing the amount of N application significantly reduced the dry matter accumulation and N accumulation in various organs of the two strong gluten wheat varieties at anthesis and maturity,and the grain yield was mostly derived from the dry matter accumulation after anthesis,and the leaves were the main nutrient organs for the dry matter transport before anthesis of the N efficient varieties,and the dry matter transport before anthesis of the N inefficient varieties was derived from the leaves and stems+sheaths,and the N accumulation and N distribution ratio at maturity were expressed as grains>stems+sheaths>leaves>spike axis+glumes,and the grain N accumulation was mostly derived from the N transport before anthesis.There was no significant decrease in dry matter and N accumulation in various organs at maturity stage when N fertilizer was reduced to N₂.The pre-anthesis dry matter and N transport amount,transport rate and contribution rate to grain of leaves and ears decreased significantly,while stems+sheaths was the opposite.The contribution rate of dry matter and N accumulation to grain after anthesis increased significantly in both varieties.The protein and component content,starch and component content,flour wet gluten content,gluten index and sedimentation value of strong gluten wheat grains decreased with the decrease of N application rate.Under each N application treatment,the other indexes of Jinnong 7 were higher than those of Zhongmai 998.The decrease of N application rate from 240 kg·hm^-2 to 210 kg·hm^-2 did not lead to a significant decrease in grain quality of strong gluten wheat.In summary,N application rate had significant effects on light interception characteristics,dry matter accumulation and transport,N accumulation and transport,and N use efficiency of two strong gluten wheat varieties.Appropriate reduction of N fertilizer had no significant effect on grain yield and quality,canopy light interception characteristics,dry matter and N accumulation and transport,and N reduction increased N harvest index and N use efficiency of N inefficient varieties.Under the conditions of this experiment,reducing N fertilizer to 210 kg·hm^-2 can maintain stable yield of strong gluten wheat while ensuring quality.