Effects And Physiological Mechanisms Of Nitrogen Application Levels On Nitrogen Uptake And Utilization Of Different Nitrogen-efficiency Maize Varieties

Maize production occupies an important position in our country and the world,and is very important to ensure food security.There are problems such as low utilization rate of chemical fertilizers and excessive application of nitrogen fertilizers in corn planting in my country,and there is great potential for saving nitrogen and increasing efficiency.In this study,Zhengdan 958,Lianchuang 808,Denghai 605,Keyu 188,Jingnongke 728,and Dika653 were used as the tested varieties,and five cultivars of 0,120,180,240,and 360kg·hm-2 were set.The field experiment of nitrogen level studies the effect of nitrogen fertilizer dosage on the growth and development,nitrogen utilization,root system characteristics,leaf photosynthetic characteristics and physiological indicators of different varieties of jade,aiming to clarify the differences and physiological mechanisms of different nitrogen use efficiency corn varieties,and for nitrogen efficient the selection of maize varieties and the improvement of maize nitrogen utilization efficiency provide theoretical and technical support.The main research results are as follows:1.Under the conditions of this study,according to the average yield of the six tested varieties under no nitrogen(N0)and high nitrogen(N360)treatments,the representative varieties with double high efficiency type is Keyu 188;the representative variety of double low efficiency type is Zhengdan 958.Among them,under the conditions of no nitrogen(N0),medium nitrogen(N180),and high nitrogen(N360),the average yield of Keyu 188 reached 10.21,11.05,and 13.32 t·hm-2,respectively.The control variety Zhengdan 958 increased production by 12.2%,6.4% and 19.8%.2.The nitrogen uptake efficiency of the two varieties had different responses to nitrogen application rate.Under the condition of no nitrogen application,the average nitrogen uptake of Keyu 188 was 6.5% higher than that of Zhengdan 958;the average nitrogen uptake efficiency was also 26.3% higher than that of Zhengdan 958 under high nitrogen conditions(N180~N360).The accumulation of nitrate nitrogen in the 0-90 cm soil layer under N240 treatment at the harvest period was smaller than that of Zhengdan958;the average accumulation of ammonium nitrogen in each nitrogen application treatment in the 30-90 cm soil layer was higher than that of Zhengdan 958.15.2% lower.The average nitrogen partial productivity under each nitrogen fertilization treatment was7% higher than that of Zhengdan 958.At the same time,compared with Zhengdan 958,the nitrogen use efficiency(grain yield/nitrogen accumulation)of Keyu 188 was lower.It can be seen that Keyu 188 is a high-efficiency nutrient absorption variety.3.The dry matter accumulation of nitrogen-efficient corn variety Keyu 188 was higher than that of Zhengdan 958 in each growth period,and the dry matter accumulation in jointing,large-flare,silking,grain-filling and mature stages was two years(2019 and2019).2020)is 16.35%,11.35%,8.75%,15.95%,7.35% higher than Zhengdan 958 on average.Keyu 188 still maintained a high dry matter accumulation rate 40-50 days after the start of grain filling;the dry matter accumulation after the silking period was significantly higher than that of Zhengdan 958,accounting for a larger proportion of the total dry matter accumulation,which had a significant impact on the yield.contribution rate is higher.4.There were differences in the response of root architecture of maize varieties with different nitrogen efficiencies to nitrogen application rates.The fibrous roots of Keyu 188 are more developed,and the proportion of total root weight is higher than that of Zhengdan 958;especially the second to fourth rounds of root system are more developed,and the proportion of total root fresh weight is 10.6% higher than that of Zhengdan 958 on average.Nitrogen application significantly expanded the root angle of Keyu 188,and the average root angle increased by 13.11% compared with Zhengdan 958,and the root width was larger under the high nitrogen application treatments of N240~N360.5.The chlorophyll content of the ear chlorophyll of the nitrogen-efficient maize variety Keyu 188 at the silking and grain filling stages was significantly higher than that of Zhengdan 958,and the SPAD value of the non-nitrogen treatment at the harvesting stage remained at a high level;The activities of nitrite reductase(Ni R)and nitrate reductase(NR)in ear leaves at silking stage and nitrate reductase(NR)activity at grain filling stage were significantly higher than those of Zhengdan 958.This enables Keyu 188 to ensure strong photosynthetic capacity of functional leaves in the late growth stage,promote dry matter accumulation,and ensure high yield.