Effects Of Nitrogen-saving Cultivation On Root Traits And Population Structure In Drip Irrigation Study Of Regulatory Effects

The concept of traditional high-yield and high-fertilizer still persists in the production of drip-irrigated spring wheat in Xinjiang.Nitrogen fertilizer is used in excess and nitrogen efficiency is low.Therefore,studying the changes of wheat high-yield population structure under low nitrogen conditions is of great significance for the efficient production of wheat in Xinjiang.Therefore,from the perspective of the development of crop populations,this paper studied the changes of root morphology and physiological characteristics under root nitrogen reduction and its relationship with the characteristics of the source and sink characteristics of plant shoots,and explored the effects of reducing nitrogen through the root layer and regulating root growth and canopy population characteristics.The mechanism of production,storage and transport of spring wheat under drip irrigation and the law of yield formation were revealed.The best mode of nitrogen application was sought in order to provide a scientific basis and technical support for further stabilizing the yield of spring wheat in drip irrigation in Xinjiang and increasing nitrogen use efficiency.The main conclusions are as follows:1.The root morphology,root length density,root volume and root mass of spring wheat under drip irrigation increased first and then decreased with the increase of nitrogen application rate.The results showed that Xinchun 31 had the best morphological characteristics of N2(275 kg·hm^-2)root system,and the root mass was 48.3 g,root length density was 3.539 cm·cm^-3,and Xinchun 6 was N3(250kg·hm^-2)flowering stage had the best morphological characteristics.The root mass was 49.3 g and the root length was 4.066 cm·cm^-3at the flowering stage.Xinchun No.6 N3 performed well,and the root quality,root length density,and root volume were increased by 2.07%,14.89%,and 16.69%compared with the treatment of N2(275 kg·hm^-2)of Xinchun No.31,and the morphological characteristics and yield of the roots were determined.Correlation studies showed that root mass,length,and volume of wheat were significantly correlated with grain yield during flowering.Under different nitrogen application rates,when the nitrogen application rate of Xinchun31 reached N2,the physiological characteristics of roots performed best when the nitrogen application rate of Xinchun6 reached N3.The physiological characteristics of root system of Xinchun No.6 performed well.The root POD activity,root glutamine synthetase activity,root nitrate reductase activity,and root activity increased by 0.22%,6.15%,16.12%,and 8.08%,respectively,compared with Xinchun 31.The content of MDA in the roots of Xinchun 31 increased by 6.94%compared with that of Xinchun 6.The correlation between root physiological characteristics and yield showed that there was a significant positive correlation between root enzyme activity and vigor and yield.There was a significant negative correlation between MDA content and yield.It can be seen from the correlation coefficient between yield and root physiological characteristics.The relationship between glutamine synthetase,nitrate reductase and root vigor and yield was stronger under nitrogen treatment,and root activity had the highest correlation with spring wheat yield（r=0.987**）.2.Under different nitrogen treatments,the suitable amount of nitrogen could increase the total stem number of spring wheat in drip irrigation,increase the number of harvest and the percentage of stem and tiller,and the total number of stems could be reduced by high or low nitrogen application.The study showed that the Xinchun of N2(275 kg·hm^-2)was the best.The total stem number of the flowering period was 706.67×10⁴·hm^-2,the stem and tiller percentage reached 79.19%,the leaf area index was 7.7,the post flower dry matter contribution rate was 75.04%,the grain number leaf ratio and the grain weight leaf ratio were also reached to 4215.8 grain·m^-2,199 g·m^-22 respectively.The Xinchun of N3(250 kg.hm^-2)was the best.The total stem number of the flowering period was 720.67×10⁴·hm^-2,the stem and tiller percentage reached 75.91%,the leaf area index was 6.8,the post flower dry matter contribution rate was 75.52%,the grain number leaf ratio and the grain weight leaf ratio were also reached to the highest score of 4233.2grain·m^-2,203.9 g·m^-2.The contribution rate of dry matter after the N3 of Xinchun 6,the number of grain number Yeby and the grain weight leaf compared with the Xinchun 31 N2 treatment increased 0.6%,0.4%,2.5%.Through the study on the correlation between the population structure and the yield,it showed that the percentage of stem and tiller percentage,the contribution rate of dry matter after the flower and the yield were significantly correlated with the yield,and the grain Yeby,grain weight ratio and yield were significantly related to the yield.The correlation coefficient of yield and agronomic traits of spring wheat showed that the correlation of leaf area index and grain leaf ratio and grain yield under different nitrogen treatments were both strong,and leaf area had the highest partial correlation to yield of spring wheat(r=0.856^**).3.The Pn,Tr and Gs of spring wheat leaves increased first and then decreased with the increase of nitrogen application rate.Ci showed the opposite trend.The results showed that the Xinchun at N2(275kg·hm^-2)reached the highest rate of 26.21μmol·m^-2·s^-1,stomatal conductance 0.79 mol·m²·s,and transpiration rate 7.61mmol·m²·s.the Xinchun at N3(275 kg·hm^-2)reached the highest rate of26.67μmol·m^-2·s^-1,stomatal conductance 0.82 mol·m²·s,and transpiration rate 7.81mmol·m²·s.the leaf fluorescence parameters（Fv/Fm）and SPAD value of drip irrigation spring wheat increased first and then decreased with the increase of nitrogen application.The highest value of Fv/Fm and SPAD at flowering stage was 0.88 and 53.5 respectively,and the peak of Fv/Fm and SPAD reached 0.91 and 55.8 at the N3flowering stage,respectively.The correlation between leaf photosynthetic characteristics and yield showed that the Pn,Gs,Fv/Fm and SPAD values were positively correlated with yield,and Ci was negatively correlated with yield.From the correlation coefficient of yield and leaf photosynthetic characteristics,the correlation of net photosynthetic rate,fluorescence parameter and SPAD value to yield under different nitrogen treatments could be seen.All of them were relatively strong,and net photosynthetic rate had the greatest influence on the yield of spring wheat,with a partial correlation coefficient of 0.778^*.4.The yield and yield components of the two varieties increased with the increase of nitrogen application,and then increased first and then decreased.The maximum number of spike number,grain number per spike and 1000 grain weight of N2(275 kg·hm^-2)reached to 432×10⁴·hm^-2,40.48,47.23 g,respectively,and the number of spikes,grain numbers and 1000 grain weight of N3(250 kg·hm^-2)were reached respectively.The highest was 427×10⁴·hm^-2,39.19,46.80 g.The correlation analysis and path analysis of the yield composition showed that the effect of 1000 grain weight on the yield of spring wheat in drip irrigation was the greatest,and the overall performance was 1000 grain weight>ear number>spike grain number;the number of spike grain number was the most direct effect on yield,and the total number of spike grain number>ear number>1000 weight.The yield of XinChun 31 was N2 and the highest yield was 7111.1 kg·hm^-2.The yield of Xin Chun 6 reached 7522.9 kg·hm^-2.The nitrogen application and yield of the two varieties were two parabola function relations,and the XinChun 31 showed that when the nitrogen application amount was 286 kg·hm^-2,the XinChun 6 showed the highest yield when the nitrogen fertilizer application was 258 kg·hm^-2.