Effects Of Combined Application Of Controlled-release Urea And Traditional Urea On Growth And Nitrogen Use Efficiency Of Winter Wheat

Wheat is one of the most important food crops in the world,and plays an indispensable role in ensuring food security in China.The application of chemical fertilizer is not only the need of contemporary grain production development,but also the basic guarantee of grain production.Nitrogen fertilizer had the most obvious effect on crop yield,and the application amount was relatively large.In order to improve wheat yield,the application rate of nitrogen fertilizer increased year by year,resulting in environmental pollution and decreased nitrogen utilization rate.In view of the problems of single nitrogen type and low utilization efficiency in winter wheat production in Guanzhong irrigation area,Xiaoyan 22 was used as the test material in this study.Three nitrogen application levels(L:135kg·hm^-2,M:180 kg·hm^-2,H:225 kg·hm^-2)and two nitrogen types（traditional urea TU,traditional urea and controlled-release urea 1:1 combined application CRUTU）were designed to study the effects and mechanism of controlled-release urea and traditional urea combined application on winter wheat growth,lodging resistance,grain filling,yield and nitrogen utilization efficiency under nitrogen reduction to determine the nitrogen management strategy suitable for winter wheat,so as to improve wheat yield and nitrogen utilization efficiency,reduce environmental pollution,and provide technical support for the sustainable production of winter wheat.The main results are as follows:1.Compared with high nitrogen application rate,The plant height of winter wheat decreased by 2.1%～8.5%under medium nitrogen application.Compared with TU,the plant height of winter wheat under CRUTU decreased by 2.1%～6.5%,the total stem number decreased by 1.2%～7.9%,the leaf area index increased by 1.7%～7.1%,and the dry matter accumulation increased by 4.8%～11.3%.2.Compared with high nitrogen application rate,the lodging resistance of medium nitrogen application rate increased by 15.9%～42.5%.Compared with TU,the number of large and small vascular bundles under CRUTU increased by 4.5%～18.0%,and the lignin content increased by 1.8%～12.4%,the folding strength increased by 5.1%～25.5%.Lodging resistance index increased by 5.4%～15.2%.3.Compared with the high nitrogen application rate,the grain weight of weak grains of winter wheat under medium nitrogen application rate increased by 3.4%～9.2%.Compared with TU,CRUTU increased the contents of IAA,ABA and Z+ZR in grains at early grain filling stage,and decreased the content of GA,which was beneficial to the transport of assimilates to grains.By Logistic equation fitting,CRUTU improved the filling duration and average filling rate of winter wheat vulnerable grains,and eventually led to the grain weight of winter wheat vulnerable grains increased by 5.3%～7.7%.4.Compared with high nitrogen application rate,the nitrate content decreased by 3.8%～17.9%,the agronomic efficiency of nitrogen fertilizer（AE_N）was increased by 1.7%～21.3%under medium nitrogen application rate;Compared with TU,CRUTU increased the aboveground nitrogen accumulation and nitrogen translocation in vegetative organs of winter wheat,resulting in an increase in nitrogen harvest index（NHI）by 4.5%～14.5%,soil nitrate content decreased by 4.5%～35.7%,and an increase in 1000-grain weight by 0.9%-2.6%,thereby increasing the yield of winter wheat by 10.50%and 3.41%on average.At the same time,the partial factor productivity（NPF_N）of nitrogen fertilizer under CRUTU increased by0.7%～12.6%,and the agronomic efficiency of nitrogen fertilizer（AE_N）increased by 3.4%～29.2%.5.Under the combined application of controlled-release urea and traditional urea,the reduction of 20%(is 180 kg·hm^-2)nitrogen application rate on the basis of conventional nitrogen application rate(225 kg·hm^-2)in Guanzhong irrigation area is conducive to improving agricultural pollution and agricultural resource waste and improving nitrogen utilization efficiency,which is conducive to the sustainable production of winter wheat.